New Insights on Pembrolizumab in Early TNBC: Lessons from Real-World Data

Neoadjuvant pembrolizumab given with standard chemotherapy in a single-center Montpellier cohort produced a pathological complete response (pCR) rate of 61.1% in routine practice.

Ninety-two patients with early-stage triple-negative breast cancer (TNBC) were included in a retrospective registry analysis. The treatment combined pembrolizumab with standard neoadjuvant chemotherapy, and pCR was defined as absence of residual invasive disease in the breast and axilla. The cohort reflects unselected, real-world practice (median age 50) and documents common treatment interruptions and discontinuations, offering pragmatic insight into everyday outcomes.

The pathological complete response rate of 61.1% aligns with expectations from controlled trials. In this series, no statistically significant association was found between pCR and the number of pembrolizumab cycles received during the neoadjuvant phase in the Montpellier cohort; extended dosing did not materially change the likelihood of achieving pCR.

Grade 3–4 immune-related adverse events (irAEs) occurred in 20% of patients. The most common severe events were hepatitis, colitis, and dermatologic toxicity; myocarditis, endocrine, and hematologic events were less frequent. Patients who experienced grade 3–4 irAEs had a higher observed pCR rate (80% vs 56.8%), but this difference did not reach statistical significance (p = 0.079).

These data underscore the need to weigh the potential for increased efficacy against the tangible risk of higher-grade toxicity when considering neoadjuvant immunochemotherapy.

Key Takeaways:

• Real-world pCR of 61.1% supports the expected efficacy of adding pembrolizumab to neoadjuvant chemotherapy for early TNBC in routine practice.
• One in five patients experienced grade 3–4 irAEs—most commonly hepatitis, colitis, and skin toxicity—so heightened vigilance for these events is required.
• The trend toward higher pCR among patients with severe irAEs (80% vs 56.8%) is hypothesis-generating and warrants prospective evaluation.