SABCS 2021: KEYNOTE-355 Final Results of Pembrolizumab Plus Chemotherapy in Triple-Negative Breast Cancer
Posted: Tuesday, December 14, 2021
The phase III KEYNOTE-355 study, which evaluated pembrolizumab plus chemotherapy versus chemotherapy alone in patients with previously untreated, locally recurrent, inoperable or metastatic triple-negative breast cancer, was conducted by Javier Cortes, MD, PhD, of the International Breast Cancer Center, Madrid, and colleagues. Presented during the 2021 San Antonio Breast Cancer Symposium (SABCS; Abstract GS1-02), their final results demonstrated that the addition of pembrolizumab yielded significant survival improvements over placebo and suggest that a combined positive score (CPS) of at least 10 is a “reasonable” cutoff to determine expected treatment benefit.
The investigators focused on 847 patients with previously untreated, locally recurrent, inoperable or metastatic triple-negative breast cancer. Participants were randomly assigned to receive nab-paclitacel, paclitaxel, or gemcitabine and carboplatin, plus either pembrolizumab or placebo for up to 35 doses, until intolerable toxicity or progressive disease.
The primary analysis revealed an overall survival hazard ratio of 0.73 among patients with a CPS of at least 10, 0.68 for those with a CPS score of at least 1, and 0.89 in the intent-to-treat population. For progression-free survival, hazard ratios were 0.66, 0.75, and 0.82, respectively. At data cutoff, 636 individuals were evaluable.
In the subgroup analysis, the overall survival among CPS subgroups of 1 to 9, 10 to 19, and 20 or greater was 13.9, 20.3, and 24.0 months with pembrolizumab and 15.5, 17.6, and 15.6 with placebo, respectively; hazard ratios were 1.09, 0.71, and 0.72. The progression-free survival among CPS subgroups of 1 to 9, 10 to 19, and 20 or greater was improved among patients given pembrolizumab versus placebo (5.7, 9.9, and 9.2 months vs. 5.6, 7.6, and 5.4 months); hazard ratios were 0.85, 0.70, and 0.62.
Disclosure: For full disclosures of the study authors, visit sabcs.org.
