Updated long-term overall survival (OS) data from the phase 3 KEYNOTE-522 trial demonstrate a significant benefit for pembrolizumab (Keytruda) plus chemotherapy in patients with high-risk, early-stage triple-negative breast cancer (TNBC). The study, presented at the 2024 ESMO Congress, reinforces the role of pembrolizumab in improving outcomes for this patient population.
The KEYNOTE-522 trial evaluated pembrolizumab in combination with neoadjuvant chemotherapy followed by surgery and adjuvant pembrolizumab or placebo. Previous results indicated that adding pembrolizumab to chemotherapy significantly increased pathologic complete response (pCR) rates by approximately 30.6%, with a pCR rate of 64.8% (95% CI, 59.9%-69.5%) vs 51.2% (95% CI, 44.1%-58.3%) in the placebo arm (estimated treatment difference, 13.6%; 95% CI, 5.4%-21.8%; P < .001).
Sustained Survival Advantage
At a median follow-up of 75.1 months (range, 65.9-84.0), the 60-month event-free survival (EFS) rate was statistically significant in favor of the pembrolizumab plus chemotherapy arm, at 81.2% compared with 72.2% in the placebo plus chemotherapy arm (HR, 0.65; 95% CI, 0.51-0.83). The proportion of patients experiencing an EFS event, such as recurrence, progression, or death, was lower in the pembrolizumab group, at 20.3% compared with 29.2% in the placebo group.
Overall Survival Improvement
The 5-year OS rates were 86.6% (95% CI, 84.0%-88.8%) in the pembrolizumab arm vs 81.7% (95% CI, 77.5%-85.2%) in the placebo arm (HR, 0.66; 95% CI, 0.50-0.87; P = .00150). In total, 14.7% of patients in the pembrolizumab arm had an OS event vs 21.8% of those in the placebo arm.
Expert Commentary
"What we haven’t [had] until now were the long-awaited overall survival data. This is only a key secondary end point, but it’s of course, from a patient perspective, the most important end point,” said Dr. Peter Schmid, MD, PhD, FRCP, professor, cancer medicine, Barts Cancer Institute, Queen Mary University of London. He concludes that these long-term data further solidify the role of pembrolizumab as part of the standard treatment strategy for this patient population.
