Findings from the international phase II KEYNOTE-158 trial of pembrolizumab among women with previously treated microsatellite instability–high (MSI-H) or mismatch repair–deficient (dMMR) endometrial tumors “suggest a long-term benefit to patients,” stated the trial’s lead author David M. O’Malley, MD, of The Ohio State University Wexner Medical Center and The James Comprehensive Cancer Center, Columbus. “Thepotential for curative intent may now be possible in patients with recurrent or metastatic uterine cancer.”

In an interview with The ASCO Post, Dr. O’Malley pointed out that the duration-of-response curve in the report published in the Journal of Clinical Oncology showed “that if you get a response, the chance that your response lasts 3 years is 68%.” Although he tempered his remarks, noting that he was being careful not to overstate the results, he nevertheless commented: “This is amazing. These outcomes are unprecedented in the treatment of uterine endometrial cancer.”

‘Particularly Encouraging’

The study findings “are particularly encouraging in light of the low long-term survival rates typically observed in advanced endometrial cancer,” according to the published paper. “Standard-of-care first-line systemic therapy for patients with advanced or recurrent endometrial cancer commonly comprises a platinum-based chemotherapy regimen such as carboplatin plus paclitaxel,” the researchers wrote. “However, treatment options after disease progression with first-line therapy are limited. For patients with advanced or recurrent endometrial cancer, 5-year survival rates of approximately 20% have been reported.”

In the current study, median overall survival was not reached, but it was estimated to be “69% at 1 year and 64% at 2 years, with a plateau at 60% at 3 and 4 years,” the authors reported.