Genetic and Environmental Risk Factors for Breast Cancer Among Women in Owerri, South East Nigeria: A Case-Control Study

Breast cancer aetiology involves complex interactions between genetic predisposition and environmental exposures. In Nigeria, the specific contributions of BRCA mutation status, reproductive history, and lifestyle factors to breast cancer risk in the local population remain inadequately characterized. This case-control study examines genetic and environmental risk factors for breast cancer among women in Owerri, Imo State, South East Nigeria, from 2021 to 2023. Cases comprised 120 histologically confirmed breast cancer patients, while 240 age-matched cancer-free controls were recruited from the same communities. Variables assessed included family history of breast cancer, parity, age at menarche and menopause, breastfeeding duration, oral contraceptive use, BMI, and alcohol consumption. Logistic regression was applied to determine independent risk factors. Family history of first-degree relative breast cancer (OR 3.6), nulliparity (OR 2.4), breastfeeding duration less than 6 months (OR 2.1), and obesity (OR 2.8) were independent risk factors. Oral contraceptive use was not significantly associated after adjustment. The study provides locally relevant risk factor data and recommends community-based breast cancer risk stratification programs, extended breastfeeding promotion, and obesity prevention initiatives targeting women of reproductive age in South East Nigeria. Keywords: breast cancer risk factors, case-control, Owerri, BRCA, South East Nigeria