Retrospective analysis of patients of glioblastoma multiforme treated with stem cell sparing intensity-modulated radiation therapy and nonstem cell sparing three-dimensional conformal radiation therapy: A single-institution experience

Aims: The present study was aimed to assess the impact of stem cell sparing radiation therapy on the outcomes of the treatment in glioblastoma multiforme (GBM). Materials and Methods: The present retrospective study was done in the Advanced Center of Radiation Oncology Department of Nanavati Super Speciality Hospital, Mumbai. All case files from 2010 to 2016 having confirmed diagnoses of GBM were retrieved for assessment. Totally 46 patients were included in the study and divided in intensity-modulated radiation therapy (IMRT) group and non-IMRT (three-dimensional conformal radiation therapy [3DCRT]) group. Twenty-eight patients received IMRT and 18 patients received non-IMRT (3DCRT). All patients receive total dose of 60 Gray (Gy) in 6 weeks and 30 fractions after tumor resection with temozolomide. Results: It has been observed that the mean age was 58.5 years in IMRT group and 54.4 years in non-IMRT group. Gross-total resection or near-total resection was performed in 7 (25%) of patients in IMRT group while it was 4 (22.2%) patients in non-IMRT group. Four patients in each group had only biopsy, while rest of them underwent subtotal resection. The mean dose to contralateral subventricular zone (SVZ) was 27.96 Gy in IMRT group and 32.60 Gy in non-IMRT group while dose received by ipsilateral SVZ was 47.19 Gy and 48.53 Gy in IMRT and non-IMRT group, respectively. Maximum dose to contralateral and ipsilateral SVZ was 49.29 and 59.53 Gy in IMRT group. Similarly, in non-IMRT group, dose to contralateral and ipsilateral SVZ was 45.5 and 59.14 Gy, respectively. The minimum dose received by contralateral SVZ was 9.1 Gy in IMRT group and 19.45 Gy in non-IMRT group while dose received by ipsilateral SVZ was 19.87 and 35.3 Gy in IMRT and non-IMRT group, respectively. The mean volume of contralateral SVZ was 7.68 and 6.62 cc, respectively. There is no statistically significant difference between both the groups for the mean dose to SVZ. The overall survival in both the groups was 19.22 months and median follow-up was 22.27 months. There is no difference in survival between both the groups (P = 0.66). A Kaplan Meier curves were generated using the facility in STATA 14.2. A cursory examination of the two curves, one each for IMRT and 3DCRT shows differences between the two treatments. However, the significance test, log-rank test, indicates otherwise. The chi-square of the test is 1.67 and the Pr > χ2 = 0.1960. Hence, the hypothesis that the survival from the two treatments do not significantly differ, cannot be rejected. Conclusion: Our retrospective analysis demonstrates no difference in overall survival between both groups. Hence, there was no impact of sparing stem cell on survival in GBM