P14.15 Benefit of Bevacizumab for recurrent glioblastoma. Results of 81 patients from a single institution

Abstract BACKGROUND No standard of care has been established for patients with progressive glioblastoma (rGBM). Previous studies suggested that bevacizumab (BEV) is safe and produces responses that result in a decreased use of glucocorticoids and increased progression-free survival (PFS) with an unclear effect on overall survival (OS). Crossover to BEV in the control arm is the possible reason why the advantage of BEV has not been proven in Phase III trials. We retrospectively analyzed own results of BEV treatment in rGBM. MATERIAL AND METHODS 81 patients progressed after radiotherapy plus concomitant and maintenance temozolomide (TMZ) and undergo BEV as monotherapy (BevMo, 11 patients) or in combinations (Irinotecan (BevI) - 53, lomustine (BevL)- 11, TMZ (BevT) - 6. Median age 54 years. Among them 33 patients were re-irradiated: 11 - radiosurgery (RS), 20 fractionated irradiation (RT), 2 - RS+RT. 33 patients continued BEV after progression with changing or adding cytostatic. PFS was calculated from the date of verification, PFS1 - from the date of 1-st progression, PFS2 - from the date of 2-nd progression. RESULTS Median PFS was 9.0 ([CI] 7.0–10.9) months. Median PFS1 was 10.5 ([CI] 8.1–12.9) months. In the BevMo, BevI, BevL, BevT group PFS1 was 15.7, 10.1, 10.5, 13.2 months, respectively, p=0.7. Objective response (OR) was reached in 34%, stable disease (SD) in 28%, progression (PD) in 37% patients. 16 patients stopped BEV without progression (4-patient`s decision, 7- doctor`s decision, 2 - adverse event, 3 - concomitant disease). Median time of BEV treatment was 11.6 months. Median BEV-free interval till progression was 3.7 months. 33 patients continued or restarted BEV after progression. Median PFS2 was 8.0 ([CI] 4.9–11.1) months. The median OS from the date of 1-st progression was 23.5 months ([CI] 18.7–27.4). In groups with RT, RS, RS+RT and no re-irradiarion OS was 24.6 ([CI] 17.6–31.5), 35.4 ([CI] 35.0–35.8), 17.8, 20.6 ([CI] 15.2–26.0), respectively, p=0.2. CONCLUSION OS in our group is outrageously high. Maintaining BEV after progression was effective. In our group BEV discontinuation led to rapid progression. The resumption of Bev with progression was effective, which indicates the advisability of its continuous application.