Atezolizumab Combined With Bevacizumab and Platinum-Based Therapy for Platinum-Sensitive Ovarian Cancer: Placebo-Controlled Randomized Phase III ATALANTE/ENGOT-ov29 Trial.

Platinum-based doublets with concurrent and maintenance bevacizumab are standard therapy for ovarian cancer (OC) relapsing after a platinum-free interval (PFI) >6 months. Immunotherapy may be synergistic with bevacizumab and chemotherapy. ATALANTE/ENGOT-ov29 (ClinicalTrials.gov identifier: NCT02891824), a placebo-controlled double-blinded randomized phase III trial, enrolled patients with recurrent epithelial OC, one to two previous chemotherapy lines, and PFI >6 months. Eligible patients were randomly assigned 2:1 to atezolizumab (1,200 mg once every 3 weeks or equivalent) or placebo for up to 24 months, combined with bevacizumab and six cycles of chemotherapy doublet, stratified by PFI, PD-L1 status, and chemotherapy regimen. Coprimary end points were investigator-assessed progression-free survival (PFS) in the intention-to-treat (ITT) and PD-L1-positive populations (alpha .025 for each population). Between September 2016 and October 2019, 614 patients were randomly assigned: 410 to atezolizumab and 204 to placebo. Only 38% had PD-L1-positive tumors. After 3 years' median follow-up, the PFS difference between atezolizumab and placebo did not reach statistical significance in the ITT (hazard ratio [HR], 0.83; 95% CI, 0.69 to 0.99; ATALANTE/ENGOT-ov29 did not meet its coprimary PFS objectives in the ITT or PD-L1-positive populations. OS follow-up continues. Further research on biopsy samples is warranted to decipher the immunologic landscape of late-relapsing OC.