Single-center retrospective study of real-world immune-related adverse events with pembrolizumab for early-stage triple-negative breast cancer

The addition of pembrolizumab to chemotherapy in high-risk early triple-negative breast cancer (TNBC) improves cancer outcomes, but is also associated with increased risk of immune-related adverse events (irAEs) that can be severe and/or lifelong. A retrospective study at MD Anderson Cancer Center (Houston, TX) investigated patterns of irAEs in patients with TNBC who received pembrolizumab outside clinical trials. Eighty of 233 patients (34%) developed 100 separate irAEs. The most common irAEs were endocrinopathies (52%) and gastrointestinal (23%). There were 26 grade ≥ 3 irAEs, which all resulted in hospitalization; 45 required systemic steroids, 16 required additional immunosuppressive therapy, and 32 patients discontinued pembrolizumab because of irAEs. Two patients who developed colitis eventually died due to complications. Most (67 instances) irAEs were unresolved at the time of last follow-up, but 55% (37/67) had improved to grade 1. The authors conclude that irAEs were observed in 34% of real-world patients receiving pembrolizumab for early TNBC.