Mammographic breast density decreases after bariatric surgery.

Purpose: Breast density (BD), an important risk factor for breast cancer, can change over time in some women, but the underlying mechanism is unclear. Very little is known about the impact of surgical weight loss on BD. Our hypothesis is that weight loss after bariatric surgery is associated with a significant and favorable change in mammographic BD.
Methods: We identified 1097 women 40 years of age or older who underwent gastric bypass or sleeve gastrectomy at our institution from 2010 to 2014. Women who did not have either pre- and post-bariatric surgery mammograms performed at our institution were excluded; 110 had both mammograms and comprised the cohort. Breast density was determined both qualitatively, using reported BI-RADS density, and quantitatively, using the Laboratory for Individualized Breast Radiodensity Assessment.
Results: Qualitative BI-RADS density, quantitative breast area, and percent BD significantly decreased in post-bariatric surgery mammograms (p = 0.009, <0.001, and <0.001, respectively).
Conclusions: Our retrospective study demonstrated that surgical weight loss was associated with a significant decrease in breast density. Additional studies are warranted to validate our findings and elucidate the molecular mechanisms underlying breast density change after weight loss surgery.