Bevacizumab plus fosbretabulin in recurrent ovarian cancer: Overall survival and exploratory analyses of a randomized phase II NRG oncology/gynecologic oncology group study

Objective: To explore the relationship between tumor size and response to combined anti-vascular targeted therapy using the anti-angiogenesis inhibitor, bevacizumab, and the tubulin-binding vascular disrupting agent, fosbretabulin.

Methods: An exploratory, post-hoc analysis of the randomized phase II trial, Gynecologic Oncology Group-0186I, was performed. One hundred and seven patients with recurrent ovarian carcinoma, treated with up to 3 prior regimens, were randomized to bevacizumab 15 mg/kg body weight with or without intravenous fosbretabulin 60 mg/m2 body surface area every 21 days until progression or unacceptable toxicity. The primary analysis favored the combination (HR 0.69; 95% CI, 0.47-1.00; p = .049) [Monk BJ, et al. J Clin Oncol 2016;34:2279-86]. The Cox proportional hazards model was used to estimate the treatment effect in various subpopulations.

Results: With extended follow-up, the median PFS for bevacizumab plus fosbretabulin was 7.6 months as compared to 4.8 months with bevacizumab alone (HR 0.74; 90% CI, 0.54-1.02). Overall survival was similar in the experimental and control arms (25.2 vs 24.4 mos, respectively, HR 0.85; 90% CI, 0.59-1.22; p = .461). Eighty-one patients had measurable disease and median tumor size was 5.7 cm. In the ≤5.7 cm subgroup, the HR for progression or death was 0.77 (90% CI 0.45-1.31). Patients with tumors >5.7 cm (n = 40) had a HR for progression or death of 0.55; 90% CI, 0.32-0.96; p = .075).

Conclusions: Although no significant survival benefit was observed, the trend showing a reduced HR for progression or death with increasing tumor size when fosbretabulin is added to bevacizumab compared to bevacizumab alone warrants further study.

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S7204 Fosbretabulin (Combretastatin A4 Phosphate (CA4P)) Disodium Fosbretabulin (Combretastatin A4 Phosphate, CA4P, CA 4DP) Disodium is the water-soluble prodrug of Combretastatin A4 (CA4), which is a microtubule-targeting agent that binds β-tubulin with Kd of 0.4 μM in a cell-free assay. Fosbretabulin Disodium inhibits the polymerization of tubulin with IC50 of 2.4 μM, and also disrupts tumor vasculature. Fosbretabulin disodium induces mitotic arrest and apoptosis in endothelial cells. Phase 3.

Related Targets

Apoptosis related Microtubule Associated