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.