Dense Breasts, High BMI May Interact to Up Breast Cancer Risk

Positive additive interaction linked to increased risk for breast cancer particularly in postmenopausal women

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WEDNESDAY, Jan. 12, 2022 (HealthDay News) -- Breast density and body mass index (BMI) may interact synergistically to heighten breast cancer risk, with a stronger association found among postmenopausal women, according to a study published online Dec. 23 in JAMA Network Open.

Thi Xuan Mai Tran, Ph.D., from Hanyang University in Seoul, South Korea, and colleagues examined the interaction between mammographic breast density and BMI and its association with breast cancer risks among premenopausal and postmenopausal women. The analysis included about 3.2 million premenopausal, cancer-free women and roughly 4.4 million postmenopausal, cancer-free women (aged 40 years and older) who underwent mammographic screening between 2009 and 2013, with follow-up data through 2018.

The researchers found that increased breast density was associated with an increased risk for breast cancer in both premenopausal and postmenopausal women across BMI categories. Premenopausal women with Breast Imaging Reporting and Data System (BI-RADS) category 4 density had a twofold higher risk for breast cancer regardless of BMI (all women: adjusted relative risk [aRR], 2.36; underweight: aRR, 1.80; normal weight: aRR, 2.10; overweight: aRR, 2.47; obese: aRR, 2.87) versus women with underweight status and BI-RADS category 1 density. An association between BMI and risk for breast cancer was seen only in postmenopausal women, regardless of breast density category (BI-RADS category 4, all women: aRR, 2.91; underweight: aRR, 2.74; normal weight: aRR, 3.05; overweight: aRR, 2.85; obese: aRR, 2.52) versus underweight women with BI-RADS category 1. For high breast density and high BMI, there was a significant positive, additive interaction (premenopausal women: adjusted relative excess risk due to interaction, 0.53; postmenopausal women: adjusted relative excess risk due to interaction, 1.68).

"Women with overweight or obesity and dense breast tissue might benefit from tailored early screening strategies to detect breast cancer," the authors write.

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