- Email: [email protected]
Can MRI-derived Factors Predict Survival in Patients with Glioblastoma Multiforme?
Proceedings of the 53rd Annual ASTRO Meeting
2130
A Feasibility Trial of Concurrent Radiation, Temozolomide, and Bevacizumab Followed by Temozolomide and Bevacizumab for Resectable and Unresectable Glioblastoma Multiforme of the Brain
R. H. Liebross1,2, R. Birhiray2,3, S. Schultz2,4, T. Payner2,5, N. Gupta2,4, R. Young2,5, A. Cohen-Gadol2,5, B. Kuzma2,6, S. Givens1,2, C. Leagre1,2 1 Cancer Care Group, LLC, Indianapolis, IN, 2St. Vincent Hospital, Indianapolis, IN, 3Hematology Oncology of Indiana, Indianapolis, IN, 4American Health Network, Indianapolis, IN, 5Goodman Campbell Brain and Spine, Indianapolis, IN, 6 Northwest Radiology, Indianapolis, IN
Purpose/Objective(s): The use of Bevacizumab (BV) for recurrent high grade gliomas has been promising. We hypothesized based on second line treatment efficacy that incorporating radiation therapy (RT), temozolomide (TMZ) and BV for the primary treatment of glioblastoma multiforme would improve clinical outcomes. The primary objective of this study is to evaluate the median time to progression and secondarily median survival, safety and toxicity. Materials/Methods: Following maximal surgery, if possible, all patients received 61.2 Gy of RT. Concurrently TMZ was given daily (7days/week) at 75 mg/m2 and BV was delivered at 5 mg/kg every 2 weeks. After a 1 month interval upon completion of RT, and MRI of the brain was obtained and the post-RT phase commenced with TMZ at 150 mg/m2 for 5 days every 4 weeks and resumption of BV at 10 mg/kg IV every 2 weeks for a total of 6 months. Results: Thirty-six of 36 enrolled patients have completed protocol therapy. No brain hemorrhages were seen. Five patients developed deep venous thrombosis while on therapy. Three patients had a pulmonary embolism. 5 patients developed neutropenia and 2 of these had pancytopenia. Nine patients had thrombocytopenia. One patient with a history of multiple anal fistulas had a recurrence under treatment. Two patients developed impaired wound healing. The median follow up of patients was 10 months. The median progression free and overall survival were 15 and 16 months, respectively. Conclusions: Early data from treatment with maximal surgery (if possible) followed by RT, TMZ and BV concurrently followed by adjuvant TMZ and BV indicate feasibility. The progression free survival appears promising indicating a potential need for continued maintenance therapy for patients with glioblastoma multiforme. Author Disclosure: R.H. Liebross: None. R. Birhiray: None. S. Schultz: None. T. Payner: None. N. Gupta: None. R. Young: None. A. Cohen-Gadol: None. B. Kuzma: None. S. Givens: None. C. Leagre: None.
2131
MGMT Gene Promoter Methylation Status as a Potent Prognostic Factor in Glioblastoma Treated with Temozolomide Chemo-irradiation
Y. Kim, S. Kim, J. Kim, J. Cho, J. Chang, D. Kim, K. Lee, C. Suh Severance Hospital, Seoul, Korea, Republic of Korea Purpose/Objective(s): The current standard of care for newly diagnosed glioblastoma (GBM) is surgical resection followed by involved-field radiotherapy (RT) with temozolomide (TMZ). Recently, cells that are deficient in O6-methylguanine-DNA methyltransferase (MGMT) have been found to show an increased sensitivity to TMZ, and methylation of the MGMT promoter has been suggested as a predictive marker for GBM. We evaluated whether the methylation status of the MGMT gene promoter affected survival in GBM patients. Materials/Methods: We retrospectively analyzed the cases of 93 patients with histologically confirmed GBM between Jan 2001 and Dec 2008. The patients received post-operative RT with TMZ. The age range was 24-78 yrs (median 58 yrs). Surgical resection was total in 39 patients (42%), subtotal in 30 patients (32%), and partial in 17 patients (18%), while a biopsy only was performed in 7(8%) patients. RT doses ranged from 50-74 Gy (median 70 Gy). The MGMT gene promoter methylation status could be identified in 78 patients; it was unmethylated in 43 patients (55%) and methylated in 35 (45%). In the remaining 15 pts, tissue was not available or the test results were inconclusive. There was no statistically significant difference in terms of clinical characteristics between the methylated and unmethylated MGMT gene promoter groups. Results: All patients were followed-up until death or analyzing time (3-88 months, median 22). Median overall survival was 22 months and progression-free survival was 11 months. The two-year and five-year survival rates were 36% and 15%. MGMT gene promoter methylation status (p = .002) and age (p = .006) were statistically significant prognostic factors for overall survival on both the univariate and multivariate analyses. The median survival for the methylated group was 29 months, and 20 months for the unmethylated group. In 35 pts with methylated MGMT promoter, the two-year and five-year survival rates were 54% and 31%, respectively. Long-term survivors ($ 3-years) were more frequent in the methylated group. (11/35 in methylated group vs 4/43 in unmethylated group). The extent of surgical resection affected progression-free survival. Among the pts who received total or subtotal resections, six pts who were 50 yrs old or younger and showed methylated MGMT, were all alive 38 to 77 months after operation (median 49 months). In contrast, 21 pts who received total or subtotal resections, were older than 50 yrs old, and had unmethylated MGMT, showed only 18 months of median survival. Performance status and RT dose were not significant prognostic factors. Conclusions: In addition to age and extent of surgical resection, MGMT gene promoter methylation status was found to be a potent prognostic factor for GBM, in a study at a single Korean institution. Author Disclosure: Y. Kim: None. S. Kim: None. J. Kim: None. J. Cho: None. J. Chang: None. D. Kim: None. K. Lee: None. C. Suh: None.
2132
Can MRI-derived Factors Predict Survival in Patients with Glioblastoma Multiforme?
R. Murakami1, H. Nakamura2, T. Hirai3, M. Kitajima3, Y. Nakaguchi1, S. Nishimura3, H. Uetani3, J. Kuratsu2, Y. Yamashita3 1 Department of Medical Imaging, Kumamoto University, Kumamoto, Japan, 2Department of Neurosurgery, Kumamoto University, Kumamoto, Japan, 3Department of Diagnostic Radiology, Kumamoto University, Kumamoto, Japan
Purpose/Objective(s): Patients with glioblastoma multiforme (GBM) are usually treated with surgery followed by a combination of radiation therapy (RT) and chemotherapy. Because of the heterogeneous nature of the disease, a large number of factors can
S275
I. J. Radiation Oncology d Biology d Physics
S276
Volume 81, Number 2, Supplement, 2011
potentially influence the prognosis. Furthermore, advanced diagnostic and therapeutic developments may provide novel prognostic factors. As a pretreatment variable, diffusion-weighted (DW) magnetic resonance imaging (MRI) with quantitative apparent diffusion coefficient (ADC) can be a clinical biomarker. Many neurosurgeons advocate tumor resection as extensive as possible and early postoperative MRI within 72 hr after surgery is thought to reliably detect residual tumors. The purpose of this study was to determine which factors can predict survival more convincingly in patients with GBM. Materials/Methods: Between January 2000 and September 2009, 138 patients with GBM underwent postoperative RT and longitudinal MRI preoperatively, in the early postoperative period, and at 1-month intervals thereafter until recurrence. On early postoperative MRI, the surgical status was classified into biopsy, partial resection (PR), and gross total resection (GTR). Patient age, Karnofsky performance scale (KPS) score, minimum ADC, and surgical status were assessed by factor analysis of overall survival (OS). Radiation therapy oncology group-recursive partitioning analysis (RTOG-RPA) criteria were used to validate prognostic values of the MRI-derived factors, i.e., minimum ADC and surgical status. Kaplan-Meier survival curves, the log-rank test, and the multivariate Cox proportional hazards model were used to evaluate the prognostic factors. Results: Median OS associated with low (\ 0.9310 3 mm2/sec) and high ($ 0.9310 3 mm2/sec) minimum ADC was 11.2 and 18.0 months, respectively (p \ 0.001). According to surgical status, median OS associated with biopsy or PR and GTR was 11.7 and 18.9 months, respectively (p\0.001). Substantial independent prognostic factors were KPS score (hazard ratio = 1.812; 95% confidence interval (CI), 1.185-2.771), minimum ADC (2.365; 95% CI, 1.482-3.776), and surgical status (1.777; 95% CI, 1.073-2.943). The MRI-derived factors assigned patients to different prognostic groups in RTOG-RPA classes and stratified into high risk of low minimum ADCs with residual tumors, low risk of high minimum ADCs without residual tumors, and intermediate risk of the others. Median OS among low, intermediate, and high risk group was 28.2, 14.7, and 10.8 months, respectively (p \ 0.001). Conclusions: The minimum ADC on pretreatment DW-MRI and surgical status on early postoperative MRI can predict survival in patients with GBM. Author Disclosure: R. Murakami: None. H. Nakamura: None. T. Hirai: None. M. Kitajima: None. Y. Nakaguchi: None. S. Nishimura: None. H. Uetani: None. J. Kuratsu: None. Y. Yamashita: None.
2133
Results of Early Reoperation for Suspected Pseudoprogression in Patients with Glioblastoma Multiforme
S. G. Yovino, X. Ye, S. Grossman Johns Hopkins University Sidney Kimmel Cancer Center, Baltimore, MD Purpose/Objective(s): Many patients with glioblastoma multiforme (GBM) develop apparent radiologic progression after standard chemotherapy and radiation. A subset of these patients has no evidence of active tumor at the time of re-operation. We performed a retrospective analysis of patients undergoing reoperation for suspected tumor progression at a single high-volume academic institution. Materials/Methods: Patients were included in this review if the following criteria were fulfilled: 1) diagnosis of GBM; 2) completion of concurrent temozolomide and radiation therapy with or without maintenance temozolomide; 3) surgical re-exploration within one year of completing adjuvant chemoradiation therapy. Patient data were collected by chart review and the protocol was approved by the institutional IRB. Results: From 2005 to 2009, 38 patients with an initial surgical diagnosis of GBM met the above eligibility criteria. At initiation of therapy, median age was 56 years (range, 33 - 80), 55% were male, and 66% had Karnofsky performance status of .90. Median overall survival for the entire cohort of patients was 16.2 months from the time of initial surgery. All reoperations were debulking surgeries rather than needle biopsies and pathology demonstrated that 32% of patients had quiescent tumor or necrosis (95% CI 18 - 49%) and 68% of patients had active GBM. Patients younger than 55 were more likely to have active tumor at the time of reoperation compared with older patients (87% vs 55%, p = 0.03). There was no significant difference in the median time elapsed before second surgery in patients with necrosis/quiescent tumor (8.5 months, 95% CI 6.5 - 10.5 months) compared to those with active GBM (9.2 months, 95% CI 8.1 - 10.3 months). Patients with active tumor at the time of second surgery had a twofold increase in hazard of death (HR 1.95, 95% CI 0.8 - 4.6) using a Cox proportional hazard model adjusted for age, performance status, and extent of resection. Median survival following second surgery was 5 months for patients with active tumor vs. 10 months for patients with quiescent tumor/necrosis. Conclusions: During the first year after diagnosis of GBM over 30% of our patients undergoing a second debulking surgery for radiologic progression had no evidence of active tumor. Time elapsed before reoperation was not a significant factor in determining whether a patient will be found to have pseudoprogression versus recurrent disease. However, pathology at the time of reoperation is an important prognostic factor. It should be noted that 1) patients selected for repeat debulking surgery may not be representative of all GBM patients and 2) pathologic interpretation may vary from institution to institution which could limit the generalizability of this data. Author Disclosure: S.G. Yovino: None. X. Ye: None. S. Grossman: None.
2134
Does the Timing of Radiotherapy Impact Survival of Glioblastoma Multiforme Patients?
E. K. Tezcanli1, A. Ucuncu2, S. Sarihan3, A. Aksu4, C. Eroglu5, G. Alco6, S. Kamer7, M. Ekenel8, S. Aytac Arslan9, U. Abacioglu10, et al. 1 Acibadem University, Department of Radiation Oncology, Istanbul 34742, Turkey, 2Marmara University, Department of Radiation Oncology, Istanbul, Turkey, 3Uludag University Department of Radiation Oncology, Bursa, Turkey, 4Dr. L€utfi Kırdar Kartal Hospital, Radiation Oncology Clinic, Istanbul, Turkey, 5Erciyes University, Department of Radiation Oncology, Erzurum, Turkey, 6Florence Nightingale Hospital, Department of Radiation Oncology, Istanbul, Turkey, 7Ege University, Department of Radiation Oncology, Izmir, Turkey, 8Istanbul University, Oncology Institute, Istanbul, Turkey, 9Dr. Abdurrahman Yurtaslan Ankara Oncology Hospital, Radiation Oncology Clinic, Ankara, Turkey, 10Neolife Medical Center, Istanbul, Turkey
Purpose/Objective(s): The current standard treatment of glioblastoma multiforme (GBM) is maximal safe surgical resection followed by radiotherapy (RT) with concurrent and adjuvant temozolomide (TMZ) chemotherapy; however the
2130
A Feasibility Trial of Concurrent Radiation, Temozolomide, and Bevacizumab Followed by Temozolomide and Bevacizumab for Resectable and Unresectable Glioblastoma Multiforme of the Brain
R. H. Liebross1,2, R. Birhiray2,3, S. Schultz2,4, T. Payner2,5, N. Gupta2,4, R. Young2,5, A. Cohen-Gadol2,5, B. Kuzma2,6, S. Givens1,2, C. Leagre1,2 1 Cancer Care Group, LLC, Indianapolis, IN, 2St. Vincent Hospital, Indianapolis, IN, 3Hematology Oncology of Indiana, Indianapolis, IN, 4American Health Network, Indianapolis, IN, 5Goodman Campbell Brain and Spine, Indianapolis, IN, 6 Northwest Radiology, Indianapolis, IN
Purpose/Objective(s): The use of Bevacizumab (BV) for recurrent high grade gliomas has been promising. We hypothesized based on second line treatment efficacy that incorporating radiation therapy (RT), temozolomide (TMZ) and BV for the primary treatment of glioblastoma multiforme would improve clinical outcomes. The primary objective of this study is to evaluate the median time to progression and secondarily median survival, safety and toxicity. Materials/Methods: Following maximal surgery, if possible, all patients received 61.2 Gy of RT. Concurrently TMZ was given daily (7days/week) at 75 mg/m2 and BV was delivered at 5 mg/kg every 2 weeks. After a 1 month interval upon completion of RT, and MRI of the brain was obtained and the post-RT phase commenced with TMZ at 150 mg/m2 for 5 days every 4 weeks and resumption of BV at 10 mg/kg IV every 2 weeks for a total of 6 months. Results: Thirty-six of 36 enrolled patients have completed protocol therapy. No brain hemorrhages were seen. Five patients developed deep venous thrombosis while on therapy. Three patients had a pulmonary embolism. 5 patients developed neutropenia and 2 of these had pancytopenia. Nine patients had thrombocytopenia. One patient with a history of multiple anal fistulas had a recurrence under treatment. Two patients developed impaired wound healing. The median follow up of patients was 10 months. The median progression free and overall survival were 15 and 16 months, respectively. Conclusions: Early data from treatment with maximal surgery (if possible) followed by RT, TMZ and BV concurrently followed by adjuvant TMZ and BV indicate feasibility. The progression free survival appears promising indicating a potential need for continued maintenance therapy for patients with glioblastoma multiforme. Author Disclosure: R.H. Liebross: None. R. Birhiray: None. S. Schultz: None. T. Payner: None. N. Gupta: None. R. Young: None. A. Cohen-Gadol: None. B. Kuzma: None. S. Givens: None. C. Leagre: None.
2131
MGMT Gene Promoter Methylation Status as a Potent Prognostic Factor in Glioblastoma Treated with Temozolomide Chemo-irradiation
Y. Kim, S. Kim, J. Kim, J. Cho, J. Chang, D. Kim, K. Lee, C. Suh Severance Hospital, Seoul, Korea, Republic of Korea Purpose/Objective(s): The current standard of care for newly diagnosed glioblastoma (GBM) is surgical resection followed by involved-field radiotherapy (RT) with temozolomide (TMZ). Recently, cells that are deficient in O6-methylguanine-DNA methyltransferase (MGMT) have been found to show an increased sensitivity to TMZ, and methylation of the MGMT promoter has been suggested as a predictive marker for GBM. We evaluated whether the methylation status of the MGMT gene promoter affected survival in GBM patients. Materials/Methods: We retrospectively analyzed the cases of 93 patients with histologically confirmed GBM between Jan 2001 and Dec 2008. The patients received post-operative RT with TMZ. The age range was 24-78 yrs (median 58 yrs). Surgical resection was total in 39 patients (42%), subtotal in 30 patients (32%), and partial in 17 patients (18%), while a biopsy only was performed in 7(8%) patients. RT doses ranged from 50-74 Gy (median 70 Gy). The MGMT gene promoter methylation status could be identified in 78 patients; it was unmethylated in 43 patients (55%) and methylated in 35 (45%). In the remaining 15 pts, tissue was not available or the test results were inconclusive. There was no statistically significant difference in terms of clinical characteristics between the methylated and unmethylated MGMT gene promoter groups. Results: All patients were followed-up until death or analyzing time (3-88 months, median 22). Median overall survival was 22 months and progression-free survival was 11 months. The two-year and five-year survival rates were 36% and 15%. MGMT gene promoter methylation status (p = .002) and age (p = .006) were statistically significant prognostic factors for overall survival on both the univariate and multivariate analyses. The median survival for the methylated group was 29 months, and 20 months for the unmethylated group. In 35 pts with methylated MGMT promoter, the two-year and five-year survival rates were 54% and 31%, respectively. Long-term survivors ($ 3-years) were more frequent in the methylated group. (11/35 in methylated group vs 4/43 in unmethylated group). The extent of surgical resection affected progression-free survival. Among the pts who received total or subtotal resections, six pts who were 50 yrs old or younger and showed methylated MGMT, were all alive 38 to 77 months after operation (median 49 months). In contrast, 21 pts who received total or subtotal resections, were older than 50 yrs old, and had unmethylated MGMT, showed only 18 months of median survival. Performance status and RT dose were not significant prognostic factors. Conclusions: In addition to age and extent of surgical resection, MGMT gene promoter methylation status was found to be a potent prognostic factor for GBM, in a study at a single Korean institution. Author Disclosure: Y. Kim: None. S. Kim: None. J. Kim: None. J. Cho: None. J. Chang: None. D. Kim: None. K. Lee: None. C. Suh: None.
2132
Can MRI-derived Factors Predict Survival in Patients with Glioblastoma Multiforme?
R. Murakami1, H. Nakamura2, T. Hirai3, M. Kitajima3, Y. Nakaguchi1, S. Nishimura3, H. Uetani3, J. Kuratsu2, Y. Yamashita3 1 Department of Medical Imaging, Kumamoto University, Kumamoto, Japan, 2Department of Neurosurgery, Kumamoto University, Kumamoto, Japan, 3Department of Diagnostic Radiology, Kumamoto University, Kumamoto, Japan
Purpose/Objective(s): Patients with glioblastoma multiforme (GBM) are usually treated with surgery followed by a combination of radiation therapy (RT) and chemotherapy. Because of the heterogeneous nature of the disease, a large number of factors can
S275
I. J. Radiation Oncology d Biology d Physics
S276
Volume 81, Number 2, Supplement, 2011
potentially influence the prognosis. Furthermore, advanced diagnostic and therapeutic developments may provide novel prognostic factors. As a pretreatment variable, diffusion-weighted (DW) magnetic resonance imaging (MRI) with quantitative apparent diffusion coefficient (ADC) can be a clinical biomarker. Many neurosurgeons advocate tumor resection as extensive as possible and early postoperative MRI within 72 hr after surgery is thought to reliably detect residual tumors. The purpose of this study was to determine which factors can predict survival more convincingly in patients with GBM. Materials/Methods: Between January 2000 and September 2009, 138 patients with GBM underwent postoperative RT and longitudinal MRI preoperatively, in the early postoperative period, and at 1-month intervals thereafter until recurrence. On early postoperative MRI, the surgical status was classified into biopsy, partial resection (PR), and gross total resection (GTR). Patient age, Karnofsky performance scale (KPS) score, minimum ADC, and surgical status were assessed by factor analysis of overall survival (OS). Radiation therapy oncology group-recursive partitioning analysis (RTOG-RPA) criteria were used to validate prognostic values of the MRI-derived factors, i.e., minimum ADC and surgical status. Kaplan-Meier survival curves, the log-rank test, and the multivariate Cox proportional hazards model were used to evaluate the prognostic factors. Results: Median OS associated with low (\ 0.9310 3 mm2/sec) and high ($ 0.9310 3 mm2/sec) minimum ADC was 11.2 and 18.0 months, respectively (p \ 0.001). According to surgical status, median OS associated with biopsy or PR and GTR was 11.7 and 18.9 months, respectively (p\0.001). Substantial independent prognostic factors were KPS score (hazard ratio = 1.812; 95% confidence interval (CI), 1.185-2.771), minimum ADC (2.365; 95% CI, 1.482-3.776), and surgical status (1.777; 95% CI, 1.073-2.943). The MRI-derived factors assigned patients to different prognostic groups in RTOG-RPA classes and stratified into high risk of low minimum ADCs with residual tumors, low risk of high minimum ADCs without residual tumors, and intermediate risk of the others. Median OS among low, intermediate, and high risk group was 28.2, 14.7, and 10.8 months, respectively (p \ 0.001). Conclusions: The minimum ADC on pretreatment DW-MRI and surgical status on early postoperative MRI can predict survival in patients with GBM. Author Disclosure: R. Murakami: None. H. Nakamura: None. T. Hirai: None. M. Kitajima: None. Y. Nakaguchi: None. S. Nishimura: None. H. Uetani: None. J. Kuratsu: None. Y. Yamashita: None.
2133
Results of Early Reoperation for Suspected Pseudoprogression in Patients with Glioblastoma Multiforme
S. G. Yovino, X. Ye, S. Grossman Johns Hopkins University Sidney Kimmel Cancer Center, Baltimore, MD Purpose/Objective(s): Many patients with glioblastoma multiforme (GBM) develop apparent radiologic progression after standard chemotherapy and radiation. A subset of these patients has no evidence of active tumor at the time of re-operation. We performed a retrospective analysis of patients undergoing reoperation for suspected tumor progression at a single high-volume academic institution. Materials/Methods: Patients were included in this review if the following criteria were fulfilled: 1) diagnosis of GBM; 2) completion of concurrent temozolomide and radiation therapy with or without maintenance temozolomide; 3) surgical re-exploration within one year of completing adjuvant chemoradiation therapy. Patient data were collected by chart review and the protocol was approved by the institutional IRB. Results: From 2005 to 2009, 38 patients with an initial surgical diagnosis of GBM met the above eligibility criteria. At initiation of therapy, median age was 56 years (range, 33 - 80), 55% were male, and 66% had Karnofsky performance status of .90. Median overall survival for the entire cohort of patients was 16.2 months from the time of initial surgery. All reoperations were debulking surgeries rather than needle biopsies and pathology demonstrated that 32% of patients had quiescent tumor or necrosis (95% CI 18 - 49%) and 68% of patients had active GBM. Patients younger than 55 were more likely to have active tumor at the time of reoperation compared with older patients (87% vs 55%, p = 0.03). There was no significant difference in the median time elapsed before second surgery in patients with necrosis/quiescent tumor (8.5 months, 95% CI 6.5 - 10.5 months) compared to those with active GBM (9.2 months, 95% CI 8.1 - 10.3 months). Patients with active tumor at the time of second surgery had a twofold increase in hazard of death (HR 1.95, 95% CI 0.8 - 4.6) using a Cox proportional hazard model adjusted for age, performance status, and extent of resection. Median survival following second surgery was 5 months for patients with active tumor vs. 10 months for patients with quiescent tumor/necrosis. Conclusions: During the first year after diagnosis of GBM over 30% of our patients undergoing a second debulking surgery for radiologic progression had no evidence of active tumor. Time elapsed before reoperation was not a significant factor in determining whether a patient will be found to have pseudoprogression versus recurrent disease. However, pathology at the time of reoperation is an important prognostic factor. It should be noted that 1) patients selected for repeat debulking surgery may not be representative of all GBM patients and 2) pathologic interpretation may vary from institution to institution which could limit the generalizability of this data. Author Disclosure: S.G. Yovino: None. X. Ye: None. S. Grossman: None.
2134
Does the Timing of Radiotherapy Impact Survival of Glioblastoma Multiforme Patients?
E. K. Tezcanli1, A. Ucuncu2, S. Sarihan3, A. Aksu4, C. Eroglu5, G. Alco6, S. Kamer7, M. Ekenel8, S. Aytac Arslan9, U. Abacioglu10, et al. 1 Acibadem University, Department of Radiation Oncology, Istanbul 34742, Turkey, 2Marmara University, Department of Radiation Oncology, Istanbul, Turkey, 3Uludag University Department of Radiation Oncology, Bursa, Turkey, 4Dr. L€utfi Kırdar Kartal Hospital, Radiation Oncology Clinic, Istanbul, Turkey, 5Erciyes University, Department of Radiation Oncology, Erzurum, Turkey, 6Florence Nightingale Hospital, Department of Radiation Oncology, Istanbul, Turkey, 7Ege University, Department of Radiation Oncology, Izmir, Turkey, 8Istanbul University, Oncology Institute, Istanbul, Turkey, 9Dr. Abdurrahman Yurtaslan Ankara Oncology Hospital, Radiation Oncology Clinic, Ankara, Turkey, 10Neolife Medical Center, Istanbul, Turkey
Purpose/Objective(s): The current standard treatment of glioblastoma multiforme (GBM) is maximal safe surgical resection followed by radiotherapy (RT) with concurrent and adjuvant temozolomide (TMZ) chemotherapy; however the