A new study shows that adding the immunotherapy drug pembrolizumab (Keytruda) to standard chemotherapy may help some people with advanced ovarian cancer live longer. The findings, from the phase 3 ENGOT-ov65/KEYNOTE-B96 trial, offer new hope for patients whose cancer has stopped responding to platinum-based treatments—a group for whom options remain very limited.
Presented at the ESMO Congress 2025 in Berlin, the study tested pembrolizumab combined with weekly paclitaxel (a type of chemotherapy), with or without the addition of bevacizumab (Avastin), in 643 patients with platinum-resistant ovarian cancer.
Longer Survival With Pembrolizumab
After more than two years of follow-up, researchers found that patients whose tumors tested positive for PD-L1—a protein that may indicate responsiveness to immunotherapy—lived an average of 18.2 months with the pembrolizumab-based treatment compared to 14.0 months with standard therapy. Progression-free survival, or the length of time before the cancer worsened, also improved modestly: 8.3 months versus 6.4 months overall.
Why the Findings Matter
Patients with platinum-resistant ovarian cancer often face limited options and poor outcomes. Historically, chemotherapy regimens like weekly paclitaxel—sometimes paired with bevacizumab—offered modest control but rarely extended life substantially.
This trial marks the first time immunotherapy has significantly improved overall survival for this group, suggesting that pembrolizumab-based combinations could become a new treatment option for certain patients.
Safety and Future Directions
Side effects were generally manageable, though severe treatment-related events occurred somewhat more often with pembrolizumab than without (about two-thirds of patients versus just over half).
Researchers also noted that future studies should explore which patients are most likely to benefit, including those with specific tumor characteristics or rare ovarian cancer subtypes.
What This Means for Patients
If your ovarian cancer has stopped responding to platinum-based treatment, this research offers a new reason for hope. Adding pembrolizumab (an immunotherapy) to weekly paclitaxel, with or without bevacizumab, may help some patients live longer and keep the cancer from growing as quickly.
While the improvements in time without progression are modest, the overall survival benefit is significant for this stage of disease. The combination treatment may soon become an option for women with PD-L1–positive tumors, once approved and available beyond clinical trial settings.
Patients should talk with their oncologist about whether immunotherapy or clinical trials exploring pembrolizumab combinations could be appropriate for their situation.
Reference
Colombo N, et al. Pembrolizumab vs placebo plus weekly paclitaxel ± bevacizumab in platinum-resistant recurrent ovarian cancer: results from the randomized double-blind phase 3 ENGOT-ov65/KEYNOTE-B96 study. ESMO Congress 2025 – LBA3
