Publications by authors named "Thomas M Guerrero"

18 Publications

  • Page 1 of 1

Synthetic pulmonary perfusion images from 4DCT for functional avoidance using deep learning.

Phys Med Biol 2021 08 23;66(17). Epub 2021 Aug 23.

Beaumont Artificial Intelligence Research Laboratory, Beaumont Health, Royal Oak, MI, United States of America.

To develop and evaluate the performance of a deep learning model to generate synthetic pulmonary perfusion images from clinical 4DCT images for patients undergoing radiotherapy for lung cancer.. A clinical data set of 58 pre- and post-radiotherapyTc-labeled MAA-SPECT perfusion studies (32 patients) each with contemporaneous 4DCT studies was collected. Using the inhale and exhale phases of the 4DCT, a 3D-residual network was trained to create synthetic perfusion images utilizing the MAA-SPECT as ground truth. The training process was repeated for a 50-imaging study, five-fold validation with twenty model instances trained per fold. The highest performing model instance from each fold was selected for inference upon the eight-study test set. A manual lung segmentation was used to compute correlation metrics constrained to the voxels within the lungs. From the pre-treatment test cases ( = 5), 50th percentile contours of well-perfused lung were generated from both the clinical and synthetic perfusion images and the agreement was quantified.. Across the hold-out test set, our deep learning model predicted perfusion with a Spearman correlation coefficient of 0.70 (IQR: 0.61-0.76) and a Pearson correlation coefficient of 0.66 (IQR: 0.49-0.73). The agreement of the functional avoidance contour pairs was Dice of 0.803 (IQR: 0.750-0.810) and average surface distance of 5.92 mm (IQR: 5.68-7.55).. We demonstrate that from 4DCT alone, a deep learning model can generate synthetic perfusion images with potential application in functional avoidance treatment planning.
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August 2021

The Role of Postoperative Radiation Therapy for pN2 Non-small-cell Lung Cancer.

Clin Lung Cancer 2021 01 30;22(1):e5-e17. Epub 2020 Jul 30.

Department of Radiation Oncology, Beaumont Health, Royal Oak, MI. Electronic address:

Background: The role for postoperative radiation therapy (PORT) for patients with non-small-cell lung cancer (NSCLC) with mediastinal lymph node (LN) involvement (pN2 disease) is controversial. We compared surgery alone with PORT among patients with pN2 NSCLC. We then performed subset analyses to better delineate patients that might benefit from PORT.

Patients And Methods: We conducted a propensity score (PS)-matched, inverse probability of treatment weighting (IPTW) Surveillance, Epidemiology, and End Results (SEER) analysis of patients with pN2 disease from 1989 to 2016 with surgery alone or PORT. Multiple imputation with chained equations was used for missing LN data.

Results: A total of 8631 patients were included in this analysis; 4579 underwent surgery alone, and 4052 underwent PORT. Following PS matching and IPTW, there was no difference in overall survival (OS) (hazard ratio [HR], 0.99; P = .76). However, PORT improved OS among a subset of patients with a LN positive to sampled ratio ≥ 50% (HR, 0.90; P = .01). Moreover, there was a trend towards improved OS among this subset, even with chemotherapy (HR, 0.91; P = .09).

Conclusion: PORT is not associated with an improvement or detriment in OS for all patients with pN2 NSCLC. However, patients with a positive to sampled LN ratio ≥ 50% may benefit, regardless of chemotherapy status. Nevertheless, PORT will remain the standard of care as we await the results of the ongoing LUNG ART trial.
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January 2021

Deep convolutional neural networks for automatic segmentation of thoracic organs-at-risk in radiation oncology - use of non-domain transfer learning.

J Appl Clin Med Phys 2020 Jun;21(6):108-113

Beaumont Artificial Intelligence Research Laboratory, Beaumont Health System, Royal Oak, MI, USA.

Purpose: Segmentation of organs-at-risk (OARs) is an essential component of the radiation oncology workflow. Commonly segmented thoracic OARs include the heart, esophagus, spinal cord, and lungs. This study evaluated a convolutional neural network (CNN) for automatic segmentation of these OARs.

Methods: The dataset was created retrospectively from consecutive radiotherapy plans containing all five OARs of interest, including 22,411 CT slices from 168 patients. Patients were divided into training, validation, and test datasets according to a 66%/17%/17% split. We trained a modified U-Net, applying transfer learning from a VGG16 image classification model trained on ImageNet. The Dice coefficient and 95% Hausdorff distance on the test set for each organ was compared to a commercial atlas-based segmentation model using the Wilcoxon signed-rank test.

Results: On the test dataset, the median Dice coefficients for the CNN model vs. the multi-atlas model were 71% vs. 67% for the spinal cord, 96% vs. 94% for the right lung, 96%vs. 94% for the left lung, 91% vs. 85% for the heart, and 63% vs. 37% for the esophagus. The median 95% Hausdorff distances were 9.5  mm vs. 25.3 mm, 5.1  mm vs. 8.1 mm, 4.0  mm vs. 8.0 mm, 9.8  mm vs. 15.8 mm, and 9.2 mm vs. 20.0 mm for the respective organs. The results all favored the CNN model (P < 0.05).

Conclusions: A 2D CNN can achieve superior results to commercial atlas-based software for OAR segmentation utilizing non-domain transfer learning, which has potential utility for quality assurance and expediting patient care.
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June 2020

Metabolic Responses to Metformin in Inoperable Early-stage Non-Small Cell Lung Cancer Treated With Stereotactic Radiotherapy: Results of a Randomized Phase II Clinical Trial.

Am J Clin Oncol 2020 04;43(4):231-235

Department of Radiation Oncology, Division of Radiation Oncology.

Background: Metformin reduces glucose uptake in physiologic tissues and has been shown to affect non-small cell lung cancer (NSCLC) metabolism. We hypothesized that positron emission tomography (PET) scans could detect the impact of metformin on glucose uptake in NSCLC and we sought to test this hypothesis in a prospective clinical trial.

Materials And Methods: A single-blinded phase II clinical trial was performed with subjects randomized 6:1 to 3 to 4 weeks of metformin versus placebo for inoperable early-stage NSCLC. PET scans were performed at baseline, mid-treatment (after 2 wk study medication), and 6 months postradiation. The primary endpoint of the trial was tumor metabolic response to metformin by PERCIST before definitive radiation. Stereotactic body radiotherapy to 50 Gy in 4 fractions was used for peripheral tumors and 70 Gy in 10 fractions for central tumors.

Results: There were 14 subjects randomized to the metformin and 1 to placebo. Histologies were 60% adenocarcinoma, 33.3% squamous cell carcinoma, and 6.7% poorly differentiated carcinoma. At mid-treatment PET scan, 57% of subjects randomized to metformin met PERCIST criteria for metabolic response, of which 75% had progressive metabolic disease and 25% had partial metabolic response, whereas the placebo subject had stable metabolic disease. At 6 months, the metformin arm had 69% complete metabolic response, 23% partial metabolic response and 1 progressive metabolic disease, and the subject treated with placebo had a complete metabolic response. There were no CTCAE grade ≥3 toxicities.

Conclusions: Despite low accrual, majority of subjects treated with metformin had metabolic responses by PERCIST criteria on PET imaging. Contrary to the effect of metformin on most physiologic tissues, most tumors had increased metabolic activity in response to metformin.
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April 2020

High frequency percussive ventilation for respiratory immobilization in radiotherapy.

Tech Innov Patient Support Radiat Oncol 2019 Mar 14;9:8-12. Epub 2018 Dec 14.

William Beaumont Hospital, Department of Radiation Oncology, Royal Oak, MI, United States.

High frequency percussive ventilation (HFPV) employs high frequency low tidal volumes (100-400 bursts/min) to provide respiration in awake patients while simultaneously reducing respiratory motion. The purpose of this study is to evaluate HFPV as a technique for respiratory motion immobilization in radiotherapy. In this study fifteen healthy volunteers (age 30-75 y) underwent HFPV using three different oral interfaces. We evaluated each HFPV oral interface device for compliance, ease of use, comfort, geometric interference, minimal chest wall motion, duty cycle and prolonged percussive time. Their chest wall motion was monitored using an external respiratory motion laser system. The percussive ventilations were delivered via an air driven pneumatic system. All volunteers were monitored for PO and tc-CO with a pulse oximeter and CO Monitoring System. A total of N = 62 percussive sessions were analyzed from the external respiratory motion laser system. Chest-wall motion was well tolerated and drastically reduced using HFPV in each volunteer evaluated. As a result, we believe HFPV may provide thoracic immobilization during radiotherapy, particularly for SBRT and pencil beam scanning proton therapy.
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March 2019

Improved Survival With Increased Time-To-Radiation and Sequential Chemotherapy After Surgery for pN2 Non-Small-cell Lung Cancer.

Clin Lung Cancer 2018 03 20;19(2):e185-e194. Epub 2017 Nov 20.

Department of Radiation Oncology, Beaumont Health, Oakland University William Beaumont School of Medicine, Royal Oak, MI. Electronic address:

Background: Currently, the ideal timing for postoperative radiotherapy (PORT) and chemotherapy is unknown. The present study evaluated their relative timing on overall survival (OS) using the National Cancer Database (NCDB).

Materials And Methods: The NCDB was queried for patients from 2004 to 2012 with resected non-small-cell lung cancer (NSCLC), pathologically involved N2 (pN2) nodes, and negative margins. All patients underwent adjuvant chemotherapy and external beam radiotherapy. The time to radiation (TTR) was determined from the date of surgery to the start of PORT, with the exclusion of those receiving PORT < 4 weeks or > 24 weeks postoperatively. Early and late TTR was dichotomized at 8 weeks after receiver operating characteristic analysis. Multivariate Cox regression analysis was conducted to predict the variables significantly associated with survival.

Results: A total of 1629 patients were eligible for analysis. Of the 1629 patients, 703 had received PORT < 8 weeks and 926 had received PORT ≥ 8 weeks postoperatively. The receipt of PORT after 8 weeks was associated with better OS (P = .0044). No significant differences were found in survival in the concurrent group comparing early and later TTR (P = .9119). However, a significant OS benefit was found for sequential chemotherapy with an increased TTR (P = .0045). Older age, male sex, shorter distance traveled, increased nodal positivity, larger tumor size, higher Charlson/Deyo comorbidity score, and early TTR were associated with inferior survival on multivariate analysis.

Conclusion: A TTR of ≥ 8 weeks with sequential chemotherapy in the setting of PORT was associated with improved survival in patients with NSCLC with pN2 nodes.
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March 2018

Pre-Radiation Therapy Fluorine 18 Fluorodeoxyglucose PET Helps Identify Patients with Esophageal Cancer at High Risk for Radiation Pneumonitis.

Radiology 2015 Jun 13;275(3):822-31. Epub 2015 Jan 13.

From the Department of Radiation Oncology, The University of Texas Medical Branch, Galveston, Tex (R.C.); Department of Radiation Oncology, Baylor College of Medicine, Houston, Tex (N.P.); Department of Radiation Oncology, Beaumont Health System, 3601 W Thirteen Mile Rd, Royal Oak, MI 48073-6769 (E.C., T.M.G.); Department of Computational and Applied Mathematics, Rice University, Houston, Tex (E.C., T.M.G.); Department of Pulmonology, Bellvitge Hospital, University of Barcelona, Barcelona, Spain (S.A.G.); Department of Radiation Oncology, University of Chicago, Chicago, Ill (S.A.); and Divisions of Quantitative Sciences (B.H.), Diagnostic Imaging (D.P.), and Radiation Oncology (H.S.), The University of Texas MD Anderson Cancer Center, Houston, Texas.

Purpose: To examine the association between pre-radiation therapy (RT) fluorine 18 fluorodeoxyglucose (FDG) uptake and post-RT symptomatic radiation pneumonitis (RP).

Materials And Methods: In accordance with the retrospective study protocol approved by the institutional review board, 228 esophageal cancer patients who underwent FDG PET/CT before chemotherapy and RT were examined. RP symptoms were evaluated by using the Common Terminology Criteria for Adverse Events, version 4.0, from the consensus of five clinicians. By using the cumulative distribution of standardized uptake values (SUVs) within the lungs, those values greater than 80%-95% of the total lung voxels were determined for each patient. The effect of pre-chemotherapy and RT FDG uptake, dose, and patient or treatment characteristics on RP toxicity was studied by using logistic regression.

Results: The study subjects were treated with three-dimensional conformal RT (n = 36), intensity-modulated RT (n = 135), or proton therapy (n = 57). Logistic regression analysis demonstrated elevated FDG uptake at pre-chemotherapy and RT was related to expression of RP symptoms. Study subjects with elevated 95% percentile of the SUV (SUV95) were more likely to develop symptomatic RP (P < .000012); each 0.1 unit increase in SUV95 was associated with a 1.36-fold increase in the odds of symptomatic RP. Receiver operating characteristic (ROC) curve analysis resulted in area under the ROC curve of 0.676 (95% confidence interval: 0.58, 0.77), sensitivity of 60%, and specificity of 71% at the 1.17 SUV95 threshold. CT imaging and dosimetric parameters were found to be poor predictors of RP symptoms.

Conclusion: The SUV95, a biomarker of pretreatment pulmonary metabolic activity, was shown to be prognostic of symptomatic RP. Elevation in this pretreatment biomarker identifies patients at high risk for posttreatment symptomatic RP.
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June 2015

Quality assurance assessment of diagnostic and radiation therapy-simulation CT image registration for head and neck radiation therapy: anatomic region of interest-based comparison of rigid and deformable algorithms.

Radiology 2015 Mar 7;274(3):752-63. Epub 2014 Nov 7.

From the Departments of Radiation Oncology (A.S.R.M., M.N.R., M.J.A., C.A.B., R.C., E.C., T.M.G., E.K.U., J.Y., L.C., M.E.K., G.B.G., S.J.F., A.S.G., D.I.R., C.D.F.) and Radiology (R.R.C.), University of Texas MD Anderson Cancer Center, Box 0097, 1515 Holcombe Blvd, Houston, TX 77030; Department of Radiology and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, Mass (J.K.C.); Department of Computational and Applied Mathematics, Rice University, Houston, Tex (R.C., E.C., T.M.G.); and Graduate School of Biomedical Science, University of Texas Health Science Center, Houston, Tex (E.C., T.M.G., L.C., C.D.F.).

Purpose: To develop a quality assurance (QA) workflow by using a robust, curated, manually segmented anatomic region-of-interest (ROI) library as a benchmark for quantitative assessment of different image registration techniques used for head and neck radiation therapy-simulation computed tomography (CT) with diagnostic CT coregistration.

Materials And Methods: Radiation therapy-simulation CT images and diagnostic CT images in 20 patients with head and neck squamous cell carcinoma treated with curative-intent intensity-modulated radiation therapy between August 2011 and May 2012 were retrospectively retrieved with institutional review board approval. Sixty-eight reference anatomic ROIs with gross tumor and nodal targets were then manually contoured on images from each examination. Diagnostic CT images were registered with simulation CT images rigidly and by using four deformable image registration (DIR) algorithms: atlas based, B-spline, demons, and optical flow. The resultant deformed ROIs were compared with manually contoured reference ROIs by using similarity coefficient metrics (ie, Dice similarity coefficient) and surface distance metrics (ie, 95% maximum Hausdorff distance). The nonparametric Steel test with control was used to compare different DIR algorithms with rigid image registration (RIR) by using the post hoc Wilcoxon signed-rank test for stratified metric comparison.

Results: A total of 2720 anatomic and 50 tumor and nodal ROIs were delineated. All DIR algorithms showed improved performance over RIR for anatomic and target ROI conformance, as shown for most comparison metrics (Steel test, P < .008 after Bonferroni correction). The performance of different algorithms varied substantially with stratification by specific anatomic structures or category and simulation CT section thickness.

Conclusion: Development of a formal ROI-based QA workflow for registration assessment demonstrated improved performance with DIR techniques over RIR. After QA, DIR implementation should be the standard for head and neck diagnostic CT and simulation CT allineation, especially for target delineation.
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March 2015

Metformin use and improved response to therapy in esophageal adenocarcinoma.

Acta Oncol 2013 Jun 5;52(5):1002-9. Epub 2012 Sep 5.

Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.

Background: We investigated the radiographic and pathologic response rate of esophageal adenocarcinoma treated with neoadjuvant chemoradiation in patients taking metformin.

Material And Methods: Two hundred eighty-five patients with esophageal adenocarcinoma treated with concurrent chemoradiation (CRT) followed by esophagectomy from 1997 to 2012 were included in the study, including 29 diabetics taking metformin, 21 diabetics not taking metformin and 235 non-diabetics. Pre- and post-treatment positron emission tomography (PET) scans were available for 204 patients. Pathologic response was graded at the time of surgery. Response rates were compared using both the χ(2) statistic as well as ANOVA with post-hoc LSD analysis. Multivariate logistic regression analysis was performed to control for predictors of pathologic complete response (CR) after CRT.

Results: The overall rate of pathologic CR for the study population was 20%. The pathologic CR rate was higher in patients taking metformin (34.5%), compared to diabetic patients not taking metformin (4.8%, p = 0.01) and non-diabetic patients (19.6%, p = 0.05). Pathologic CR was related to metformin dose, with ≥ 1500 mg/d associated with a higher CR rate. No significant difference seen in pre-CRT maximum tumor SUV (p = 0.93), however post-CRT maximum SUV was significantly decreased in patients taking metformin (p = 0.05). On multivariate logistic regression, metformin use was independently associated with pathologic CR (p = 0.04). Metformin use was also associated with decreased in field loco-regional failure following radiation (p = 0.05).

Conclusion: Metformin use is associated with a dose-dependent increased response to CRT in esophageal cancer and may be a sensitizer to this therapy.
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June 2013

Four-dimensional computed tomography-based treatment planning for intensity-modulated radiation therapy and proton therapy for distal esophageal cancer.

Int J Radiat Oncol Biol Phys 2008 Sep;72(1):278-87

Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To compare three-dimensional (3D) and four-dimensional (4D) computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing.

Methods And Materials: The IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing.

Results: Compared with IMRT, median lung volumes exposed to 5, 10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%, 5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%, 5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index [CI], 1.99) and greater irradiation of the heart (heart-V40, 41.8%) compared with the IMRT plan(CI, 1.55, heart-V40, 35.7%) or the three-beam proton plan (CI, 1.46, heart-V40, 27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas filling.

Conclusions: Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.
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September 2008

Radiation pneumonitis: correlation of toxicity with pulmonary metabolic radiation response.

Int J Radiat Oncol Biol Phys 2008 Jul 19;71(4):967-71. Epub 2008 May 19.

Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To characterize the relationship between radiation pneumonitis (RP) clinical symptoms and pulmonary metabolic activity on post-treatment [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET).

Patients And Methods: We retrospectively studied 101 esophageal cancer patients who underwent restaging FDG-PET/computed tomography imaging 3-12 weeks after completing thoracic radiotherapy. The National Institutes of Health Common Toxicity Criteria, version 3, was used to score the RP clinical symptoms. Linear regression was applied to the FDG-PET/computed tomography images to determine the normalized FDG uptake vs. radiation dose. The pulmonary metabolic radiation response (PMRR) was quantified as this slope. Modeling was performed to determine the interaction of PMRR, mean lung dose (MLD), and the percentage of lung receiving >20 Gy with RP outcomes.

Results: Of the 101 patients, 25 had Grade 0, 10 had Grade 1, 60 had Grade 2, 5 had Grade 3, and 1 had Grade 5 RP symptoms. Logistic regression analysis demonstrated that increased values of both MLD and PMRR were associated with a greater probability of RP clinical symptoms (p = 0.032 and p = 0.033, respectively). Spearman's rank correlation found no association between the PMRR and the dosimetric parameters (planning target volume, MLD, percentage of lung receiving >5-30 Gy). Twofold cross-validation demonstrated that the combination of MLD and PMRR was superior to either alone for assessing the development of clinical RP symptoms. The combined MLD (or percentage of lung receiving >20 Gy) and PMRR had a greater sensitivity and accuracy (53.3% and 62.5%, respectively) than either alone.

Conclusion: The results of this study have demonstrated a significant correlation between RP clinical symptoms and the PMRR measured by FDG-PET/computed tomography after thoracic radiotherapy.
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July 2008

Four-dimensional cone beam CT with adaptive gantry rotation and adaptive data sampling.

Med Phys 2007 Sep;34(9):3520-9

Department of Imaging Physics, M.D. Anderson Cancer Center, The University of Texas, Houston, Texas 77030, USA.

We have developed a new four-dimensional cone beam CT (4D-CBCT) on a Varian image-guided radiation therapy system, which has radiation therapy treatment and cone beam CT imaging capabilities. We adapted the speed of gantry rotation time of the CBCT to the average breath cycle of the patient to maintain the same level of image quality and adjusted the data sampling frequency to keep a similar level of radiation exposure to the patient. Our design utilized the real-time positioning and monitoring system to record the respiratory signal of the patient during the acquisition of the CBCT data. We used the full-fan bowtie filter during data acquisition, acquired the projection data over 200 deg of gantry rotation, and reconstructed the images with a half-scan cone beam reconstruction. The scan time for a 200-deg gantry rotation per patient ranged from 3.3 to 6.6 min for the average breath cycle of 3-6 s. The radiation dose of the 4D-CBCT was about 1-2 times the radiation dose of the 4D-CT on a multislice CT scanner. We evaluated the 4D-CBCT in scanning, data processing and image quality with phantom studies. We demonstrated the clinical applicability of the 4D-CBCT and compared the 4D-CBCT and the 4D-CT scans in four patient studies. The contrast-to-noise ratio of the 4D-CT was 2.8-3.5 times of the contrast-to-noise ratio of the 4D-CBCT in the four patient studies.
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September 2007

Determination of respiratory motion for distal esophagus cancer using four-dimensional computed tomography.

Int J Radiat Oncol Biol Phys 2008 Jan 12;70(1):145-53. Epub 2007 Sep 12.

Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To investigate the motion characteristics of distal esophagus cancer primary tumors using four-dimensional computed tomography (4D CT).

Methods And Materials: Thirty-one consecutive patients treated for esophagus cancer who received respiratory-gated 4D CT imaging for treatment planning were selected. Deformable image registration was used to map the full expiratory motion gross tumor volume (GTV) to the full-inspiratory CT image, allowing quantitative assessment of each voxel's displacement. These displacements were correlated with patient tumor and respiratory characteristics.

Results: The mean (SE) tidal volume was 608 (73) mL. The mean GTV volume was 64.3 (10.7) mL on expiration and 64.1 (10.7) mL on inspiration (no significant difference). The mean tumor motion in the x-direction was 0.13 (0.006) cm (average of absolute values), in the y-direction 0.23 (0.01) cm (anteriorly), and in the z-direction 0.71 (0.02) cm (inferiorly). Tumor motion correlated with tidal volume. Comparison of tumor motion above vs. below the diaphragm was significant for the average net displacement (p = 0.014), motion below the diaphragm was greater than above. From the cumulative distribution 95% of the tumors moved less than 0.80 cm radially and 1.75 cm inferiorly.

Conclusions: Primary esophagus tumor motion was evaluated with 4D CT. According to the results of this study, when 4D CT is not available, a radial margin of 0.8 cm and axial margin of +/-1.8 cm would provide tumor motion coverage for 95% of the cases in our study population.
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January 2008

Comparison of outcomes for patients with unresectable, locally advanced non-small-cell lung cancer treated with induction chemotherapy followed by concurrent chemoradiation vs. concurrent chemoradiation alone.

Int J Radiat Oncol Biol Phys 2007 Jul 6;68(3):779-85. Epub 2007 Apr 6.

Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To retrospectively compare outcomes for patients with unresectable locally advanced non-small-cell lung cancer (NSCLC) treated at our institution with concurrent chemoradiation with or without induction chemotherapy.

Methods And Materials: We retrospectively analyzed 265 consecutive patients who received definitive treatment with three-dimensional conformal radiation and concurrent chemotherapy. Of these, 127 patients received induction chemotherapy before concurrent chemoradiation.

Results: The two groups of patients (with induction vs. without induction chemotherapy) were similar in age, performance status, weight loss, histology, grade, and stage. Patients who received induction chemotherapy had better overall survival (median, 1.9 vs. 1.4 years; 5-year rate, 25% vs. 12%; p < 0.001) and distant metastasis-free survival (5-year rate, 42% vs. 23%; p = 0.021). Locoregional control was not significantly different between the two groups. Multivariate analysis showed that induction chemotherapy was the most significant factor affecting overall survival, with a hazard ratio of 0.55 (95% confidence interval 0.40-0.75; p < 0.001). A planned subgroup analysis showed that induction chemotherapy was associated with a significant overall survival benefit for patients with adenocarcinoma or large-cell carcinoma (5-year rate, 24% vs. 8%; p = 0.003) but not for those with squamous cell carcinoma. A multivariate analysis of patients with adenocarcinoma or large-cell carcinoma confirmed that induction chemotherapy was the most significant factor associated with better overall survival, with a hazard ratio of 0.47 (95% confidence interval, 0.28-0.78; p = 0.003).

Conclusion: Our retrospective analysis suggests that in combination with concurrent chemoradiation, induction chemotherapy may provide a small but significant survival benefit for patients with unresectable locally advanced adenocarcinoma or large-cell carcinoma of the lung.
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July 2007

Reduction of normal lung irradiation in locally advanced non-small-cell lung cancer patients, using ventilation images for functional avoidance.

Int J Radiat Oncol Biol Phys 2007 Jun 29;68(2):562-71. Epub 2007 Mar 29.

Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To investigate the ability of four-dimensional computed tomography (4D-CT)-derived ventilation images to identify regions of highly functional lung for avoidance in intensity-modulated radiotherapy (IMRT) planning in locally advanced non-small-cell lung cancer (NSCLC).

Methods And Materials: The treatment-planning records from 21 patients with Stage III NSCLC were selected. Ventilation images were generated from the 4D-CT sets, and each was imported into the treatment-planning system. Ninetieth percentile functional volumes (PFV90), constituting the 10% of the lung volume where the highest ventilation occurs, were generated. Baseline IMRT plans were generated using the lung volume constraint on V20 (<35%), and two additional plans were generated using constraints on the PFV90 without a volume constraint. Dose-volume and dose-function histograms (DVH, DFH) were generated and used to evaluate the planning target volume coverage, lung volume, and functional parameters for comparison of the plans.

Results: The mean dose to the PFV90 was reduced by 2.9 Gy, and the DFH at 5 Gy (F5) was reduced by 9.6% (SE = 2.03%). The F5, F10, V5, and V10 were all significantly reduced from the baseline values. We identified a favorable subset of patients for whom there was a further significant improvement in the mean lung dose.

Conclusions: Four-dimensional computed tomography-derived ventilation regions were successfully used as avoidance structures to reduce the DVH and DFH at 5 Gy in all cases. In a subset, there was also a reduction in the F10 and V10 without a change in the V20, suggesting that this technique could be safely used.
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June 2007

Feasibility of using intensity-modulated radiotherapy to improve lung sparing in treatment planning for distal esophageal cancer.

Radiother Oncol 2005 Dec 17;77(3):247-53. Epub 2005 Nov 17.

Department of Radiation Oncology, University of Texas, M.D. Anderson Cancer Center, Houston, USA.

Background And Purpose: To evaluate the feasibility whether intensity-modulated radiotherapy (IMRT) can be used to reduce doses to normal lung than three-dimensional conformal radiotherapy (3 DCRT) in treating distal esophageal malignancies.

Patients And Methods: Ten patient cases with cancer of the distal esophagus were selected for a retrospective treatment-planning study. IMRT plans using four, seven, and nine beams (4B, 7B, and 9B) were developed for each patient and compared with the 3 DCRT plan used clinically. IMRT and 3 DCRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures, with statistical comparison made between the two types of plans using the Wilcoxon matched-pair signed-rank test.

Results: IMRT plans (4B, 7B, 9B) reduced total lung volume treated above 10 Gy (V(10)), 20 Gy (V(20)), mean lung dose (MLD), biological effective volume (V(eff)), and lung integral dose (P<0.05). The median absolute improvement with IMRT over 3DCRT was approximately 10% for V(10), 5% for V(20), and 2.5 Gy for MLD. IMRT improved the PTV heterogeneity (P<0.05), yet conformity was better with 7B-9B IMRT plans. No clinically meaningful differences were observed with respect to the irradiated volumes of spinal cord, heart, liver, or total body integral doses.

Conclusions: Dose-volume of exposed normal lung can be reduced with IMRT, though clinical investigations are warranted to assess IMRT treatment outcome of esophagus cancers.
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December 2005

Intensity-modulated radiation therapy for mesothelioma: impact of multileaf collimator leaf width and pencil beam size on planning quality and delivery efficiency.

Int J Radiat Oncol Biol Phys 2005 Aug;62(5):1525-34

Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To compare treatment plans for multileaf collimators (MLCs) with different leaf widths and different finite pencil beam (FPB) sizes, to determine the planning quality and delivery efficiency of segmented MLC (SMLC) delivery of intensity-modulated radiation therapy (IMRT) for malignant pleural mesothelioma (MPM).

Methods And Materials: Computerized tomography images of 10 right-side MPM patients were used for this planning study on a CORVUS treatment-planning system (NOMOS Corporation, Sewickley, PA) for a Varian Millennium 120-MLC (Varian Medical Systems, Palo Alto, CA). Three beam models were used. The first model forced two 0.5-cm MLC leaves to move in tandem to simulate a 1-cm leaf-width MLC and a FPB size of 1 x 1 cm2. The second model used 0.5-cm leaves with a FPB size of 0.5 x 1 cm2 (1 cm in the direction of leaf movement). The third model used 0.5-cm leaves, with a FPB size of 0.5 x 0.5 cm2. For optimization, the same dose constraints and beam parameters were used for each data set. Tissue heterogeneity corrections were used during optimization and dose calculation. Plans were optimized such that the clinical target volume received 50 Gy in 25 fractions. Dose distributions to the target and normal structures were evaluated. The number of monitor units, the number of segments, and delivery times were used to evaluate delivery efficiency.

Results: All three beam models could be used for IMRT planning for MPM. The doses to clinical target volume, spinal cord, lung, liver, heart, and contralateral kidney were acceptable with all three beam models. The 0.5 x 0.5-cm2 beam model used the most monitor units (6883 +/- 974 vs. 3332 +/- 406 and 3407 +/- 443 for the 1 x 1-cm2 and 0.5 x 1-cm2 models, respectively) and treated the most segments (4297 +/- 802 vs. 1357 +/- 156 and 1767 +/- 212 for the 1 x 1-cm2 and 0.5 x 1-cm2 models, respectively). The plan generated with the 1 x 1-cm2 model required the least amount of time to deliver.

Conclusions: The quality of the MPM IMRT plans generated with the three beam models presented here was similar; however, the 1 x 1-cm2 model provided the most efficient delivery of MPM IMRT with the CORVUS planning system.
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August 2005

Feasibility of sparing lung and other thoracic structures with intensity-modulated radiotherapy for non-small-cell lung cancer.

Int J Radiat Oncol Biol Phys 2004 Mar;58(4):1268-79

Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

Purpose: To investigate the possibility of using intensity-modulated radiotherapy (IMRT) to reduce the irradiated volumes of the normal lung and other critical structures in the treatment of non-small-cell lung cancer (NSCLC) and to investigate the effect of IMRT on the potential of spreading low doses to large volumes of normal tissues in such treatment.

Methods And Materials: A retrospective treatment planning study was performed to compare IMRT and conventional three-dimensional conformal radiation therapy (3D-CRT) for 10 NSCLC patients (Stage I-IIIB). In the IMRT plans, three to nine coplanar beams were designed to treat 95% of the planning target volume with 63 Gy and to minimize the volumes of the normal lung, esophagus, heart, and spinal cord irradiated above their tolerance doses. The two types of plans were compared with respect to the planning target volume coverage, dose-volume histograms, and other dosimetric indexes of the normal structures.

Results: Comparing the nine-beam IMRT plan with the 3D-CRT plan, the percentage of lung volume that received >20 Gy and the mean lung dose were reduced for all cases, with a median reduction of 8% and 2 Gy, respectively. An additional reduction of the >5-Gy volume and >10-Gy volume for the lung and thoracic tissue was more difficult with IMRT, although still possible using fewer beams in IMRT. The integral dose to the entire thorax was equivalent and even reduced for 8 of 10 cases using IMRT.

Conclusion: It is possible to reduce the volumes of low doses (such as the >10-Gy volume and >20-Gy volume) for thoracic normal tissues using IMRT. The increased integral dose and low-dose volumes can be avoided for IMRT if such concerns are addressed carefully in the inverse planning process and with optimization of the IMRT beam configuration.
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March 2004