For the first time, an international study shows that adding immunotherapy to chemotherapy can significantly extend the lives of patients affected by a form of ovarian cancer that has previously had no solution.
Platinum-resistant ovarian cancer, a fight against therapeutic exhaustion
Long silent, often diagnosed at an advanced stage, ovarian cancer is one of the most formidable among gynecological cancers. In some women, the disease returns very quickly after standard platinum-based treatments. We then talk about platinum-resistant ovarian cancer – a particularly aggressive form, difficult to treat, where the chances of lasting remission diminish with relapses.
In this context, medicine seemed to have reached its limits. After several lines of chemotherapy, the tumor resisted, the response time shortened, and the prospects narrowed. So, for these patients, each new research represents more than a statistic: a fragile but vital promise.
It is in this spirit that the KEYNOTE-B96/ENGOT-ov65 study was born, presented at the ESMO 2025 congress. It explores a long-awaited avenue: that of immunotherapy, already used in other cancers, but whose benefits have never before been clearly demonstrated in this particular form of ovarian cancer.
A game-changing study: pembrolizumab improves survival
The test, conducted with 643 patients worldwide, compared two treatments: on the one hand, weekly chemotherapy with paclitaxel, sometimes combined with bevacizumab; on the other, the same chemotherapy accompanied by pembrolizumab (Keytruda)an immunotherapy drug developed by Merck. The objective was simple but crucial: to find out if this combination could offer a few additional months of life, or better yet, better control of the disease.
The results were surprising in their solidity. After a median follow-up of more than two years, the overall survival of patients whose tumor expressed the PD-L1 protein (the biomarker targeted by pembrolizumab) went from 14 to 18.2 months. There progression-free survival – the time during which the disease does not worsen – has also become longer, 6.4 to 8.3 months on average.
These gaps, modest on paper, take on immense meaning in the reality of these women, where each month gained is a victory over the inevitable.
When presenting these results at the cancer conference, British researcher Rebecca Kristeleit from King’s College London estimated that: “These data are very interesting and could change the way we think about the use of immunotherapy in this cancer, because it is the first time that we have observed a positive signal on overall survival with an immune checkpoint inhibitor, all forms combined..
Same enthusiasm from the Italian professor Nicoletta Colombo, director of the gynecological oncology program at the European Institute of Oncology in Milan and main author of the study, who underlines the clinical importance of the result: “The survival observed is among the longest ever reported in a clinical trial for this type of cancer, proving a real and significant benefit for patients..
Beyond the figures, these comments reflect a rare feeling in this field: that of tangible, almost unexpected progress, after years of therapeutic stagnation.
A promising but still fragile step forward
While this study represents a major breakthrough, it does not solve everything. The improvement in survival remains moderate, and high-grade side effects were observed in more than two thirds of patients. However, the benefit-risk ratio remains considered “manageable” by the investigators.
One essential question remains: Which patients will benefit the most from this strategy? As Rebecca Kristeleit explains: “It will be important to analyze the influence of factors such as tumor type, mode of recurrence and certain biological markers such as mismatch repair or mutational load.”. These parameters could, ultimately, help doctors to better target those for whom immunotherapy will bring real benefit. Regulatory authorities may even request these details if they consider that for an unselected population, the clinical benefit remains too modest in relation to the side effects.
Other avenues are already emerging: drug-conjugated antibodiesthese new generation treatments capable of directly delivering chemotherapy to the heart of tumor cells, could be tested in combination with pembrolizumab and/or bevacizumab in this disease.