Life-course epidemiology of body size and risk of early and advanced breast cancer.

Abstract

e22627 Background: There has been limited studies of the life-course epidemiology of body sizes and the risk of early and advanced breast cancer (BC) in women, particularly from low- and middle-income countries (LMIC). To overcome the challenge of nonavailability of data, we used somatotypic classification of overall body shape to evaluate critical/sensitive period, cumulative exposure, trajectory and change, and saturated models of association between body sizes at different life stages and BC risk. Methods: We analyzed 960 BC cases from the African Female Breast Cancer Epidemiology (AFBRECANE) study. We categorized self-reported somatotypes as ‘Not large’ or ‘Large’ at multiple life stages and derived trends. The outcomes were early (≤5 cm without chest wall or skin involvement) and advanced ( > 5 cm or any tumor with direct extension to chest wall or skin) stages of breast cancer. We performed multivariable logistic regression, adjusting for factors that were found to be significant during age-adjusted analysis. Results: In adjusted analyses, higher BMI was associated with lower odds of advanced BC stage (OR = 0.94, 95% CI [0.89-0.98], = < 0.01), while older age at menarche was associated with higher odds of advanced BC stage at diagnosis (OR = 1.35, 95% CI [1.14-1.61], p < 0.01). Large body size one year prior to diagnosis was also associated with increased odds of advanced BC stage (OR = 2.88, 95% CI [1.21-6.88], p = 0.02). Body size during early age and at ages 7-10, and somatotype trends across life stages were not independently associated with BC stage in the final adjusted model. Conclusions: Our findings suggest that recent adult body size, BMI, and age at menarche are independently associated with BC tumor stage at diagnosis. While large body size one year prior to diagnosis was associated with increased odds of advanced stage tumor, higher BMI was associated with lower odds. These findings highlight how body size throughout adulthood can influence tumor biology, supporting risk stratification and prevention. Further large, diverse longitudinal studies are warranted.