Study design & participants
The prospective study was initiated at the University of Zimbabwe, Faculty of Medicine and Health Sciences at Parirenyatwa Hospital (PH) in Harare. The study recruited 50 Zimbabwean patients above the age of 18 years receiving doxorubicin chemotherapy for breast cancer over a period of 6 months from January 2019-July 2020. The patients were sampled using purposive sampling to reflect the demographics of black breast cancer patients from Zimbabwe. Participants underwent cardiovascular assessment by a cardiologist using echocardiography to measure Left Ventricular Ejection Fraction (LVEF) at baseline, 3 months, 6 months and 12 months. Patients with prior treatment with any chemotherapy, prior chest wall radiotherapy and non-black women were excluded. Demographics, body mass index (BMI) and physical performance of the patients was recorded at the time of recruitment. A blood specimen was collected at the study entry from which the genotype for the three cardiotoxicity risk variants was determined. The genotypes were checked for any deviation from the Hardy Weinberg principle (HWE) before their frequencies were determined using χ2. The association analysis of genotypes and LVEF measures was done using multivariable logistic regression. A patient with cardiotoxicity was defined as having LVEF threshold of greater than 10% reduction from the normal echocardiograms (normal ≥60%) 19,20.