Incidence, characteristics, and clinical impact of serious adverse events in patients with breast cancer receiving antineoplastic treatment in the ambulatory setting.

Patients with breast cancer experience various types of adverse events (AEs) during their treatment journey. We aimed to evaluate the incidence, characteristics, and impact of serious AEs in breast cancer patients receiving antineoplastic treatment in the ambulatory setting. A 4-month prospective observational study that included patients with breast cancer treated in the chemotherapy infusion clinics. Patients were assessed for serious AEs, defined as any AE that resulted in a visit to the emergency department (ED) with or without hospital admission, or required any clinical intervention, which were considered as the addition of supportive medications or modifications to the treatment protocol. Characteristics of the patients and antineoplastic regimens as well as the type of AEs were recorded. During the study period, 1168 patients received 2547 cycles. The mean age was 50 ± 11.6 (SD) years and patients had received a median (IQR) of 3 (1-5) treatment cycles prior to enrollment. Among the study cohort, 465 patients(40%) developed at least one serious AE. A total of 660 (26%) cycles were associated with 757 AEs, which required ED visits, addition of supportive medications, and modifications to the treatment protocol in 58%, 29%, and 17% of the cycles, respectively. Most common AEs were musculoskeletal (n = 132, 17%) and gastrointestinal (n = 125, 16.5%). Taxane-based regimens were associated with the most AEs (n = 286, 38%). In a cohort of patients with breast cancer treated in the ambulatory setting, 4 out of 10 patients developed at least one serious AE during the study period. Future research should identify measures to reduce the incidence and severity of such complications.