Publications by authors named "Wolfgang A Tomé"

176 Publications

Individualized quality of life benefit and cost-effectiveness estimates of proton therapy for patients with oropharyngeal cancer.

Radiat Oncol 2021 Jan 21;16(1):19. Epub 2021 Jan 21.

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.

Background: Proton therapy is a promising advancement in radiation oncology especially in terms of reducing normal tissue toxicity, although it is currently expensive and of limited availability. Here we estimated the individual quality of life benefit and cost-effectiveness of proton therapy in patients with oropharyngeal cancer treated with definitive radiation therapy (RT), as a decision-making tool for treatment individualization.

Methods And Materials: Normal tissue complication probability models were used to estimate the risk of dysphagia, esophagitis, hypothyroidism, xerostomia and oral mucositis for 33 patients, comparing delivered photon intensity-modulated RT (IMRT) plans to intensity-modulated proton therapy (IMPT) plans. Quality-adjusted life years (QALYs) lost were calculated for each complication while accounting for patient-specific conditional survival probability and assigning quality-adjustment factors based on complication severity. Cost-effectiveness was modeled based on upfront costs of IMPT and IMRT, and the cost of acute and/or long-term management of treatment complications. Uncertainties in all model parameters and sensitivity analyses were included through Monte Carlo sampling.

Results: The incremental cost-effectiveness ratios (ICERs) showed considerable variability in the cost of QALYs spared between patients, with median $361,405/QALY for all patients, varying from $54,477/QALY to $1,508,845/QALY between individual patients. Proton therapy was more likely to be cost-effective for patients with p16-positive tumors ($234,201/QALY), compared to p16-negative tumors ($516,297/QALY). For patients with p16-positive tumors treated with comprehensive nodal irradiation, proton therapy is estimated to be cost-effective in ≥ 50% of sampled cases for 8/9 patients at $500,000/QALY, compared to 6/24 patients who either have p16-negative tumors or receive unilateral neck irradiation.

Conclusions: Proton therapy cost-effectiveness varies greatly among oropharyngeal cancer patients, and highlights the importance of individualized decision-making. Although the upfront cost, societal willingness to pay and healthcare administration can vary greatly among different countries, identifying patients for whom proton therapy will have the greatest benefit can optimize resource allocation and inform prospective clinical trial design.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13014-021-01745-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7819210PMC
January 2021

Simulation of spread-out bragg peaks in proton beams using Geant4/TOPAS.

Biomed Phys Eng Express 2020 05 14;6(4):047001. Epub 2020 May 14.

Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, 10467, United States of America.

The simulation of proton Spread-Out Bragg Peaks (SOBPs) was implemented using the Geant4-based TOPAS Monte Carlo software. Dynamic proton energy switching was implemented using TOPAS time features, while beam weights were calculated using an empirical power law formalism with Bragg peaks spaced by 0.5 mm. To find power parameters yielding flat SOBPs we sampled power parameters for maximum kinetic energies of 50 MeV to 250 MeV and SOBP widths of 15% to 40% of the depth of the distal SOBP end. Simulations were run in a 50 cm cubic water phantom using a uniform squared proton beam. Depth dose was scored along the central axis in a binned cylinder with 1 cm diameter in 2.5 mm increments. Power parameters yielding a flat SOBPs were found to vary with, both energy and SOBP width and differed significantly from previously reported values based on simulations with MCNPX.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/2057-1976/ab8f6dDOI Listing
May 2020

Stereotactic Radiosurgery for Vestibular Schwannomas: Tumor Control Probability Analyses and Recommended Reporting Standards.

Int J Radiat Oncol Biol Phys 2020 Dec 26. Epub 2020 Dec 26.

Machine Learning Department, Moffitt Cancer Center, Tampa, Florida.

Purpose: We sought to investigate the tumor control probability (TCP) of vestibular schwannomas after single-fraction stereotactic radiosurgery (SRS) or hypofractionated SRS over 2 to 5 fractions (fSRS).

Methods And Materials: Studies (PubMed indexed from 1993-2017) were eligible for data extraction if they contained dosimetric details of SRS/fSRS correlated with local tumor control. The rate of tumor control at 5 years (or at 3 years if 5-year data were not available) were collated. Poisson modeling estimated the TCP per equivalent dose in 2 Gy per fraction (EQD2) and in 1, 3, and 5 fractions.

Results: Data were extracted from 35 publications containing a total of 5162 patients. TCP modeling was limited by the absence of analyzable data of <11 Gy in a single-fraction, variability in definition of "tumor control," and by lack of significant increase in TCP for doses >12 Gy. Using linear-quadratic-based dose conversion, the 3- to 5-year TCP was estimated at 95% at an EQD2 of 25 Gy, corresponding to 1-, 3-, and 5-fraction doses of 13.8 Gy, 19.2 Gy, and 21.5 Gy, respectively. Single-fraction doses of 10 Gy, 11 Gy, 12 Gy, and 13 Gy predicted a TCP of 85.0%, 88.4%, 91.2%, and 93.5%, respectively. For fSRS, 18 Gy in 3 fractions (EQD2 of 23.0 Gy) and 25 Gy in 5 fractions (EQD2 of 30.2 Gy) corresponded to TCP of 93.6% and 97.2%. Overall, the quality of dosimetric reporting was poor; recommended reporting guidelines are presented.

Conclusions: With current typical SRS doses of 12 Gy in 1 fraction, 18 Gy in 3 fractions, and 25 Gy in 5 fractions, 3- to 5-year TCP exceeds 91%. To improve pooled data analyses to optimize treatment outcomes for patients with vestibular schwannoma, future reports of SRS should include complete dosimetric details with well-defined tumor control and toxicity endpoints.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2020.11.019DOI Listing
December 2020

Validating the SumMean F-FDG PET Textural Feature as a Prognostic Marker in an Independent Cohort of Locally Advanced Non-Small Cell Lung Cancer Patients Undergoing Concurrent Chemoradiation Therapy.

Pract Radiat Oncol 2021 Jan-Feb;11(1):e46-e51. Epub 2020 Oct 19.

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, New York; Department of Radiation Oncology, Montefiore Medical Center, Bronx, New York.

Purpose: Analyses from the ACRIN6668/RTOG0235 trial data identified the SumMean textural feature, calculated from 18-fluorodeoxyglucose positron emission tomography for tumors with a metabolic tumor volume >93 cm, as a predictor of overall survival (OS) for patients with locally advanced non-small cell lung cancer (LA-NSCLC) receiving concurrent chemoradiation therapy. Here, we validated that finding in a completely independent patient cohort from a single institution.

Methods And Materials: We identified patients with LA-NSCLC who underwent staging 18-fluorodeoxyglucose positron emission tomography and received definitive chemoradiation therapy at our institution between 2007 and 2018. Primary tumors were segmented semiautomatically, and SumMean score was calculated for each tumor and categorized according to the previously proposed cutoff of 0.018. In patients with metabolic tumor volume >93 cm, SumMean was evaluated as a predictor of progression-free survival (PFS) and OS using log rank and Cox proportional hazards testing.

Results: One hundred forty-eight patients met inclusion criteria, and 34 had large tumors (>93 cm). Twelve (35%) had high SumMean, and 22 (65%) had low SumMean. SumMean was not significantly associated with other clinical variables. Median PFS for patients with large tumors and low SumMean was 5.8 months, compared with 41.1 months for patients with large tumors and high SumMean (log rank P = .022). Median OS for patients with large tumors and low SumMean was 15.0 months; median OS was not reached for patients with large tumors and high SumMean (log rank P = .014). In multivariable analysis, high SumMean was an independent predictor of improved OS (hazard ratio, 0.26; 95% confidence interval, 0.07-0.94; P = .041) and PFS (hazard ratio, 0.30; 95% confidence interval, 0.10-0.86; P = .026).

Conclusions: We externally validated SumMean as a prognostic marker for patients with LA-NSCLC treated with chemoradiation therapy in an independent patient cohort. Future studies will explore potential mechanisms for this association and how textural features may help guide treatment decisions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prro.2020.10.004DOI Listing
October 2020

Outcomes From Whole-Brain Reirradiation Using Pulsed Reduced Dose Rate Radiation Therapy.

Adv Radiat Oncol 2020 Sep-Oct;5(5):834-839. Epub 2020 Jul 8.

Department of Human Oncology, University of Wisconsin School of Medicine and Public Health, Carbone Cancer Center, Madison, Wisconsin.

Purpose: Recurrent intracranial metastases after whole-brain irradiation pose a clinical challenge owing to the escalating morbidity associated with their treatment. Although stereotactic radiosurgery is increasingly being used, there are still situations in which whole-brain reirradiation (ReRT) continues to be appropriate. Here, we report our experience using whole-brain pulsed reduced dose rate radiation therapy (PRDR), a method that delivers radiation at a slower rate of 0.067 Gy/min to potentially increase sublethal damage repair and decrease toxicity.

Methods And Materials: Patients undergoing whole-brain ReRT with PRDR from January 1, 2001 to March 2019 were analyzed. The median PRDR ReRT dose was 26 Gy in 2 Gy fractions, resulting in a median total whole-brain dose of 59.5 Gy. Cox regression analysis was used for multivariate analysis. The Kaplan-Meier method was used for overall survival, progression free survival, and to evaluate the ReRT score. Binary logistic regression was employed to evaluate variables associated with rapid death.

Results: Seventy-five patients were treated with whole-brain PRDR radiation therapy. The median age was 54 (range, 26-72), the median Karnofsky performance status (KPS) was 80, and 86.7% had recursive partitioning analysis scores of 2. Thirty-two patients had over 10 metastases and 11 had leptomeningeal disease. The median overall survival was 4.1 months (range, 0.29-59.5 months) with a 1 year overall survival of 10.4%. Age, KPS, dexamethasone usage, and intracranial disease volume were significantly correlated with overall survival on multivariate analysis. A KPS ≤70 was associated with rapid death after radiation. The prognostic value of the ReRT score was validated. The most common acute toxicities were fatigue (23.1%) and headache (16.9%).

Conclusions: In this large cohort of patients with advanced intracranial metastases, PRDR achieves acceptable survival and may decrease toxicity associated with ReRT. PRDR is an easily implemented technique and is a viable treatment option for ReRT of brain metastases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.adro.2020.06.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7557211PMC
July 2020

Reply to Chowdhary et al.

Adv Radiat Oncol 2020 Jul-Aug;5(4):713-714. Epub 2020 Aug 3.

Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.adro.2020.06.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397987PMC
August 2020

Extent of Prior Lung Irradiation and Mortality in COVID-19 Patients With a Cancer History.

Adv Radiat Oncol 2020 Jul-Aug;5(4):707-710. Epub 2020 May 20.

Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York.

Purpose: There have been nearly 200,000 deaths worldwide so far from coronavirus disease 2019 (COVID-19), which is caused by a coronavirus called SARS-CoV-2. Cancer history appears to be a poor prognostic factor for COVID-19 patients, although the reasons for this are unclear. In this report, we assess whether extent of prior lung irradiation is a risk factor for death as a result of COVID-19 infection.

Methods And Materials: Patients who tested positive for COVID-19 between March 14 and April 15, 2020, at our institution and who previously received radiation therapy for cancer in our department were included in this analysis. Patient characteristics and metrics describing the extent of lung irradiation were tabulated. Cox regression models were used to identify predictors of death after COVID-19 diagnosis. A logistic model was used to characterize the association between mean lung radiation therapy dose and 14-day mortality risk after COVID-19 diagnosis.

Results: For the study, 107 patients met the inclusion criteria. With a median follow-up of 7 days from COVID-19 diagnosis for surviving patients, 24 deaths have been observed. The actuarial survival rate 14 days after COVID-19 testing is 66%. Increasing mean lung dose (hazard ratio [HR] per Gy = 1.1, = .002), lung cancer diagnosis (HR = 3.0, = .034), and receiving radiation therapy between 1 month and 1 year before COVID-19 testing (HR = 3.4, = .013) were associated with increased risk of death. Our survival model demonstrates a near linear relationship between mortality risk after COVID-19 diagnosis and mean lung radiation therapy dose.

Conclusions: COVID-19 patients with a history of radiation therapy for cancer have a poor prognosis, and mortality risk appears to be associated with extent of lung irradiation. Validation of these findings will be critical as the COVID-19 pandemic continues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.adro.2020.04.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239013PMC
May 2020

COVID-19 Incidentally Detected on PET/CT During Work-up for Locally Advanced Head and Neck Cancer.

In Vivo 2020 Jun;34(3 Suppl):1681-1684

Department of Radiation Oncology, Montefiore Medical Center, New York, NY, U.S.A.

Aim: To describe the incidental detection of COVID-19 disease on positron-emission tomography/computed tomography (PET/CT) in a patient with cancer despite initial negative swab by polymerase chain reaction (PCR).

Case Report: Clinical and radiographic data were obtained from the electronic medical record. Nasopharyngeal swabs were obtained and evaluated for COVID-19 by the Food and Drug Administration-approved reverse transcription-PCR assays. On radiographic examination, PET/CT was consistent with COVID-19-related pneumonia not seen on prior imaging. Initial nasopharyngeal swab 2 days after PET/CT imaging was negative for COVID-19. Subsequent repeat swab 10 days later was positive for COVID-19, while the patient was febrile on screening assessment. The patient remained COVID-19-positive until 1 month after abnormal PET/CT imaging.

Conclusion: PET/CT can be sensitive for early COVID-19 detection, even in the setting of a negative confirmatory PCR test. This highlights the importance of continued patient surveillance and use of appropriate personal protective equipment to minimize COVID-19 transmission.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.21873/invivo.11961DOI Listing
June 2020

Recommendations of megavoltage computed tomography settings for the implementation of adaptive radiotherapy on helical tomotherapy units.

J Appl Clin Med Phys 2020 May 26;21(5):87-92. Epub 2020 Mar 26.

Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, USA.

Megavoltage computed tomography (MVCT) image quality metrics were evaluated on an Accuray Radixact unit to recommend scan settings for the implementation of a consistent adaptive radiotherapy program. Megavoltage computed tomography image quality was evaluated and compared to a kilovoltage CT (kVCT) simulator using a commercial cone beam computed tomography image quality phantom. Megavoltage computed tomographies were acquired on the Accuray Radixact using fine, normal, and coarse pitches, with all available reconstruction slice thicknesses, each of which were reconstructed using standard and iterative reconstruction (IR). Image quality metrics (IQM) were evaluated using DoseLab: automatically and manually calculated spatial resolution, subject contrast, and contrast-to-noise ratio (CNR). Scanning time was 15.6 s/cm for fine, 8.1 s/cm for normal, and 5.6 s/cm for coarse pitch. Automatically evaluated spatial resolutions ranged from 0.39, 0.41, to 0.42 lp/mm for standard reconstruction and from 0.24, 0.21, to 0.18 lp/mm for soft-tissue IR, respectively, with general IR yielding values in between these. Spatial resolution for kVCT was measured to be at least 0.42 lp/mm. Contrast was consistent across MVCT settings with 8.1 ± 0.2%, while kVCT contrast was 10.27 ± 0.05%. CNR was calculated to be 3.3 ± 0.4 for standard reconstruction, 7.4 ± 0.4 for general IR, and 12.0 ± 1.9 for soft-tissue IR. It was found that increasing reconstruction slice thickness for a given pitch does not improve IQMs. Based on the consistency of contrast metrics across pitch values and the only slightly reduced spatial resolution using normal compared to fine pitch, we recommend the use of normal pitch with 2 mm slice thickness to maximize image quality for ART while limiting scanning time. Only for sites for which improved CNR is required and reduced spatial resolution is acceptable, soft-tissue IR is recommended.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/acm2.12859DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7286013PMC
May 2020

Hippocampal Avoidance During Whole-Brain Radiotherapy Plus Memantine for Patients With Brain Metastases: Phase III Trial NRG Oncology CC001.

J Clin Oncol 2020 04 14;38(10):1019-1029. Epub 2020 Feb 14.

Vanderbilt University Medical Center, Ingram Cancer Center, Nashville, TN.

Purpose: Radiation dose to the neuroregenerative zone of the hippocampus has been found to be associated with cognitive toxicity. Hippocampal avoidance (HA) using intensity-modulated radiotherapy during whole-brain radiotherapy (WBRT) is hypothesized to preserve cognition.

Methods: This phase III trial enrolled adult patients with brain metastases to HA-WBRT plus memantine or WBRT plus memantine. The primary end point was time to cognitive function failure, defined as decline using the reliable change index on at least one of the cognitive tests. Secondary end points included overall survival (OS), intracranial progression-free survival (PFS), toxicity, and patient-reported symptom burden.

Results: Between July 2015 and March 2018, 518 patients were randomly assigned. Median follow-up for alive patients was 7.9 months. Risk of cognitive failure was significantly lower after HA-WBRT plus memantine versus WBRT plus memantine (adjusted hazard ratio, 0.74; 95% CI, 0.58 to 0.95; = .02). This difference was attributable to less deterioration in executive function at 4 months (23.3% 40.4%; = .01) and learning and memory at 6 months (11.5% 24.7% [ = .049] and 16.4% 33.3% [ = .02], respectively). Treatment arms did not differ significantly in OS, intracranial PFS, or toxicity. At 6 months, using all data, patients who received HA-WBRT plus memantine reported less fatigue ( = .04), less difficulty with remembering things ( = .01), and less difficulty with speaking ( = .049) and using imputed data, less interference of neurologic symptoms in daily activities ( = .008) and fewer cognitive symptoms ( = .01).

Conclusion: HA-WBRT plus memantine better preserves cognitive function and patient-reported symptoms, with no difference in intracranial PFS and OS, and should be considered a standard of care for patients with good performance status who plan to receive WBRT for brain metastases with no metastases in the HA region.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1200/JCO.19.02767DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7106984PMC
April 2020

A technique to generate synthetic CT from MRI for abdominal radiotherapy.

J Appl Clin Med Phys 2020 Feb 11;21(2):136-143. Epub 2020 Feb 11.

Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, USA.

Purpose: To investigate a method to classify tissues types for synthetic CT generation using MRI for treatment planning in abdominal radiotherapy.

Methods: An institutional review board approved volunteer study was performed on a 3T MRI scanner. In-phase, fat and water images were acquired for five volunteers with breath-hold using an mDixon pulse sequence. A method to classify different tissue types for synthetic CT generation in the abdomen was developed. Three tissue clusters (fat, high-density tissue, and spine/air/lungs) were generated using a fuzzy-c means clustering algorithm. The third cluster was further segmented into three sub-clusters that represented spine, air, and lungs. Therefore, five segments were automatically generated. To evaluate segmentation accuracy using the method, the five segments were manually contoured on MRI images as the ground truth, and the volume ratio, Dice coefficient, and Hausdorff distance metric were calculated. The dosimetric effect of segmentation accuracy was evaluated on simulated targets close to air, lungs, and spine using a two-arc volumetric modulated arc therapy (VMAT) technique.

Results: The volume ratio of auto-segmentation to manual segmentation was 0.88-2.1 for the air segment and 0.72-1.13 for the remaining segments. The range of the Dice coefficient was 0.24-0.83, 0.84-0.93, 0.94-0.98, 0.93-0.96, and 0.76-0.79 for air, fat, lungs, high-density tissue, and spine, respectively. The range of the mean Hausdorff distance was 3-29.1 mm, 0.5-1.3 mm, 0.4-1 mm, 0.7-1.6 mm, and 1.2-1.4 mm for air, fat, lungs, high-density tissue, and spine, respectively. Despite worse segmentation accuracy in air and spine, the dosimetric effect was 0.2% ± 0.2%, with a maximum difference of 0.8% for all target locations.

Conclusion: A method to generate synthetic CT in the abdomen was developed, and segmentation accuracy and its dosimetric effect were evaluated. Our results demonstrate the potential of using MRI alone for treatment planning in the abdomen.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/acm2.12816DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7020981PMC
February 2020

In Reply to Klement et al.

Int J Radiat Oncol Biol Phys 2019 Nov 15. Epub 2019 Nov 15.

Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2018.02.013DOI Listing
November 2019

F-Fluorodeoxyglucose PET in Locally Advanced Non-small Cell Lung Cancer: From Predicting Outcomes to Guiding Therapy.

PET Clin 2020 Jan;15(1):55-63

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY 10461, USA.

PET using 18-fluorodeoxyglucose (FDG) has become an important part of the work-up for non-small cell lung cancer (NSCLC). This article summarizes advancements in using FDG-PET for patients with locally advanced NSCLC treated with definitive radiation therapy (RT). This article discusses prognostication of outcome based on pretreatment or midtreatment PET metrics, using textural image features to predict treatment outcomes, and using PET to define RT target volumes and inform RT dose modifications. The role of PET is evolving and is moving toward using quantitative image information, with the overarching goal of individualizing therapy to improve outcomes for patients with NSCLC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cpet.2019.08.009DOI Listing
January 2020

Non-Invasive Targeted Hepatic Irradiation and SPECT/CT Functional Imaging to Study Radiation-Induced Liver Damage in Small Animal Models.

Cancers (Basel) 2019 Nov 15;11(11). Epub 2019 Nov 15.

Department of Radiation Oncology, Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

Radiation therapy (RT) has traditionally not been widely used in the management of hepatic malignancies for fear of toxicity in the form of radiation-induced liver disease (RILD). Pre-clinical hepatic irradiation models can provide clinicians with better understanding of the radiation tolerance of the liver, which in turn may lead to the development of more effective cancer treatments. Previous models of hepatic irradiation are limited by either invasive laparotomy procedures, or the need to irradiate the whole or large parts of the liver using external skin markers. In the setting of modern-day radiation oncology, a truly translational animal model would require the ability to deliver RT to specific parts of the liver, through non-invasive image guidance methods. To this end, we developed a targeted hepatic irradiation model on the Small Animal Radiation Research Platform (SARRP) using contrast-enhanced cone-beam computed tomography image guidance. Using this model, we showed evidence of the early development of region-specific RILD through functional single photon emission computed tomography (SPECT) imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/cancers11111796DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896151PMC
November 2019

Two-dimensional solid-state array detectors: A technique for in vivo dose verification in a variable effective area.

J Appl Clin Med Phys 2019 Nov 14;20(11):88-94. Epub 2019 Oct 14.

Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW, Australia.

Purpose: We introduce a technique that employs a 2D detector in transmission mode (TM) to verify dose maps at a depth of d in Solid Water. TM measurements, when taken at a different surface-to-detector distance (SDD), allow for the area at d (in which the dose map is calculated) to be adjusted.

Methods: We considered the detector prototype "MP512" (an array of 512 diode-sensitive volumes, 2 mm spatial resolution). Measurements in transmission mode were taken at SDDs in the range from 0.3 to 24 cm. Dose mode (DM) measurements were made at d in Solid Water. We considered radiation fields in the range from 2 × 2 cm to 10 × 10 cm , produced by 6 MV flattened photon beams; we derived a relationship between DM and TM measurements as a function of SDD and field size. The relationship was used to calculate, from TM measurements at 4 and 24 cm SDD, dose maps at d in fields of 1 × 1 cm and 4 × 4 cm , and in IMRT fields. Calculations were cross-checked (gamma analysis) with the treatment planning system and with measurements (MP512, films, ionization chamber).

Results: In the square fields, calculations agreed with measurements to within ±2.36%. In the IMRT fields, using acceptance criteria of 3%/3 mm, 2%/2 mm, 1%/1 mm, calculations had respective gamma passing rates greater than 96.89%, 90.50%, 62.20% (for a 4 cm SSD); and greater than 97.22%, 93.80%, 59.00% (for a 24 cm SSD). Lower rates (1%/1 mm criterion) can be explained by submillimeter misalignments, dose averaging in calculations, noise artifacts in film dosimetry.

Conclusions: It is possible to perform TM measurements at the SSD which produces the best fit between the area at d in which the dose map is calculated and the size of the monitored target.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/acm2.12744DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839376PMC
November 2019

Spinal Cord Dose Tolerance to Stereotactic Body Radiation Therapy.

Int J Radiat Oncol Biol Phys 2019 Oct 10. Epub 2019 Oct 10.

Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.

Spinal cord tolerance data for stereotactic body radiation therapy (SBRT) were extracted from published reports, reviewed, and modelled. For de novo SBRT delivered in 1 to 5 fractions, the following spinal cord point maximum doses (D) are estimated to be associated with a 1% to 5% risk of radiation myelopathy (RM): 12.4 to 14.0 Gy in 1 fraction, 17.0 Gy in 2 fractions, 20.3 Gy in 3 fractions, 23.0 Gy in 4 fractions, and 25.3 Gy in 5 fractions. For reirradiation SBRT delivered in 1 to 5 fractions, reported factors associated with a lower risk of RM include cumulative thecal sac equivalent dose in 2 Gy fractions with an alpha/beta of 2 (EQD2) D ≤70 Gy; SBRT thecal sac EQD2 D ≤25 Gy, thecal sac SBRT EQD2 D to cumulative EQD2 D ratio ≤0.5, and a minimum time interval to reirradiation of ≥5 months. Larger studies containing complete institutional cohorts with dosimetric data of patients treated with spine SBRT, with and without RM, are required to refine RM risk estimates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2019.09.038DOI Listing
October 2019

A skin dose prediction model based on in vivo dosimetry and ultrasound skin bridge measurements during intraoperative breast radiation therapy.

Brachytherapy 2019 Sep - Oct;18(5):720-726. Epub 2019 Jun 20.

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY; Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY; Department of Neurology, Albert Einstein College of Medicine, Bronx, NY. Electronic address:

Purpose: Using in vivo measurements from optically stimulated luminescence dosimeters (OSLDs) to develop and validate a prediction model for estimating the skin dose received by patients undergoing breast intraoperative radiation therapy (IORT).

Methods And Materials: IORT was performed using INTRABEAM-600 with spherical applicators placed in the lumpectomy cavity. Ultrasound skin bridge measurements were used to determine the applicator-to-skin distance, with OSLDs placed to measure the skin surface dose at the corresponding points. The OSLD response was calibrated for the 50 kVp INTRABEAM-600 output. Models were fit to describe the dose fall-off with increasing applicator-to-skin distance and the best fitting model was chosen for estimating skin dose.

Results: Twenty four patients with 25 lumpectomy cavities were included, and the average skin dose recorded was 1.18 Gy ± 0.88 Gy, ranging from 0.17 Gy to 4.77 Gy, with an average applicator-to-skin distance of 19.9 mm ± 5.1 mm. An exponential-plateau model was found to best describe the dose fall-off with a root-mean-square error of 0.73. This model was then validated prospectively using skin dose measurements from five consecutive patients. Validation measurements were well within the 95% prediction limits of the model, with a root-mean-square error of 0.52, showing that the prediction model accurately estimates skin dose using ultrasound skin bridge measurements.

Conclusions: This prediction model constitutes a useful tool for estimating the skin dose received during breast lumpectomy IORT. The model and accompanying 95% confidence intervals can be used to establish a minimum allowable skin bridge distance, effectively limiting the maximum allowable skin dose.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.brachy.2019.05.012DOI Listing
March 2020

Determining efficient helical IMRT modulation factor from the MLC leaf-open time distribution on precision treatment planning system.

J Appl Clin Med Phys 2019 May 8;20(5):64-74. Epub 2019 Apr 8.

Department of Radiation Oncology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA.

Purpose: Since the modulation factor (MF) impacts both plan quality and delivery efficiency in tomotherapy Intensity Modulated Radiation Therapy (IMRT) treatment planning, the purpose of this study was to demonstrate a technique in determining an efficient MF from the Multileaf Collimator (MLC) leaf-open time (LOT) distribution of a tomotherapy treatment delivery plan.

Methods: Eight clinical plans of varying complexity were optimized with the highest allowed MF on the Accuracy Precision treatment planning system. Using a central limit theorem argument a range of reduced MFs were then determined from the first two moments of the LOT distribution. A step down approach was used to calculate the reduced-MF plans and plan comparison tools available on the Precision treatment planning system were used to evaluate dose differences with the reference plan.

Results: A reduced-MF plan that balanced delivery time and dosimetric quality was found from the set of five MFs determined from the LOT distribution of the reference plan. The reduced-MF plan showed good agreement with the reference plan (target and critical organ dose-volume region of interest dose differences were within 1% and 2% of prescription dose, respectively).

Discussion: Plan evaluation and acceptance criteria can vary depending on individual clinical expectations and dosimetric quality trade-offs. With the scheme presented in this paper a planner should be able to efficiently generate a high-quality plan with efficient delivery time without knowing a good MF beforehand.

Conclusion: A methodology for deriving a reduced MF from the LOT distribution of a high MF treatment plan using the central limit theorem has been presented. A scheme for finding a reduced MF from a set of MFs that results in a plan balanced in both dosimetric quality and treatment delivery efficiency has also been presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/acm2.12581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6523016PMC
May 2019

Local Control After Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer.

Int J Radiat Oncol Biol Phys 2019 Apr 5. Epub 2019 Apr 5.

Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.

Purpose: Numerous dose and fractionation schedules have been used to treat medically inoperable stage I non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) or stereotactic ablative radiation therapy. We evaluated published experiences with SBRT to determine local control (LC) rates as a function of SBRT dose.

Methods And Materials: One hundred sixty published articles reporting LC rates after SBRT for stage I NSCLC were identified. Quality of the series was assessed by evaluating the number of patients in the study, homogeneity of the dose regimen, length of follow-up time, and reporting of LC. Clinical data including 1, 2, 3, and 5-year tumor control probabilities for stages T1, T2, and combined T1 and T2 as a function of the biological effective dose were fitted to the linear quadratic, universal survival curve, and regrowth models.

Results: Forty-six studies met inclusion criteria. As measured by the goodness of fit χ/ndf, with ndf as the number of degrees of freedom, none of the models were ideal fits for the data. Of the 3 models, the regrowth model provides the best fit to the clinical data. For the regrowth model, the fitting yielded an α-to-β ratio of approximately 25 Gy for T1 tumors, 19 Gy for T2 tumors, and 21 Gy for T1 and T2 combined. To achieve the maximal LC rate, the predicted physical dose schemes when prescribed at the periphery of the planning target volume are 43 ± 1 Gy in 3 fractions, 47 ± 1 Gy in 4 fractions, and 50 ± 1 Gy in 5 fractions for combined T1 and T2 tumors.

Conclusions: Early-stage NSCLC is radioresponsive when treated with SBRT or stereotactic ablative radiation therapy. A steep dose-response relationship exists with high rates of durable LC when physical doses of 43-50 Gy are delivered in 3 to 5 fractions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2019.03.045DOI Listing
April 2019

Origin of Locoregional Recurrences After Definitive Intensity-modulated Radiation Therapy (IMRT) for Laryngeal Cancer Determined Based on Follow-up PET/CT Imaging.

Cureus 2019 Jan 8;11(1):e3856. Epub 2019 Jan 8.

Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA.

Purpose: The aim of our study was to report on patterns of failure using detailed information from follow-up positron emission tomography-computed tomography (PET/CT) scans for patients with laryngeal squamous cell carcinoma (SCCA) treated with definitive radiation therapy using intensity-modulated radiation therapy (IMRT).

Methods: One hundred and sixty-eight patients with laryngeal SCCA treated with definitive IMRT using a simultaneous integrated boost were included. The point of recurrence origin on follow-up PET/CT was determined using two separate data-driven methods. The first method, the mathematical epicenter point of origin (PO), calculated the mathematical focal epicenter point for which the maximum distance to the surface of the surrounding volume was smaller than for any other point. The second method, maximum standardized uptake value point of origin (PO), calculated the voxel with maximum standardized uptake value (SUV) uptake within the recurrence volume. The failure pattern was then determined by whether the point of recurrence origin fell within the low, intermediate, or high-risk target volumes in the original treatment planning CT.

Results: Thirty-five primary/nodal recurrences in 33 patients were included in the analysis. In the PO method, 94% (33/35) of all recurrences originated either within the high-risk gross tumor volume (GTV) or within an average of 0.9 ± 1.3 mm from it. In the PO method, 91% (32/35) of all recurrences originated either within the GTV or within an average of 1.8 ± 1.7 mm from it. There were no recurrences outside the low-risk planning target volume (PTV) for the PO method but there was one for the PO method, which was 19.8 mm away from the edge of the gross tumor volume receiving 70 Gy (GTV). Increasing distance between the two different origin points was strongly correlated with the size of the recurrence volume.

Conclusion: The majority of recurrences for laryngeal cancer patients treated with definitive IMRT originated from within the high-dose treatment region. This can have implications for reducing clinical target volumes while using a risk-adaptive treatment approach to both constrain dose to critical areas and further escalate the dose to the gross tumor to improve locoregional control rates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7759/cureus.3856DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6420324PMC
January 2019

Interstitial Surgical Cavity Sizing Applicators for the Treatment of the Breast Lumpectomy Cavity with Intraoperative Radiation Therapy.

Cureus 2018 Dec 5;10(12):e3693. Epub 2018 Dec 5.

Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA.

Surgical cavity sizing applicators were developed for utilization prior to intraoperative radiation therapy (IORT) of the breast lumpectomy cavity with the Zeiss INTRABEAM (Carl Zeiss Meditec AG, Jena, Germany) device. The use of these applicators minimizes the number of sterilizations of the treatment applicator, which is currently limited to 100 sterilizations per applicator. This maximizes the number of patients who can be treated with each applicator, resulting in cost savings for the treating institution.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7759/cureus.3693DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390889PMC
December 2018

Immunomodulatory Effects of Stereotactic Body Radiation Therapy: Preclinical Insights and Clinical Opportunities.

Int J Radiat Oncol Biol Phys 2019 Mar 2. Epub 2019 Mar 2.

Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2019.02.046DOI Listing
March 2019

A Quantitative Clinical Decision-Support Strategy Identifying Which Patients With Oropharyngeal Head and Neck Cancer May Benefit the Most From Proton Radiation Therapy.

Int J Radiat Oncol Biol Phys 2019 07 26;104(3):540-552. Epub 2018 Nov 26.

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, New York; Department of Radiation Oncology, Montefiore Medical Center, Bronx, New York; Department of Neurology, Albert Einstein College of Medicine, Bronx, New York. Electronic address:

Purpose: Developing a quantitative decision-support strategy estimating the impact of normal tissue complications from definitive radiation therapy (RT) for head and neck cancer (HNC). We developed this strategy to identify patients with oropharyngeal HNC who may benefit most from receiving proton RT.

Methods And Materials: Recent normal tissue complication probability (NTCP) models for dysphagia, esophagitis, hypothyroidism, xerostomia, and oral mucositis were used to estimate NTCP for 33 patients with oropharyngeal HNC previously treated with photon intensity modulated radiation therapy (IMRT). Comparative proton therapy plans were generated using clinical protocols for HNC RT at a collaborating proton center. Organ-at-risk (OAR) doses from photon and proton RT plans were used to calculate NTCPs; Monte Carlo sampling 10,000 times was used for each patient to account for model parameter uncertainty. The latency and duration of each complication were modeled from calculated NTCP, accounting for age-, sex-, smoking- and p16-specific conditional survival probability. Complications were then assigned quality-adjustment factors based on severity to calculate quality-adjusted life years (QALYs) lost from each complication.

Results: Based on our institutional-delivered photon IMRT doses and the achievable proton therapy doses, the average QALY reduction from all HNC RT complications for photon and proton therapy was 1.52 QALYs versus 1.15 QALYs, with proton therapy sparing 0.37 QALYs on average (composite 95% confidence interval, 0.27-2.53 QALYs). Long-term complications (dysphagia and xerostomia) contributed most to the QALY reduction. The QALYs spared with proton RT varied considerably among patients, ranging from 0.06 to 0.84 QALYs. Younger patients with p16-positive tumors who smoked ≤10 pack-years may benefit most from proton therapy, although this finding should be validated using larger patient series. A sensitivity analysis reducing photon IMRT doses to all OARs by 20% resulted in no overall estimated benefit with proton therapy with -0.02 QALYs spared, although some patients still had an estimated benefit in this scenario, ranging from -0.50 to 0.43 QALYs spared.

Conclusions: This quantitative decision-support strategy allowed us to identify patients with oropharyngeal cancer who might benefit the most from proton RT, although the estimated benefit of proton therapy ultimately depends on the OAR doses achievable with modern photon IMRT solutions. These results can help radiation oncologists and proton therapy centers optimize resource allocation and improve quality of life for patients with HNC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2018.11.039DOI Listing
July 2019

Revisiting the dose constraints for head and neck OARs in the current era of IMRT.

Oral Oncol 2018 11 8;86:8-18. Epub 2018 Sep 8.

Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY 10461, USA; Department of Neurology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Electronic address:

Head and neck cancer poses a particular challenge in radiation therapy, whilst being an effective treatment modality it requires very high doses of radiation to provide effective therapy. This is further complicated by the fact that the head and neck region contains a large number of radiosensitive tissues, often resulting in patients experiencing debilitating normal tissue complications. In the era of intensity-modulated radiation therapy (IMRT) treatments can be delivered using non-uniform dose distributions selectively aimed at reducing the dose to critical organs-at-risk while still adequately covering the tumor target. Dose-volume constraints for the different risk organs play a vital role in one's ability to devise the best IMRT treatment plan for a head and neck cancer patient. To this end, it is pivotal to have access to the latest and most relevant dose constraints available and as such the goal of this review is to provide a summary of suggested dose-volume constraints for head and neck cancer RT that have been published after the QUANTEC reports were made available in early 2010.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.oraloncology.2018.08.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6481934PMC
November 2018

Trends in Physics Contributions to the 'Red Journal': A 30-year Journey and Comparison to Global Trends.

Cureus 2018 Jul 20;10(7):e3012. Epub 2018 Jul 20.

Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA.

Introduction: In this study, we catalogued physics contributions in the Red Journal over the past three decades and compared publication trends with global publication trends.

Methods: We used the website of the Red Journal (International Journal of Radiation Oncology, Biology, and Physics) to access physics contributions published between 1988 and 2017. The contributions were catalogued following taxonomy guidelines endorsed by the American Association of Physicists in Medicine. From each issue, publications classified as "Physics Contributions" or as "Technical Innovations" or listed a physicist as one of the primary authors was indexed. Results are presented using descriptive statistics; chi-square [Formula: see text] testing were utilized to examine trends in contributions over 10-year time intervals. For global trend comparison of Red Journal physics contributions, we utilized PubMed database to obtain publication counts on the topics of interest.

Results: A total of 2,852 physics contributions were indexed (86 volumes and 436 issues). Overall, 76% of contributions were photon-beam therapy applications, 15% brachytherapy, 7% particle-beam therapy, and 3% electron-beam therapy. [Formula: see text] analyses revealed significant changes in this distribution over time (p<0.001). Brachytherapy accounted for 23% of publications in the first decade, compared to 7% in the third decade. Particle beam therapy accounted for 4% of publications in the first decade and 12% in the third decade. Among treatment techniques, three-dimensional conformal radiation therapy (3D-CRT) accounted for 64% of contributions in the first decade, compared to 3% in the third decade. Intensity-modulated radiation therapy (IMRT)/volumetric modulated arc therapy (VMAT) accounted for 4% in the first decade, compared to 54% in the third decade. Significant increases in the proportions of studies focused on motion management, functional imaging for treatment planning, and radiation safety/quality assurance during the third decade were observed (p<0.001).

Conclusion: Trends of physics publications in the Red Journal and globally, in general, largely mirror technological advances in the field of radiation oncology. These changes reflect a technological transition in the field over three decades from beam's-eye-view designed static treatment ports to functional imaging and knowledge-based treatment planning with biological dose optimization and real-time tumor tracking.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7759/cureus.3012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6150769PMC
July 2018

Towards abdominal MRI-based treatment planning using population-based Hounsfield units for bulk density assignment.

Phys Med Biol 2018 07 24;63(15):155003. Epub 2018 Jul 24.

Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, United States of America. Albert Einstein College of Medicine, Bronx, NY, United States of America.

This study investigates the dosimetric impact of using population-based Hounsfield units (HUs) and ICRU-based HUs as a function of the number of tissue segments for bulk density assignment toward MRI-based treatment planning in the abdomen. To avoid potential geometric differences between CT and MR images, CT images rather than MR images were chosen to simulate an MRI-only planning scenario. A retrospective study was performed utilizing 18 patients that had previously undergone stereotactic body radiation therapy for liver or pancreas cancer. HU values in the CT datasets were collected for various tissue types, and compared with the HUs derived from ICRU report 46. Doses were recalculated using the fluence obtained from clinical plans and with (1) homogeneous assignment, (2) ICRU-based HU assignment and (3) population-based HU assignment using three, four, five, nine or ten tissue segments. Dose-volume metrics for targets and organs-at-risk for all scenarios were compared with those obtained using the clinical CT. For the planning target volume (PTV) D99.9%, the mean differences from clinical CT plans were  -2.1%  ±  3.9%, -0.6%  ±  0.3% and  -0.1%  ±  0.3% for homogeneity, ICRU-HUs and population-HUs using ten tissue segments, respectively. The population-HU method resulted in better dosimetric accuracy compared to the ICRU-HU method (p-value  <  0.05). The dosimetric accuracy of homogeneity plans was comparable to that of both ICRU-HU and population-HU plans when targets were far from the lungs but deteriorated when targets were close to the lungs. As the number of tissue segments decreased, the dosimetric accuracy for PTV D99.9% reduced for the population-HU method, from  -0.1% for ten tissue segments to  -0.4% for three tissue segments, while no such dependence was observed for the ICRU-HU method. Hence, to generate a clinically acceptable plan when using MRI to synthesize CT in the abdomen for treatment planning, it might be sufficient for electron density assignment with either the population-HU or ICRU-HU method to only use three tissue segments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6560/aacfb1DOI Listing
July 2018

Early Response Assessment on Mid-treatment Computed Tomography Predicts for Locoregional Recurrence in Oropharyngeal Cancer Patients Treated With Definitive Radiation Therapy.

Int J Radiat Oncol Biol Phys 2018 11 6;102(4):1036-1045. Epub 2018 Apr 6.

Department of Radiation Oncology, Albert Einstein College of Medicine-Montefiore Medical Center, Bronx, New York. Electronic address:

Purpose: To evaluate whether a response assessment using mid-treatment computed tomography (CT) scans during definitive radiation therapy (RT) for oropharyngeal head and neck cancer can predict for locoregional recurrence (LRR).

Methods And Materials: Head and neck cancer patients who receive RT at our institution undergo CT repeat scans at the 15th fraction, with treatment replanning in the case of an inadequate dose to gross disease or an increased dose to organs at risk. A retrospective cohort analysis was performed of 96 consecutive patients with oropharyngeal cancer treated from 2007 to 2015 with mid-treatment repeat CT scans available. The primary disease volume and involved lymph node volume were delineated on the pre- and mid-treatment CT scans. Univariable and multivariable Cox proportional hazards regression analyses were used to evaluate the efficacy of the mid-treatment reduction in tumor volume as a predictor of LRR. Risk stratification was performed by dichotomizing the patients into high- and low-risk groups according to the mid-treatment response and p16 status and smoking history.

Results: With a median follow-up of 34 months, 14 patients experienced LRR. The median reduction in the total tumor volume was 18.7% (interquartile range 8.4%-30.9%). A reduction in total tumor volume greater than the median was an independent predictor of LRR (hazard ratio 0.22, 95% confidence interval 0.05-0.89; P = .020). The reduction in primary tumor volume was an even stronger predictor of LRR (hazard ratio 0.11, 95% confidence interval 0.02-0.57; P = .002). Stratifying patients into a high-risk group for those with a reduction in the total tumor volume at mid-treatment at or less than the median, p16 negative status, and smoking status of >10 pack-years and a low-risk group for those without these factors, we found a clear separation in Kaplan-Meier curves, with actuarial 3-year locoregional control, progression-free survival, and overall survival rates for the high-risk patients of 45.7%, 38.2%, and 71.8% compared with 90.7%, 70.6%, and 89.8% for low-risk patients, respectively (P ≤ .021 for all).

Conclusions: Our results have shown that the treatment response from an early assessment using mid-treatment CT scans is an independent predictor of LRR and can be used to effectively distinguish high- and low-risk patients, allowing for risk-adaptive treatment stratification at the midway point.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2018.03.059DOI Listing
November 2018

Single- and Multi-Fraction Stereotactic Radiosurgery Dose Tolerances of the Optic Pathways.

Int J Radiat Oncol Biol Phys 2018 Jan 31. Epub 2018 Jan 31.

Department of Radiation Oncology, Lineberger Cancer Center, University of North Carolina, Chapel Hill, North Carolina.

Purpose: Dosimetric and clinical predictors of radiation-induced optic nerve/chiasm neuropathy (RION) after single-fraction stereotactic radiosurgery (SRS) or hypofractionated (2-5 fractions) radiosurgery (fSRS) were analyzed from pooled data that were extracted from published reports (PubMed indexed from 1990 to June 2015). This study was undertaken as part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, investigating normal tissue complication probability (NTCP) after hypofractionated radiation.

Methods And Materials: Eligible studies described dose delivered to optic nerve/chiasm and provided crude or actuarial toxicity risks, with visual endpoints (ie, loss of visual acuity, alterations in visual fields, and/or blindness/complete vision loss). Studies of patients with optic nerve sheath tumors, optic nerve gliomas, or ocular/uveal melanoma were excluded to obviate direct tumor effects on visual outcomes, as were studies not specifying causes of vision loss (ie, tumor progression vs RION).

Results: Thirty-four studies (1578 patients) were analyzed. Histologies included pituitary adenoma, cavernous sinus meningioma, craniopharyngioma, and malignant skull base tumors. Prior resection (76% of patients) did not correlate with RION risk (P = .66). Prior irradiation (6% of patients) was associated with a crude 10-fold increased RION risk versus no prior radiation therapy. In patients with no prior radiation therapy receiving SRS/fSRS in 1-5 fractions, optic apparatus maximum point doses resulting in <1% RION risks include 12 Gy in 1 fraction (which is greater than our recommendation of 10 Gy in 1 fraction), 20 Gy in 3 fractions, and 25 Gy in 5 fractions. Omitting multi-fraction data (and thereby eliminating uncertainties associated with dose conversions), a single-fraction dose of 10 Gy was associated with a 1% RION risk. Insufficient details precluded modeling of NTCP risks after prior radiation therapy.

Conclusions: Optic apparatus NTCP and tolerance doses after single- and multi-fraction stereotactic radiosurgery are presented. Additional standardized dosimetric and toxicity reporting is needed to facilitate future pooled analyses and better define RION NTCP after SRS/fSRS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2018.01.053DOI Listing
January 2018

On the Inclusion of Short-distance Bystander Effects into a Logistic Tumor Control Probability Model.

Cureus 2018 Jan 1;10(1):e2012. Epub 2018 Jan 1.

Department of Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine.

Currently, interactions between voxels are neglected in the tumor control probability (TCP) models used in biologically-driven intensity-modulated radiotherapy treatment planning. However, experimental data suggests that this may not always be justified when bystander effects are important. We propose a model inspired by the Ising model, a short-range interaction model, to investigate if and when it is important to include voxel to voxel interactions in biologically-driven treatment planning. This Ising-like model for TCP is derived by first showing that the logistic model of tumor control is mathematically equivalent to a non-interacting Ising model. Using this correspondence, the parameters of the logistic model are mapped to the parameters of an Ising-like model and bystander interactions are introduced as a short-range interaction as is the case for the Ising model. As an example, we apply the model to study the effect of bystander interactions in the case of radiation therapy for prostate cancer. The model shows that it is adequate to neglect bystander interactions for dose distributions that completely cover the treatment target and yield TCP estimates that lie in the shoulder of the dose response curve. However, for dose distributions that yield TCP estimates that lie on the steep part of the dose response curve or for inhomogeneous dose distributions having significant hot and/or cold regions, bystander effects may be important. Furthermore, the proposed model highlights a previously unexplored and potentially fruitful connection between the fields of statistical mechanics and tumor control probability/normal tissue complication probability modeling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7759/cureus.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5832408PMC
January 2018

Radiation Dose-Volume Effects for Liver SBRT.

Int J Radiat Oncol Biol Phys 2018 Jan 6. Epub 2018 Jan 6.

Radiation Medicine Program, Princess Margaret Cancer Centre and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.

Stereotactic body radiation therapy (SBRT) has emerged as an effective, noninvasive treatment option for primary liver cancer and metastatic disease occurring in the liver. Although SBRT can be highly effective for establishing local control in hepatic malignancies, a tradeoff exists between tumor control and normal tissue complications. The objective of the present study was to review the normal tissue dose-volume effects for SBRT-induced liver and gastrointestinal toxicities and derive normal tissue complication probability models.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2017.12.290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095822PMC
January 2018