Immunotherapy in endometrial cancer: who are the most appropriate patients?

In an exciting milestone for endometrial cancer therapeutics, Ott et al. recently published the results from the KEYNOTE-028 study in the Journal of Clinical Oncology (1). This Phase Ib clinical trial was part of a larger set of basket trial expansion cohorts evaluating the safety and preliminary efficacy of pembrolizumab treatment in 20 solid tumor types with PD-L1 positivity. In this study, PD-L1 positivity was defined as staining of the membrane in at least 1% of the tumor and related inflammatory cells, or positive staining noted in the stroma. The authors found that 3 of the 23 patients evaluated for treatment response demonstrated partial responses, and an additional 3 patients had stable disease. All 3 patients with partial responses had durable responses lasting longer than 60 weeks. The other important finding was that of the 75 patients with advanced endometrial cancer who were screened, 36 (48%) had tumors demonstrating PD-L1 positivity.