Meta-analysis links BMI to breast cancer subtype risk with menopausal status differences

This systematic review and meta-analysis examined body mass index (BMI) categories and breast cancer subtype risk across 2,103,181 pre- and post-menopausal women, using data from PubMed, Embase, and Cochrane databases. The analysis compared overweight (BMI 25-29.9 kg/m²) and obese (BMI ≥30 kg/m²) women to under/normal weight women (BMI<25 kg/m²), assessing risk for ER-positive, ER-negative, HER2-positive, and triple-negative breast cancer subtypes.

For postmenopausal women, obesity was associated with moderate higher risk of ER-positive breast cancer (pOR 1.29, 95% CI 1.18-1.41), while overweight status showed increased risk for both ER-positive (pOR 1.14, 95% CI 1.06-1.22) and HER2-positive (pOR 1.13, 95% CI 1.05-1.22) subtypes. In premenopausal women, overweight status was associated with reduced risk of ER-positive breast cancer (pOR 0.80, 95% CI 0.71-0.91) but increased risk of ER-negative (pOR 1.15, 95% CI 1.05-1.26) and triple-negative breast cancer (pOR 1.30, 95% CI 1.15-1.47).

Safety and tolerability data were not reported in this meta-analysis. The authors note that the relationship between BMI and breast cancer subtypes in pre- and post-menopausal women remains incompletely characterized, representing a key limitation. Follow-up duration and absolute event numbers were not provided.

These findings from observational data suggest BMI's association with breast cancer risk differs substantially by menopausal status and molecular subtype. While obesity appears consistently linked to increased postmenopausal ER-positive breast cancer risk, the pattern in premenopausal women is more complex, with overweight status potentially protective for ER-positive disease but risk-enhancing for more aggressive subtypes. Clinical interpretation should consider these associations as observational patterns rather than causal relationships.