Pembrolizumab for Early-Stage Triple-Negative Breast Cancer: KEYNOTE-522 Japan Subgroup Analysis.

Area of Science:

• Oncology
• Clinical Trials
• Immunotherapy

Background:

• Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options.
• High-risk early-stage TNBC requires effective neoadjuvant and adjuvant therapies to improve outcomes.
• Pembrolizumab, an immune checkpoint inhibitor, has shown efficacy in advanced TNBC.

Purpose of the Study:

• To evaluate the efficacy and safety of neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab in Japanese patients with high-risk early-stage TNBC.
• To present findings from the Japan subgroup of the phase 3 KEYNOTE-522 study.
• To assess pathologic complete response (pCR) and event-free survival (EFS) in this specific population.

Main Methods:

• Phase 3, randomized, double-blind, placebo-controlled study (KEYNOTE-522 Japan subgroup).
• Participants (N=76) with locally advanced TNBC received neoadjuvant pembrolizumab (200 mg) or placebo plus chemotherapy for 8 cycles, followed by surgery and adjuvant pembrolizumab or placebo for up to 9 cycles.
• Primary endpoints: pCR and EFS.

Main Results:

• Pathologic complete response (pCR) rates were 53% with pembrolizumab vs 48% with placebo (difference, 4.9%; 95% CI, -17.6% to 27.1%).
• Event-free survival (EFS) rates at 60 months were 84% for pembrolizumab and 73% for placebo (HR, 0.54; 95% CI, 0.20-1.50).
• Grade 3/4 treatment-related adverse events occurred in 82% of the pembrolizumab arm and 77% of the placebo arm; no Grade 5 AEs were reported.

Conclusions:

• Neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab demonstrated improved efficacy outcomes in Japanese patients with high-risk early-stage TNBC.
• The safety profile was manageable and consistent with previous findings.
• This regimen supports the use of pembrolizumab in this patient population in Japan.