Impact of adding the immune checkpoint inhibitor atezolizumab to first-line chemotherapy on progression-free survival in poor-prognosis ovarian cancer: A retrospective analysis from the IMagyn050 trial.

Purpose: Adding the anti-PD-L1 antibody atezolizumab to frontline chemotherapy-bevacizumab regimen did not improve progression-free survival (PFS) in ovarian cancer (OC) patients in IMagyn050 trial. This post-hoc analysis assessed the efficacy of atezolizumab in a subgroup of patients with particularly poor prognosis, as defined by the GCIG meta-analysis-characterized by a poor chemosensitivity and a suboptimal surgical resection.

Methodology: This analysis included 1199 evaluable participants with ≥3 available CA-125 concentrations, as required for KELIM score. The prognostic factors were identified through univariable and multivariable analyses. If both the KELIM score (unfavorable <1.0, vs favorable ≥1.0) and surgical outcome (suboptimal, vs optimal resection) demonstrated independent prognostic value, they were to be combined into prognostic subgroups. The PFS benefit of atezolizumab versus placebo was then evaluated within each of these defined subgroups.

Results: Both the KELIM score and surgical outcome were independent prognostic factors. Combining these two parameters generated three distinct prognostic subgroups. In the poor prognosis subgroup (n = 269), defined by both an unfavorable KELIM score (<1.0) and suboptimal cytoreduction, the addition of atezolizumab was associated with a significantly longer median PFS compared to placebo (14.3 vs 11.3 months; HR 0.75, 95 % CI 0.59-0.95). This benefit was observed in both neoadjuvant and adjuvant settings. No significant PFS benefit was observed in the other prognostic subgroups.

Conclusion: The poor prognostic OC patient subgroup, may have an extension of PFS from treatment intensification with atezolizumab added to frontline chemotherapy-bevacizumab regimen. This hypothesis-generating outcome warrants further understanding on the added role of ICI in the frontline setting.