Body Roundness Index and Cancer Risk in Postmenopausal Women: Findings from the Women's Health Initiative.

Background Body Roundness Index (BRI) is an anthropometric measure that combines waist circumference and height. It reflects central adiposity more accurately than body mass index (BMI). Evidence linking BRI to long-term cancer risk, particularly in postmenopausal women, remains limited. Methods We examined associations between BRI and incident site-specific cancers (n=33,892) in 144,865 postmenopausal women aged 50-79 years at enrollment into the Women's Health Initiative and followed for a median of 17.9 years. BRI was assessed at baseline in all participants and at year 3 in 60% of participants. Cox proportional hazards models estimated associations between BRI and cancer incidence, adjusting for sociodemographic, reproductive, and lifestyle factors. Results Higher BRI levels were associated with increased risks of kidney, endometrial, liver, esophageal, thyroid, colorectal, stomach, pancreas, bladder, breast, and lung cancers, and with non-Hodgkin's lymphoma, particularly diffuse large B-cell lymphoma. Adjustment for BMI attenuated associations for endometrial, breast, and kidney cancers but strengthened those for liver, lung, and esophageal cancers. Results were consistent across sensitivity analyses and models incorporating repeated BRI measurements. Age-stratified (< /≥ 63 years) models indicated stronger associations for kidney cancer among younger women and a significant positive association for melanoma among older women. Conclusions Among postmenopausal women, higher BRI was associated with increased risk of cancer at multiple sites independently of BMI. These findings support an important role for central adiposity in cancer risk beyond overall body size. Impact In postmenopausal women, BRI may improve estimation of site-specific cancer risk beyond BMI by capturing central adiposity.