Long Duration of Response Seen for Pembrolizumab in Endometrial Cancer

David O’Malley, MD, a professor in the department of obstetrics and gynecology at The Ohio State University College of Medicine and the director of the division of gynecologic oncology at the OSUCCC–James, discusses the background and updated results of the KEYNOTE-158 trial (NCT02628067) looking at pembrolizumab (Keytruda) monotherapy in patients with advanced endometrial cancer.

The phase 2 KEYNOTE-158 investigated pembrolizumab in patients with advanced solid tumors and microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) status. In patients with endometrial cancer, at a median follow-up of 42.8 months, there was an objective response rate (ORR) of 48% (95% CI, 37%-60%).

In updated results presented at the 2022 European Society for Medical Oncology Congress, there was a median time from first dose to data cutoff (January 12, 2022) of 54.5 months (range, 14.7-71.4). The ORR was 50% and median duration of response was 63.2 months (range, 2.9-63.2). At the data cutoff, out of 94 patients, 22 patients (23.4%) had completed therapy, 67 (71.3%) had discontinued therapy, and 5 (5.3%) remained on pembrolizumab treatment. According to O’Malley, the estimated rate of a DOR of at least 4 years with pembrolizumab was 66%.

TRANSCRIPTION:

0:08 | We presented updated long-term follow-up results of KEYNOTE-158. Recently, we published the results in the Journal of Clinical Oncology, which showed approximately 50% ORR with patients doing very well for long term and continuing the duration of response. That trial actually contributed to extending the approval of pembrolizumab, specifically to endometrial cancer for pembrolizumab in patients who [have] MSI-high or dMMR endometrial cancer.

The updated results that we presented are looking at longer-term follow-up. We had approximately 55 months of median follow-up with our patients and we show that the ORR is 50%. With that 50% ORR, we actually had two-thirds of patients [who] extended for 4 years or more of duration of response.