Adverse events in patients treated with neoadjuvant chemo/immunotherapy for triple negative breast cancer: results from seven academic medical centers.

Purpose: The standard-of-care neoadjuvant treatment for early-stage or locally advanced triple negative breast cancer (TNBC) is the KEYNOTE-522 regimen that combines pembrolizumab and chemotherapy. Although this approach has superior response and survival rates, high-grade adverse events (AEs) are common. Real-world data from a diverse patient population is needed to better understand practice patterns and the impact of immunotherapy in TNBC patients.

Methods: Medical records from TNBC patients were retrospectively reviewed during neoadjuvant and adjuvant treatment with pembrolizumab and chemotherapy. CTCAE version 5.0 was used to grade AEs. Variables were reported with descriptive statistics, and AE, pCR and hospitalization rates were estimated with 95% confidence intervals.

Results: We identified 415 patients from seven academic medical centers; 60% identified as White and 21% as Black. pCR rate was 52%. 88% of patients experienced an AE, 38% experienced a grade 3+ AE, and 31% stopped pembrolizumab early. Hospitalization rate was 26%. There were no statistically significant differences in AE, pCR or hospitalization rates between White and Black patients. Obese patients had a statistically significant higher hospitalization rate (p = 0.014). There were 18 deaths during treatment, mainly from progressive TNBC.

Conclusion: This is one of the largest real-world, diverse patient cohorts for TNBC patients treated with chemotherapy and pembrolizumab. pCR rate was lower than that reported in the KEYNOTE-522 study and in smaller real-world studies, potentially due to high rates of pembrolizumab and chemotherapy discontinuation. AEs and hospitalizations were common, with obese patients more likely to be hospitalized than patients with a normal BMI.