Patterns of Anthracycline-Based Chemotherapy-Induced Adverse Drug Reactions and Their Impact on Relative Dose Intensity among Women with Breast Cancer in Ethiopia: A Prospective Observational Study

BACKGROUND: The breast cancer chemotherapy leads to diverse aspects of noxious or unintended adverse drug reactions (ADRs) that cause the relative dose intensity (RDI) reduced to below optimal (i.e., if the percentage of actual dose received per unit time divided by planned dose per unit time is less than 85%). Hence, this prospective observational study was conducted to evaluate chemotherapy-induced ADRs and their impact on relative dose intensity among women with breast cancer in Ethiopia. METHODS: The study was conducted with a cohort of 146 patients from January 1 to September 30, 2017, Gregorian Calendar (GC) at the only nationwide oncology center, Tikur Anbessa Specialized Hospital (TASH), Addis Ababa, Ethiopia. The ADRs of the chemotherapy were collected using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) (version 4.03). The patients were personally interviewed for subjective toxicities, and laboratory results and supportive measures were recorded at each cycle. SPSS version 22 was used for analysis. RESULTS: Grade 3 neutropenia (23 (15.8%)) was the most frequently reported ADR among grade 3 hematological toxicity on cycle 4. However, overall grade fatigue (136 (93.2%)) and grade 3 nausea (31 (21.2%)) were the most frequently reported nonhematological toxicities on cycle 1. The majority of ADRs were reported during the first four cycles except for peripheral neuropathy. Oral antibiotics and G-CSF use (17 (11.6%)) and treatment delay (31 (21.2%)) were frequently reported on cycle 3. Overall, 61 (41.8%) and 42 (28.8%) of study participants experienced dose delay and used G-CSF, respectively, at least once during their enrollment. Of the 933 interventions observed, 95 (10%) cycles were delayed due to toxicities in which neutropenia attributed to the delay of 89 cycles. Forty-four (30.1%) of the patients received overall RDI < 85%. Pretreatment hematological counts were significant predictors (P < 0.05) for the incidence of first cycle hematological toxicities such as neutropenia, anemia, and leukopenia and nonhematological toxicities like vomiting. CONCLUSION: Ethiopian women with breast cancer on anthracycline-based AC and AC-T chemotherapy predominantly experienced grade 1 to 3 hematological and nonhematological ADRs, particularly during the first four cycles. Neutropenia was the only toxicity that led to RDI < 85%. Thus, enhancing the utilization of G-CSF and other supportive measures will improve RDI to above 85%.