Real-World Analysis of Immunotherapy Related Toxicities in Patients with Triple Negative Breast Cancer Receiving Therapy per Keynote-522

Early-stage triple-negative breast cancer (TNBC) carries a high risk of early recurrence and is associated with elevated mortality and morbidity. The KEYNOTE-522 trial, a randomized phase I study, investigated the efficacy of pembrolizumab, an immunotherapy agent, combined with chemotherapy in treating TNBC (Schmid et al., 2022). The trial demonstrated a pathological complete response rate of 64.8% in the chemotherapy-immunotherapy group compared to 51.2% in the chemotherapy-placebo group. Following these findings, pembrolizumab with neoadjuvant chemotherapy received Health Canada approval and has since become the standard of care for TNBC. While the KEYNOTE-522 trial provided pivotal insights, real-world data on the adverse events and toxicities of this regimen remain limited but are perceived significant (Marhold et al., n.d.). Emerging evidence suggests that toxicity rates in clinical practice may exceed those reported in the trial (SABCS 2022, n.d.). In this study, we retrospectively analyzed data from patients treated according to the KEYNOTE-522 protocol, examining demographic characteristics, treatment outcomes, and rates of immunotherapy-related toxicities to compare with trial data. Our analysis identified higher rates of grade 1, 2, and 3 toxicities in our cohort than those reported in KEYNOTE-522. Furthermore, a significant proportion of patients required discontinuation of immunotherapy due to adverse events. These findings highlight the challenges of translating clinical trial protocols into real-world practice, as well as the need for robust toxicity monitoring tools to optimize patient outcomes. Future research will focus on implementing an intuitive reporting tool to assist patients and healthcare providers in promptly identifying and managing grade 2 toxicities.