ESMO 2021: Update From KEYNOTE-355 on Pembrolizumab Plus Chemotherapy in Triple-Negative Breast Cancer
Posted: Wednesday, September 29, 2021
Hope S. Rugo, MD, of the University of California San Francisco Comprehensive Cancer Center, and colleagues presented their final results of the KEYNOTE-355 trial of first-line pembrolizumab plus chemotherapy versus placebo plus chemotherapy in metastatic triple-negative breast cancer during the European Society for Medical Oncology (ESMO) Congress 2021 (Abstract LBA16). Previous analyses of this study showed improved progression-free survival with pembrolizumab versus placebo, and these phase II results demonstrated a statistically significant improvement in overall survival with the addition of pembrolizumab, with no new safety signals.
A total of 847 patients with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer were enrolled. Participants were randomly assigned 2:1 to receive nab-paclitaxel, paclitaxel, or gemcitabine/carboplatin chemotherapy plus either pembrolizumab (n = 566) or a placebo (n = 281). Treatment was continued until disease progression or intolerable toxicity, and patients were stratified by chemotherapy type, PD-L1 status (Combined Positive Score [CPS]), and prior treatment.
The median follow-up was 44.1 months. There was an observed improvement in overall survival (17.2 vs. 15.5 months) and progression-free survival (7.5 vs. 5.6 months) for those given pembrolizumab versus placebo in the intent-to-treat population. Notably, patients given pembrolizumab who had a CPS score of 10 or greater experienced significantly better overall survival and progression-free survival than those receiving the placebo.
The addition of pembrolizumab to chemotherapy yielded a progression-free survival that was consistent with previous study results. Additionally, this combination improved the objective response rate among the intent-to-treat population (40.8% vs. 37.0%), and it was significantly improved in patients with a CPS score of 10 or greater (52.7% vs. 40.8%). However, treatment-related adverse events of grades 3 to 5 were observed at similar rates among both groups, affecting 68.1% of individuals treated with pembrolizumab plus chemotherapy and 66.9% of those treated with chemotherapy plus placebo.
Disclosure: For full disclosures of the study authors, visit oncologypro.esmo.org.
