Attributable breast cancer burden in Malaysia: mammographic density, lifestyle, and hereditary factors

PURPOSE Large prospective studies in high-income countries have enabled the estimation of preventable cancer cases, guiding cancer control strategies. With breast cancer incidence rising rapidly in Malaysia, there is an urgent need for locally relevant data to inform effective prevention and control measures. We quantified the population-level contribution of risk factors in Malaysia using population-specific prevalence and literature-based relative risks. METHODS We calculated population attributable risk (PAR) using: (1) Malaysia-specific prevalence from national surveys and local epidemiological studies, and (2) relative risks derived from meta-analyses of Asian prospective cohorts or large case-control studies. We estimated attributable proportions using Levin’s formula, adjusted for the joint effects of risk factors with a multiplicative model, and generated simulation-based confidence intervals to quantify their impact on overall disease burden. RESULTS Mammographic density (MD) accounted for 32.8% (95% CI: 6.6–68.0) of breast cancer burden in Malaysian women, followed by elevated body mass index (BMI, 14.7%, 0.2–36.4), and passive smoking (10%, 0-18.4). Family history and genetic factors collectively contributed 12.1% (5.3–19.8). Reproductive factors play a pronounced role before menopause, whereas metabolic factor predominate after menopause. Their impact varies across ethnicities and birth cohorts: MD was most influential among Chinese women, elevated BMI among Malays and Indians, and both MD and obesity had greater impact in women born after 1945. CONCLUSION A substantial proportion of the breast cancer burden in Malaysia appears attributable to modifiable risk factors. Our study supports optimizing local prevention and screening strategies to reflect age patterns, ethnic diversity, and contemporary risk.