BACKGROUND

Obesity, classified by body mass index (BMI), is associated with higher postmenopausal breast cancer (BCa) risk. Yet, the associations between abdominal visceral (VAT) and subcutaneous adipose tissue (SAT) with BCa are unclear.

METHODS

We assessed BCa associations with abdominal VAT and SAT in a prospective cohort of postmenopausal women without a history of cancer and with 27 years follow-up (N = 9950), during which all new cancers were adjudicated. Dual-energy x-ray absorptiometry scans assessed adiposity at baseline, year 3, and year 6. Competing-risks multivariable sub-hazard ratios (SHR), with adjustments for sociodemographic, behavioral, reproductive, and anthropometric characteristics, were estimated for baseline and time-dependent associations between VAT, SAT, and incident BCa.

RESULTS

Participants averaged 63.3 ± 7.4 years of age and a BMI of 28.20 ± 5.72 kg/m2 at baseline. The models included 738 incident BCa case patients (N = 593 invasive; N = 145 in situ). Baseline VAT and SAT area were associated with statistically significantly increased BCa risk, by 36% and 19%, respectively. Increasing VAT/SAT ratio was associated with an 8% increase in incident BCa. Time-dependent models produced similar results. VAT and VAT/SAT associated BCa risk was highest for African American/Black women, although not statistically significantly different from other groups. Quartiles (Q) of VAT/SAT were also explored; the SHR for Q4 compared with Q1 was 1.49 (95% CI = 1.18 to 1.87).

CONCLUSION

Higher abdominal VAT and SAT are associated with an increased risk of postmenopausal BCa, and VAT/SAT may provide a distinctive risk estimate. Potential racial and ethnic differences require replication in a larger sample (Women's Health Initiative; NCT00000611; https://clinicaltrials.gov/study/NCT00000611).