Obesity increases the risk and tumor aggressiveness in postmenopausal South Indian women diagnosed with breast cancer

BACKGROUND: While global studies have examined the relationship between obesity and breast cancer, region-specific data from South India remain limited. Considering the unique genetic, metabolic, and lifestyle characteristics, this study investigates the association between obesity classified using Asian Indian body mass index (BMI) cutoffs and clinicopathological features, molecular subtypes, and hormone profiles in women with breast cancer. METHODOLOGY: A retrospective observational study was conducted involving 346 women diagnosed with breast cancer at a tertiary care center in South India. Participants were categorized by BMI and assessed for tumor characteristics, molecular subtype, and hormone receptor status. Statistical analysis was performed using Pearson’s Chi-squared test and one-way ANOVA, with significance set at P < 0.05. RESULTS: Among the cohort, 63.9% had obesity, and 67.1% were postmenopausal. Left-sided breast cancer was observed in 52.9% of women. Intermediate and poorly differentiated tumors were more common among women with obesity. Invasive ductal carcinoma was the predominant histologic type, with a higher frequency in obese women (57.75%). Luminal A was the most frequent molecular subtype, followed by the triple-negative subtype, in women with obesity. Of the 120 patients positive for Ki-67 expression, 81 (64.28%) were obese. A significant association was observed between Ki-67 and molecular subtype ( P = 0.042). Postmenopausal women with obesity had a 5.63-fold higher odds of developing breast cancer. CONCLUSION: This study demonstrates a strong association between obesity and aggressive tumor features in South Indian women. Findings underscore the prognostic value of Ki-67 and the importance of tailored lifestyle interventions in obese postmenopausal women to reduce breast cancer burden.