Patients with triple-negative breast cancer (TNBC) that has metastasized to the lung or liver saw no significant overall survival benefit when treated with pembrolizumab monotherapy compared with single-agent chemotherapy, according to the results of a retrospective analysis of the KEYNOTE-119 trial (ClinicalTrials.gov Identifier: NCT02555657).
These results are consistent with the global population of the trial, Eric Winer, MD, of Dana-Farber Cancer Institute, Boston, Massachusetts, and colleagues wrote in a poster presented at the 2020 Virtual San Antonio Breast Cancer Symposium (SABCS).
KEYNOTE-119 was a phase 3 trial that randomly assigned 622 women with metastatic TNBC to receive pembrolizumab monotherapy or single-agent chemotherapy. Results showed that there was improvement in overall survival with pembrolizumab, but it was not statistically significant. In this retrospective analysis, the researchers explored if the efficacy of pembrolizumab varied by location of metastasis.
Of the included patients, 65% had lung metastasis and 28% had liver metastasis. In the intention-to-treat population, pembrolizumab did not improve overall survival compared with chemotherapy (lung hazard ratio [HR], 0.99; 95% CI 0.80-1.23; liver HR, 1.04; 95% CI, 0.76-1.43).
However, the hazard ratios decreased as tumor programmed cell death ligand 1 (PD-L1) expression increased, with those patients with a combined positive score (CPS) of 20 or higher seeing the most benefit from the drug (lung HR, 0.53 95% CI, 0.31-0.92; liver HR, 0.65 95% CI, 0.31-1.38).
The researchers noted similar trends for progression-free survival.
The objective response rates (ORR) in patients with lung metastasis were 9% for pembrolizumab compared with 8% for chemotherapy. In patients with liver metastasis, the ORR was 7% for pembrolizumab and 10% for chemotherapy. Median duration of response was not significantly different between the arms.
“Although results should be interpreted with caution due to modest sample size in some subgroups, findings may inform further research of pembrolizumab for patients with previously treated PD-L1–enriched TNBC with lung or liver metastasis; populations in whom prognosis is typically poor,” the researchers wrote.
Winer E, et al. Pembrolizumab versus chemotherapy for previously treated metastatic triple-negative breast cancer (KEYNOTE-119): efficacy in patients with lung or liver metastases. Presented at: 2020 Virtual San Antonio Breast Cancer Symposium (SABCS); December 8-11, 2020. Abstract PS12-01.