Publications by authors named "Teuta Zoto Mustafayev"

15 Publications

  • Page 1 of 1

Stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of liver metastases in oligometastatic patients: initial clinical experience.

Radiat Oncol J 2021 Mar 26;39(1):33-40. Epub 2021 Mar 26.

Department of Radiation Oncology, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey.

Purpose: We aimed to present our initial clinical experience on the implementation of a stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of liver metastases in oligometastatic disease.

Materials And Methods: Twenty-one patients (24 lesions) with liver metastasis treated with SMART were included in this retrospective study. Step-and-shoot intensity-modulated radiotherapy technique was used with daily plan adaptation. During delivery, real-time imaging was used by acquiring planar magnetic resonance images in sagittal plane for monitoring and gating. Acute and late toxicities were recorded both during treatment and follow-up visits.

Results: The median follow-up time was 11.6 months (range, 2.2 to 24.6 months). The median delivered total dose was 50 Gy (range, 40 to 60 Gy); with a median fraction number of 5 (range, 3 to 8 fractions) and the median fraction dose was 10 Gy (range, 7.5 to 18 Gy). Ninety-three fractions (83.7%) among 111 fractions were re-optimized. No patients were lost to follow-up and all patients were alive except one at the time of analysis. All of the patients had either complete (80.9%) or partial (19.1%) response at irradiated sites. Estimated 1-year overall survival was 93.3%. Intrahepatic and extrahepatic progression-free survival was 89.7% and 73.5% at 1 year, respectively. There was no grade 3 or higher acute or late toxicities experienced during the treatment and follow-up course.

Conclusion: SMART represents a new, noninvasive and effective alternative to current ablative radiotherapy methods for treatment of liver metastases in oligometastatic disease with the advantages of better visualization of soft tissue, real-time tumor tracking and potentially reduced toxicity to organs at risk.
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http://dx.doi.org/10.3857/roj.2020.00976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8024184PMC
March 2021

Magnetic resonance image-guided adaptive stereotactic body radiotherapy for prostate cancer: preliminary results of outcome and toxicity.

Br J Radiol 2021 Jan 29;94(1117):20200696. Epub 2020 Oct 29.

Department of Radiation Oncology, Acıbadem MAA University School of Medicine, Istanbul, Turkey.

Objective: Using moderate or ultra-hypofractionation, which is also known as stereotactic body radiotherapy (SBRT) for treatment of localized prostate cancer patients has been increased. We present our preliminary results on the clinical utilization of MRI-guided adaptive radiotherapy (MRgRT) for prostate cancer patients with the workflow, dosimetric parameters, toxicities and prostate-specific antigen (PSA) response.

Methods: 50 prostate cancer patients treated with ultra-hypofractionation were included in the study. Treatment was performed with intensity-modulated radiation therapy (step and shoot) technique and daily plan adaptation using MRgRT. The SBRT consisted of 36.25 Gy in 5 fractions with a 7.25 Gy fraction size. The time for workflow steps was documented. Patients were followed for the acute and late toxicities and PSA response.

Results: The median follow-up for our cohort was 10 months (range between 3 and 29 months). The median age was 73.5 years (range between 50 and 84 years). MRgRT was well tolerated by all patients. Acute genitourinary (GU) toxicity rate of Grade 1 and Grade 2 was 28 and 36%, respectively. Only 6% of patients had acute Grade 1 gastrointestinal (GI) toxicity and there was no Grade ≥ 2 GI toxicity. To date, late Grade 1 GU toxicity was experienced by 24% of patients, 2% of patients experienced Grade 2 GU toxicity and 6% of patients reported Grade 2 GI toxicity. Due to the short follow-up, PSA nadir has not been reached yet in our cohort.

Conclusion: In conclusion, MRgRT represents a new method for delivering SBRT with markerless soft tissue visualization, online adaptive planning and real-time tracking. Our study suggests that ultra-hypofractionation has an acceptable acute and very low late toxicity profile.

Advances In Knowledge: MRgRT represents a new markerless method for delivering SBRT for localized prostate cancer providing online adaptive planning and real-time tracking and acute and late toxicity profile is acceptable.
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http://dx.doi.org/10.1259/bjr.20200696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7774684PMC
January 2021

Magnetic Resonance-Guided Radiation Therapy to Boost Cervical Cancer When Brachytherapy Is Not Available: A Case Report.

Adv Radiat Oncol 2020 Sep-Oct;5(5):1066-1070. Epub 2020 Mar 10.

Department of Radiation Oncology, Mehmet Ali Aydınlar Acıbadem University, School of Medicine, Istanbul, Turkey.

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http://dx.doi.org/10.1016/j.adro.2020.02.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7557129PMC
March 2020

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases.

Neurocirugia (Astur) 2020 Oct 17. Epub 2020 Oct 17.

Department of Radiation Oncology, Acibadem Mehmet Ali Aydinlar University, School of Medicine, Istanbul, Turkey.

Introductio: Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

Patients And Methods: We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

Results: We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

Conclusion: SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.
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http://dx.doi.org/10.1016/j.neucir.2020.08.009DOI Listing
October 2020

Patient-Reported Tolerance of Magnetic Resonance-Guided Radiation Therapy.

Front Oncol 2020 21;10:1782. Epub 2020 Sep 21.

Department of Radiation Oncology, School of Medicine, Mehmet Ali Aydınlar Acıbadem University, Istanbul, Turkey.

Purpose: Magnetic resonance-guided radiation therapy (MRgRT) has been incorporated into a growing number of clinical practices world-wide, however, there is limited data on patient experiences with MRgRT. The purpose of this study was to prospectively evaluate patient tolerance of MRgRT using patient reported outcome questionnaires (PRO-Q).

Methods: Ninety patients were enrolled in this prospective observational study and treated with MRgRT (MRIdian Linac System, ViewRay Inc. Oakwood Village, OH, United States) between September 2018 and September 2019. Breath-hold-gated dose delivery with audiovisual feedback was completed as needed. Patients completed an in-house developed PRO-Q after the first and last fraction of MRgRT.

Results: The most commonly treated anatomic sites were the abdomen (47%) and pelvis (33%). Respiratory gating was utilized in 62% of the patients. Patients rated their experience as positive or at least tolerable with mean scores of 1.0-2.8. The most common complaint was the temperature in the room (61%) followed by paresthesias (57%). The degree of anxiety reported by 45% of the patients significantly decreased at the completion of treatment (mean score 1.54 vs. 1.36, = 0.01). Forty-three percent of the patients reported some degree of disturbing noise which was improved considerably by use of music. All patients appreciated their active role during the treatment.

Conclusion: This evaluation of PROs indicates that MRgRT was well-tolerated by our patients. Patients' experience may further improve with adjustment of room temperature and noise reduction.
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http://dx.doi.org/10.3389/fonc.2020.01782DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7537416PMC
September 2020

Management of symptomatic radiation necrosis after stereotactic radiosurgery and clinical factors for treatment response.

Radiat Oncol J 2020 Sep 14;38(3):176-180. Epub 2020 Jul 14.

Institute of Health Sciences, Mehmet Ali Aydinlar Acibadem University, Istanbul, Turkey.

Purpose: Approximately 10% of patients who received brain stereotactic radiosurgery (SRS) develop symptomatic radiation necrosis (RN). We sought to determine the effectiveness of treatment options for symptomatic RN, based on patient-reported outcomes.

Materials And Methods: We conducted a retrospective review of 217 patients with 414 brain metastases treated with SRS from 2009 to 2018 at our institution. Symptomatic RN was determined by appearance on serial magnetic resonance images (MRIs), MR spectroscopy, requirement of therapy, and development of new neurological complaints without evidence of disease progression. Therapeutic interventions for symptomatic RN included corticosteroids, bevacizumab and/or surgical resection. Patient-reported therapeutic outcomes were graded as complete response (CR), partial response (PR), and no response.

Results: Twenty-six patients experienced symptomatic RN after treatment of 50 separate lesions. The mean prescription dose was 22 Gy (range, 15 to 30 Gy) in 1 to 5 fractions (median, 1 fraction). Of the 12 patients managed with corticosteroids, 6 patients (50%) reported CR and 4 patients (33%) PR. Of the 6 patients managed with bevacizumab, 3 patients (50%) reported CR and 1 patient (18%) PR. Of the 8 patients treated with surgical resection, all reported CR (100%). Other than surgical resection, age ≥54 years (median, 54 years; range, 35 to 81 years) was associated with CR (odds ratio = 8.40; 95% confidence interval, 1.27-15.39; p = 0.027).

Conclusion: Corticosteroids and bevacizumab are commonly utilized treatment modalities with excellent response rate. Our results suggest that patient's age is associated with response rate and could help guide treatment decisions for unresectable symptomatic RN.
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http://dx.doi.org/10.3857/roj.2020.00171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533401PMC
September 2020

New horizons from novel therapies in malignant pleural mesothelioma.

Adv Respir Med 2020 ;88(4):343-351

Department of Radiation Oncology, Acıbadem Maslak Hospital, Istanbul, Turkey.

Malignant pleural mesothelioma (MPM) is a relatively rare, but highly lethal cancer of the pleural mesothelial cells. Its pathoge-nesis is integrally linked to asbestos exposure. In spite of recent developments providing a more detailed understanding of the pathogenesis, the outcomes continue to be poor. To date, trimodality therapy involving surgery coupled with chemotherapy and/or radiotherapy remains the standard of therapy. The development of resistance of the tumor cells to radiation and several che-motherapeutic agents poses even greater challenges in the management of this cancer. Ionizing radiation damages cancer cell DNA and aids in therapeutic response, but it also activates cell survival signaling pathways that helps the tumor cells to overcome radiation-induced cytotoxicity. A careful evaluation of the biology involved in mesothelioma with an emphasis on the workings of pro-survival signaling pathways might offer some guidance for treatment options. This review focuses on the existing treatment options for MPM, novel treatment approaches based on recent studies combining the use of inhibitors which target different pro-survival pathways, and radiotherapy to optimize treatment.
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http://dx.doi.org/10.5603/ARM.a2020.0103DOI Listing
January 2020

Time Analysis of Online Adaptive Magnetic Resonance-Guided Radiation Therapy Workflow According to Anatomical Sites.

Pract Radiat Oncol 2021 Jan-Feb;11(1):e11-e21. Epub 2020 Jul 30.

Department of Radiation Oncology, Acıbadem University School of Medicine, Istanbul, Turkey.

Purpose: To document time analysis of detailed workflow steps for the online adaptive magnetic resonance-guided radiation therapy treatments (MRgRT) with the ViewRay MRIdian system and to identify the barriers to and solutions for shorter treatment times.

Methods And Materials: A total of 154 patients were treated with the ViewRay MRIdian system between September 2018 and October 2019. The time process of MRgRT workflow steps of 962 fractions for 166 treatment sites was analyzed in terms of patient and online adaptive treatment (ART) characteristics.

Results: Overall, 774 of 962 fractions were treated with online ART, and 83.2% of adaptive fractions were completed in less than 60 minutes. Sixty-three percent, 50.3%, and 4.2% of fractions were completed in less than 50 minutes, 45 minutes, and 30 minutes, respectively. Eight-point-three percent and 3% of fractions were completed in more than 70 minutes and 80 minutes, respectively. The median time (t) for ART workflow steps were as follows: (1) setup t: 5.0 minutes, (2) low-resolution scanning t: 1 minute, (3) high-resolution scanning t: 3 minutes, (4) online contouring t: 9 minutes, (5) reoptimization with online quality assurance t: 5 minutes, (6) real targeting t: 3 minutes, (7) beam delivery with gating t: 17 minutes, and (8) net total treatment time t: 45 minutes. The shortest and longest t rates of net total treatment time were 41.59 minutes and 64.43 minutes for upper-lung-lobe-located thoracic tumors and ultracentrally located thoracic tumors, respectively.

Conclusions: To our knowledge, this is the first broad treatment-time analysis for online ART in the literature. Although treatment times are long due to human- and technology-related limitations, benefits offered by MRgRT might be clinically important. In the future, implementation of artificial intelligence segmentation, an increase in dose rate, and faster multileaf collimator and gantry speeds may lead to achieving shorter MRgRT treatments.
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http://dx.doi.org/10.1016/j.prro.2020.07.003DOI Listing
July 2020

Long-term toxicity and survival outcomes after stereotactic ablative radiotherapy for patients with centrally located thoracic tumors.

Radiol Oncol 2020 06 26;54(4):480-487. Epub 2020 Jun 26.

Department of Radiation Oncology, Acibadem MAA University, Istanbul, Turkey.

Background Stereotactic ablative radiotherapy (SABR) is effective for thoracic cancer and metastases; however, adverse effects are greater for central tumors. We evaluated factors affecting outcomes and toxicities after SABR for patients with primary lung and oligometastatic tumors. Patients and methods We retrospectively identified consecutive patients with centrally located lung tumors that were treated at our hospital from 2009-2016. The effects of patient, disease, and treatment-related parameters on local control (LC), overall survival (OS), and toxicity-free survival (TFS) were evaluated with multivariate analyses. Results Among 65 consecutive patients identified with 70 centrally located tumors, 20 tumors (28%) were reirradiated. Median (range) total dose for all tumors was 55 (30-60) Gy in 5 (3-10) fractions. Radiographic complete response was obtained in 43 lesions (61%). None of the analyzed factors were correlated with complete response. After a median follow-up of 57 (95% CI, 48-65) months, 10 tumors (14%) relapsed and 37 patients (57%) died; the actuarial 2- and 5-year OS rates were 52% and 28%, respectively. Median OS was significantly lower in patients with grade 3 or higher toxicity vs. lower toxicity (5 vs. 39 months; P < 0.001). Among 17 severe toxicities, 5 were grade 5, and 3 of them were reirradiated to the same field. Grade 3 to 5 TFS was lower with vs. without reirradiation (2-year TFS, 63% vs. 96%; P = 0.02). Conclusions Our study showed that modern SABR is effective for central lung tumors, and toxicities are acceptable. SABR for reirradiated central lung lesions and possibly for lesions abutting the tracheobronchial tree may result in higher risk of serious toxicities.
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http://dx.doi.org/10.2478/raon-2020-0039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585334PMC
June 2020

Multi-institutional validation of the ESMO-ESGO-ESTRO consensus conference risk grouping in Turkish endometrial cancer patients treated with comprehensive surgical staging.

J Obstet Gynaecol 2021 Apr 29;41(3):414-420. Epub 2020 Apr 29.

Department of Radiation Oncology, Hacettepe University Medical School, Ankara, Turkey.

In this study, 683 patients with endometrial cancer (EC) after comprehensive surgical staging were classified into four risk groups as low (LR), intermediate (IR), high-intermediate (HIR) and high-risk (HR), according to the recent consensus risk grouping. Patients with disease confined to the uterus, ≥50% myometrial invasion (MI) and/or grade 3 histology were treated with vaginal brachytherapy (VBT). Patients with stage II disease, positive/close surgical margins or extra-uterine extension were treated with external beam radiotherapy (EBRT)±VBT. The median follow-up was 56 months. The overall survival (OS) was significantly different between LR and HR groups, and there was a trend between LR and HIR groups. Relapse-free survival (RFS) was significantly different between LR and HIR, LR and HR and IR and HR groups. There was no significant difference in OS and RFS rates between the HIR and HR groups. In HR patients, the OS and RFS rates were significantly higher in stage IB - grade 3 and stage II compared to stage III and non-endometrioid histology without any difference between the two uterine-confined stages and between stage III and non-endometrioid histology. The current risk grouping does not clearly discriminate the HIR and IR groups. In patients with comprehensive surgical staging, a further risk grouping is needed to distinguish the real HR group.Impact statement The standard treatment for endometrial cancer (EC) is surgery and adjuvant radiotherapy (RT) and/or chemotherapy is recommended according to risk factors. The recent European Society for Medical Oncology (ESMO), European Society of Gynaecological Oncology (ESGO) and European Society for Radiotherapy and Oncology (ESTRO) guideline have introduced a new risk group. However, the risk grouping is still quite heterogeneous. This study demonstrated that the current risk grouping recommended by ESMO-ESGO-ESTRO does not clearly discriminate the intermediate risk (IR) and high-intermediate risk (HIR) groups. Based on the results of this study, a new risk grouping can be made to discriminate HIR and IR groups clearly in patients with comprehensive surgical staging.
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http://dx.doi.org/10.1080/01443615.2020.1737661DOI Listing
April 2021

Multichannel Film Dosimetry for Quality Assurance of Intensity Modulated Radiotherapy Treatment Plans Under 0.35 T Magnetic Field.

Cureus 2020 Mar 20;12(3):e7334. Epub 2020 Mar 20.

Radiation Oncology, Acıbadem Hospital, Istanbul, TUR.

Purpose To evaluate the intensity modulated radiotherapy (IMRT) quality assurance (QA) results of the multichannel film dosimetry analysis with single scan method by using Gafchromic™ EBT3 (Ashland Inc., Covington, KY, USA) film under 0.35 T magnetic field. Methods Between September 2018 and June 2019, 70 patients were treated with ViewRay MRIdian (ViewRay Inc., Mountain View, CA) linear accelerator (Linac). Film dosimetry QA plans were generated for all IMRT treatments. Multichannel film dosimetry for red, green and blue (RGB) channels were compared with treatment planning system (TPS) dose maps by gamma evaluation analysis. Results The mean gamma passing rates of RGB channels are 97.3% ± 2.26%, 96.0% ± 3.27% and 96.2% ± 3.14% for gamma evaluation with 2% DD/2 mm distance to agreement (DTA), respectively. Moreover, the mean gamma passing rates of RGB channels are 99.7% ± 0.41%, 99.6% ± 0.59% and 99.5% ± 0.67% for gamma evaluation with 3% DD/3 mm DTA, respectively. Conclusion The patient specific QA using Gafchromic™ EBT3 film with multichannel film dosimetry seems to be a suitable tool to implement for MR-guided IMRT treatments under 0.35 T magnetic field. Multichannel film dosimetry with Gafchromic™ EBT3 is a consistent QA tool for gamma evaluation of the treatment plans even with 2% DD/2 mm DTA under 0.35 T magnetic field presence.
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http://dx.doi.org/10.7759/cureus.7334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164695PMC
March 2020

First 500 Fractions Delivered with a Magnetic Resonance-guided Radiotherapy System: Initial Experience.

Cureus 2019 Dec 24;11(12):e6457. Epub 2019 Dec 24.

Radiation Oncology, Acibadem University School of Medicine, Acibadem Maslak Hospital, Istanbul, TUR.

Objectives Improved soft-tissue visualization, afforded by magnetic resonance imaging integrated into a radiation therapy linear accelerator-based radiation delivery system (MR-linac) promises improved image-guidance. The availability of MR-imaging can facilitate on-table adaptive radiation planning and enable real-time intra-fraction imaging with beam gating without additional exposure to radiation. However, the novel use of magnetic resonance-guided radiation therapy (MRgRT) in the field of radiation oncology also potentially poses challenges for routine clinical implementation. Herein the early experience of a single institution, implementing the first MRgRT system in the country is reported. We aim to describe the workflow and to characterize the clinical utility and feasibility of routine use of an MR-linac system. Methods The ViewRay MRIdian MR-linac system consists of a split-magnet 0.35 T MR-imaging scanner with a double focused multi-leaf collimator (MLC) equipped 6MV linear accelerator. Unique to the system are the control console integrated on-table adaptive radiation therapy (oART) planning capabilities as well as automated beam gating based on real-time intra-fraction MR imaging. From the first day of clinical implementation, oART was performed according to physicians' discretion when medically indicated. All fractions were delivered under real-time imaging with soft tissue-based automated beam gating with individualized gating boundary settings. Patients actively assisted in breath-hold beam gating with the help of custom designed prismatic glasses allowing sight of a computer monitor mounted on the back wall just behind the MRI system bore. Patient demographics and treatment experience, indications for MRgRT including diagnosis and disease site, radiation dose prescribed and fractionation scheme, utilization of oART, respiratory gating settings, as well as duration of each treatment phase were analyzed. Results Between September 2018 and May 2019, 72 patients with 84 tumor sites were treated with MRgRT in 500 total fractions. Median patient age was 66 years (range: 28-83 years). Among 84 tumor sites, the most frequently treated regions were upper abdominal and pelvic (n = 36, 43% and n = 29, 34%, respectively). The most common diagnosis was prostate cancer, with 14 patients treated. In 69 patients (93.2%) oART was used at least once during a treatment course. Twenty-nine targets (43.1%) with significant breathing-related motion were treated in breath-hold with patient visual feedback. Median prescribed dose was 36.25 Gy (range: 24-70 Gy) in median five fractions (range: 3-28 fractions). A gating boundary of 3 mm around a gating region of interest (gROI) was most commonly used (range: 3-5 mm) with 95% of the gROI (range: 93-97%) required to be within the gating boundary for the beam to automatically engage. Mean total treatment time was 47 min (range: 21-125 min) and mean beam-on time was 16.7 min (range: 6-62 min). Conclusions MRgRT afforded by an MR-linac system has been successfully implemented into routine clinical use at our institution as the first system of its kind in Turkey. While the overall number of patients treated and fractions delivered is still limited, we have demonstrated the feasibility of both on-table adaptive radiation therapy as well as automated real-time beam gating on a daily basis in acceptable time schedules.
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http://dx.doi.org/10.7759/cureus.6457DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6977582PMC
December 2019

Evaluation of response to stereotactic radiosurgery in patients with radioresistant brain metastases.

Radiat Oncol J 2019 Dec 31;37(4):265-270. Epub 2019 Dec 31.

Department of Radiation Oncology, School of Medicine, Mehmet Ali Aydinlar Acibadem University, Istanbul, Turkey.

Purpose: Renal cell carcinoma (RCC) and melanoma have been considered 'radioresistant' due to the fact that they do not respond to conventionally fractionated radiation therapy. Stereotactic radiosurgery (SRS) provides high-dose radiation to a defined target volume and a limited number of studies have suggested the potential effectiveness of SRS in radioresistant histologies. We sought to determine the effectiveness of SRS for the treatment of patients with radioresistant brain metastases.

Materials And Methods: We performed a retrospective review of our institutional database to identify patients with RCC or melanoma brain metastases treated with SRS. Treatment response were determined in accordance with the Response Evaluation Criteria in Solid Tumors.

Results: We identified 53 radioresistant brain metastases (28% RCC and 72% melanoma) treated in 18 patients. The mean target volume and coverage was 6.2 ± 9.5 mL and 95.5% ± 2.9%, respectively. The mean prescription dose was 20 ± 4.9 Gy. Forty lesions (75%) demonstrated a complete/partial response and 13 lesions (24%) with progressive/stable disease. Smaller target volume (p < 0.001), larger SRS dose (p < 0.001), and coverage (p = 0.008) were found to be positive predictors of complete response to SRS.

Conclusion: SRS is an effective management option with up to 75% response rate for radioresistant brain metastases. Tumor volume and radiation dose are predictors of response and can be used to guide the decision-making for patients with radioresistant brain metastases.
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http://dx.doi.org/10.3857/roj.2019.00409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952719PMC
December 2019

Output factors of ionization chambers and solid state detectors for mobile intraoperative radiotherapy (IORT) accelerator electron beams.

J Appl Clin Med Phys 2019 Feb 10;20(2):13-23. Epub 2019 Jan 10.

Department of Radiation Oncology, Acıbadem Mehmet Ali Aydınlar University School of Medicine, Istanbul, Turkey.

Purpose: The electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detectors (SS) for electron beam energies generated by LIAC and compare with the output factor of Monte Carlo model (MC) in order to determine the adequate detectors for LIAC .

Methods: The OFs were measured for 6, 8, 10, and 12 MeV electron energies with PTW 23343 Markus, PTW 34045 Advanced Markus, PTW 34001 Roos, IBA PPC05, IBA PPC40, IBA NACP-02, PTW 31010 Semiflex, PTW 31021 Semiflex 3D, PTW 31014 Pinpoint, PTW 60017 Diode E, PTW 60018 Diode SRS, SNC Diode EDGE, and PTW 60019 micro Diamond detectors. Ion recombination factors (k ) of IC were measured for all applicator sizes and OFs were corrected according to k . The measured OFs were compared with Monte Carlo output factors (OF ).

Results: The measured OFs of IBA PPC05, PTW Advanced Markus, PTW Pinpoint, PTW microDiamond, and PTW Diode E detectors are in good agreement with OF . The maximum deviations of IBA PPC05 OFs to OF are -1.6%, +1.5%, +1.5%, and +2.0%; for PTW Advanced Markus +1.0%, +1.5%, +2.0%, and +2.0%; for PTW Pinpoint +2.0%, +1.6%, +4.0%, and +2.0%; for PTW microDiamond -1.6%, +2%, +1.1%, and +1.0%; and for PTW Diode E -+1.7%, +1.7%, +1.3%, and +2.5% for 6, 8, 10, and 12 MeV, respectively. PTW Roos, PTW Markus, IBA PPC40, PTW Semiflex, PTW Semiflex 3D, SNC Diode Edge measured OFs with a maximum deviation of +5.6%, +4.5%, +5.6%, +8.1%, +4.8%, and +9.6% with respect to OF , while PTW Diode SRS and IBA NACP-02 were the least accurate (with highest deviations -37.1% and -18.0%, respectively).

Conclusion: The OFs results of solid state detectors PTW microDiamond and PTW Diode E as well as the ICs with small electrode spacing distance such as IBA PPC05, PTW Advanced Markus and PTW Pinpoint are in excellent agreement with OF . The measurements of the other detectors evaluated in this study are less accurate, thus they should be used with caution. Particularly, PTW Diode SRS and IBA NACP-02 are not suitable and their use should be avoided in relative dosimetry measurements under high dose per pulsed (DPP) electron beams.
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http://dx.doi.org/10.1002/acm2.12522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370992PMC
February 2019

In Regard to Kim et al.

Int J Radiat Oncol Biol Phys 2017 12;99(5):1306-1307

Department of Radiation Oncology, Acibadem University School of Medicine, Maslak, Istanbul, Turkey.

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http://dx.doi.org/10.1016/j.ijrobp.2017.08.034DOI Listing
December 2017