Pembrolizumab Plus Chemotherapy Show Efficacy for TNBC in KEYNOTE-355

Javier Cortes, MD, PhD, head of Breast Cancer and Gynecological tumors in the Oncology Department at the Ramón y Cajal University Hospital, discusses the data from the phase 3 KEYNOTE-355 trial of pembrolizumab (Keytruda) and chemotherapy versus placebo and chemotherapy for previously untreated patients with locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC).

Data from this study were presented at the 2020 American Society of Clinical Oncology Virtual Scientific Program. One of the coprimary end points of progression-free survival (PFS) in patients with PD-L1 with a Combined Positive Score (CPS) of 10 or more was met and had a hazard ratio of 0.65. Cortes says this is statistically significant and has great clinical importance. The median PFS was 5.6 months in the placebo arm compared with 9.7 months in the pembrolizumab arm.

Now that this primary end point had been achieved, the investigators are looking at the PFS data in patients with CPS of 1 or more. The PFS trend for these patients was clear, with a hazard ratio of 0.74, but the P value did not reach statistical significance at 0.0014, according to Cortes. The PFS data in the intention-to-treat population was not formally tested in KEYNOTE-355. Regarding the activity of pembrolizumab and chemotherapy, this regimen improved PFS for patients with PD-L1 expression and a CPS of 10 or more, he concluded.

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