Benefit of adjuvant pembrolizumab in endometrial cancer varies by mismatch repair status
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Key takeaways:
- Results showed a DFS benefit with the addition of pembrolizumab to chemotherapy for patients with mismatch repair-deficient tumors.
- The rate of grade 3 or greater adverse events was slightly higher with pembrolizumab.
The addition of pembrolizumab to adjuvant chemotherapy improved DFS for certain women with newly diagnosed high-risk endometrial cancer, according to randomized phase 3 study results presented at ESMO Congress.
The benefit appeared limited to women with mismatch repair-deficient tumors. Results showed no benefit in the overall study population.
Prior studies showed the addition of the anti-PD-1 antibody pembrolizumab (Keytruda, Merck) to chemotherapy conferred benefit as first-line treatment for women with advanced or recurrent endometrial cancer regardless of mismatch repair (MMR) status, according to study background.
Researchers conducted the KEYNOTE-B-21 study to assess the efficacy of adding pembrolizumab to adjuvant chemotherapy for women with newly diagnosed, high-risk endometrial cancer who underwent surgery with curative intent.
The trial included 1,095 women with newly diagnosed, histologically confirmed high-risk endometrial l cancer who had no evidence of disease after curative-intent surgery.
Trial protocol excluded women who received prior radiation therapy or systemic therapy.
Researchers assigned 545 women to 200 mg pembrolizumab every 3 weeks for 6 cycles plus carboplatin-paclitaxel, followed by 400 mg pembrolizumab once every 6 weeks for six cycles. The other 550 women received placebo plus carboplatin-paclitaxel, followed by placebo.
DFS per investigator assessment and OS in the intent-to-treat population served as the primary endpoints.
At the time of interim analysis, 119 (22%) DFS events had occurred in the pembrolizumab group and 121 (22%) had occurred in the placebo group (HR = 1.02; 95% CI, 0.79-1.32).
In the overall population, 2-year DFS appeared comparable between the pembrolizumab and placebo groups (75% vs. 76%).
However, subgroup analysis revealed significantly improved DFS for women with MMR-deficient tumors (HR = 0.31; 95% CI, 0.14-0.69), compared with no benefit for women with MMR-proficient tumors (HR = 1.2; 95% CI, 0.91-1.57).
A higher percentage of women assigned pembrolizumab experienced grade 3 or higher adverse events (71% vs. 63%). No treatment-related grade 5 events occurred.
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Van Gorp T, et al. Abstract LBA28. Presented at: European Society for Medical Oncology Congress; Sept. 13-17; Barcelona, Spain.
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