6/28/23, 11:52 PM KEYNOTE-355 Pathway Feedback Search Clinical Topics Home Studies KEYNOTE 355 KEYNOTE 355 Trial question What is the role of pembrolizumab chemotherapy in patients with metastatic triple-negative breast cancer? Study design Multi-center Double blinded RCT Population 847 female patients Inclusion criteria: patients with untreated locally recurrent inoperable or metastatic triple- negative breast cancer Key exclusion criteria: treatment with an investigational agent within 4 weeks; failure to recover from adverse events owing to previously administered therapy; immunodeficiency or immunosuppressive therapy within the previous week; Interventions N=566 pembrolizumab chemotherapy (pembrolizumab 200 mg every 3 weeks plus nab- paclitaxel, paclitaxel, or gemcitabine/carboplatin) N=281 placebo chemotherapy (matching placebo plus nab-paclitaxel, paclitaxel, or gemcitabine/carboplatin) Primary outcome Progression-free survival in patients with Combined Positive Score 10 9.7 months 9.7 7.3 months 5.6 4.8 months 2.4 months Significant increase 0.0 months Pembrolizumab chemotherapy Placebo chemotherapy Significant increase in progression-free survival in patients with CPS 10 (9.7 months vs. 5.6 months; HR 1.35, 95% CI 1.12 to 1.64) Secondary outcomes https://web.pathway.md/studies/recorb7hkSAGQnMEO 1/2 6/28/23, 11:52 PM KEYNOTE-355 Pathway Significant increase in progression-free survival in patients with CPS 1 (7.6 months vs. 5.6 months; HR 1.54, 95% CI 1.16 to 2.04) No significant difference in progression-free survival in patients with CPS < 1 (6.3 months vs. 6.2 months; HR 1.08, 95% CI 0.77 to 1.53) Borderline significant increase in progression-free survival in intention to treat population (7.5 months vs. 5.6 months; HR 1.33, 95% CI 1.08 to 1.64) Safety outcomes No significant difference in any adverse event. Conclusion In patients with untreated locally recurrent inoperable or metastatic triple-negative breast cancer, pembrolizumab chemotherapy was superior to placebo chemotherapy with respect to a progression-free survival in patients with CPS 10. Reference Javier Cortes, David W Cescon, Hope S Rugo et al. Pembrolizumab plus chemotherapy versus placebo plus chemotherapy for previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer (KEYNOTE-355): a randomised, placebo-controlled, double-blind, phase 3 clinical trial. Lancet. 2020 Dec 5;396(10265):1817-1828. Open reference URL https://web.pathway.md/studies/recorb7hkSAGQnMEO 2/2