Changes in Breast Cancer Characteristics Associated with Bariatric Surgery
Keyvan Heshmati1, David Harris1, Elisha Pranckevicius1, Ali Ardestani1, Jennifer Ligibel2, Mehra Golshan1, Bernard Rosner3, Ali Tavakkoli1, Eric Sheu1
1Brigham and Women's Hospital, Boston, MA, USA; 2Dana-Farber Institute, Boston, MA, USA; 3Harvard T.H. Chan School of Public Health, Boston, MA, USA
Background: Bariatric surgery is associated with a reduced risk of developing cancer, particularly in women. We performed a single-institution, case-control study to assess the impact of bariatric surgery on breast cancer characteristics and outcomes.
Methods: 42 subjects diagnosed with breast cancer after bariatric surgery (1989-2014) were matched to 84 subjects with breast cancer (1984-2012) who did not undergo bariatric surgery based on age, BMI at cancer diagnosis, menopausal status, and date of cancer diagnosis. Medical records were extracted for breast cancer and bariatric endpoints. Statistical analysis was performed in R statistical software.
Results: Women who developed breast cancer after bariatric surgery presented at an earlier stage compared to controls (Table 1). Human epidermal growth receptor-2 positive (HER2+) tumors were markedly reduced in the bariatric surgery group (OR 0.16 (0.03-0.76); P=0.02), with no significant differences seen in estrogen and progesterone receptor expression. In subgroup analysis, no HER2+ tumors were found following Roux-en-Y gastric bypass (OR 0.00(0.00-0.43); P=0.002). Surgical approaches and outcomes were unchanged, but in the bariatric surgery group, trastuzumab, chemotherapy and radiation were used less frequently. At a mean follow-up of 5 years, bariatric surgery was associated with trends toward reduced mortality.
Conclusion: In the obese patients with breast cancer, bariatric surgery is associated with the development of earlier stage, HER2-negative tumors. These findings suggest bariatric surgery may influence breast cancer biology and outcomes. 
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