Patterns and Predictors of Carboplatin-Induced Myelotoxicity in Breast Cancer Patients: A Six-Year Retrospective Analysis

Introduction/Background: Carboplatin is widely used in breast cancer (BC) treatment but is limited by its potential for myelosuppression. Data on its hematologic toxicity profile in regional populations remains limited. The objective of this study is to evaluate the incidence, trends, and predictors of carboplatin-induced myelotoxicity in BC patients. Materials and Methods: A six-year retrospective study was conducted at Sultan Qaboos University Hospital, Muscat, Oman, involving 152 BC patients who received carboplatin-containing chemotherapy. Hematological toxicities, including anemia, neutropenia, and thrombocytopenia, were assessed over chemotherapy cycles 1 to 4 using Common Terminology Criteria for Adverse Events (CTCAE) - Version 4.03. Additional analyses included dose intensity, treatment delays, and multivariate regression to identify predictive factors. Results: Anemia was the most common toxicity, with Grade 3–4 cases rising from 22% in cycle 1 to 41% in cycle 4 (p=0.003). Neutropenia (12%) and thrombocytopenia (8%) were less frequent and showed no cumulative trend. Dose intensity significantly declined by 12% from cycle 1 to 4 (p<0.001), and treatment delays increased from 15% to 21% (p=0.04). Predictors of anemia included older age (OR 1.04), low baseline hemoglobin (OR 0.26), and palliative intent (OR 2.68). Neutropenia was associated with low baseline WBC (OR 0.68), palliative treatment (OR 4.32), and absence of gemcitabine (OR 0.12). Discussion: Our population exhibited high-risk features—such as younger age, prior exposure to chemotherapy, and advanced stages. Despite that, the overall rates of neutropenia and thrombocytopenia were relatively low, likely due to dose adjustments and primary G-CSF prophylaxis. Anemia, however, was common and significantly impacted survival. Predictors of toxicity included baseline blood counts and disease stage, with differences observed between carboplatin combinations. Conclusion: Carboplatin-induced myelotoxicity presents primarily as progressive anemia, contributing to reduced dose intensity and increased delays. These findings highlight the need for individualized monitoring and supportive strategies to optimize treatment outcomes.