P11.76.A Retrospective evaluation of Overall Survival and Progression Free Survival in patients with glioblastoma comparing 6 vs 12 cycles of Adjuvant Temozolomide

Abstract Background The standard of care for glioblastoma multiforme (GBM) is surgery followed by adjuvant concomitant chemo-radiotherapy and adjuvant temolomide (TMZ) for 6 cycles. Extending the duration of adjuvant TMZ did not demonstrate an overall survival (OS) benefit in a meta-analysis including 2214 GBM patients. A phase II randomized clinical trial including 166 GBM patients compared 6 vs 12 cycles of TMZ, showing no differences in progression-free-survival (PFS), although MGMT methylated patients showed better outcomes. The objective of this study is to analyze PFS and OS of GMB patients receiving 6 vs 12 cycles of adjuvant TMZ. Material and Methods Patients with a pathological diagnosis of GBM between 1 December 2016 and 31 December 2020 in a single center (Hospital Universitario La Paz) were retrospectively reviewed. Inclusion criteria were confirmed pathological diagnosis and patients receiving multimodality treatment (surgery, radiation and chemotherapy). Two cohorts were analyzed, cohort A patients receiving 6 cycles of adjuvant TMZ and cohort B patients receiving 12 cycles of adjuvant TMZ. Statistical analysis was performed via SPSS v.21 (differences between both cohorts were calculated using χ² and T Student and survival outcomes with Kaplan Meier curves, comparing its differences using log-rank test). Results Sixty-eight patients were included in the final analysis, with a median age of 58 years at diagnosis. Fourty-two patients (62%) received 6 cycles of adjuvant TMZ (cohort A), whereas 26 patients (38%) received 12 cycles (cohort B). Median OS was 10 months for cohort A and 20 months for cohort B (p<0,001), median PFS was 8 months for cohort A and 19 months for cohort B (p=0,001). No significant differences were shown between both cohorts regarding age at diagnosis, being 60 years in cohort A and 54 years in cohort B (p = 0,06), and positive-margins after surgery (p=0,796), being 9,5% and 7,7% respectively in each cohort. Significant differences were found regarding MGMT methylation (30% in cohort A and 68% in cohort B). Conclusion In our study, patients receiving 12 cycles of adjuvant TMZ had better median OS and median PFS, compared to patients receiving 6 cycles, although the latter group had significantly less MGMT methylated patients, which is a known prognostic and predictive factor of response to TMZ.