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Improvements in Breast Cancer Characteristics Associated With Bariatric Surgery
*Keyvan Heshmati, *Elisha Pranckevicius, *Ali Ardestani, *David A Harris, Ali Tavakkoli, Eric Sheu
Brigham and women's hospital, Boston, MA

Objective: Bariatric surgery is associated with reduced cancer risk. We assessed the impact of bariatric surgery on breast cancer biology, treatment, and outcomes.
Design: Retrospective, case-control study
Setting: Academic tertiary center
Patients: 44 patients diagnosed with breast cancer (1999-2015) after bariatric surgery were matched based on age, pre-bariatric surgery body mass index (BMI), menopausal status, and date of cancer diagnosis to 88 obese patients with breast cancer who have no bariatric surgery.
Main Outcome Measures: BMI, cancer stage and pathology at diagnosis, surgery, medical therapy, recurrence, and disease-specific mortality were collected from medical records. Analysis was performed in R, using conditional logistic regression, studentís t-test, and Chi2 test.
Results: Breast cancers, diagnosed post-bariatric surgery, presented at an earlier stage, compared to control (Table 1). Further, human epidermal growth factor receptor-2 positive (HER2+) tumors were markedly reduced in the surgery group. No differences were seen in estrogen or progesterone receptor expression. Surgical approaches and outcomes were unchanged, but in the bariatric surgery group, chemotherapy and radiation were used less frequently (Table 2). There were trends toward reduced cancer specific recurrence and mortality post-bariatric surgery (Table 2).
Conclusions: In the obese patient with breast cancer, previous bariatric surgery is associated with the development of lower stage, HER2 negative tumors, which require less chemo- and radio-therapy. These findings suggest bariatric surgery may influence breast cancer biology and outcomes.

Table 1. Patient and Breast Cancer Characteristics
Bariatric surgery
BMI Pre-bariatric surgery (kg/m2)45.72NA0.23**
BMI at Breast cancer diagnosis (kg/m2)34.6144.26
Menopause (%)63631
Stage (%)011150.03
LN+ (%)25500.29
Tumor size(cm)1.502.140.03
ER + (%)89892.32(0.75-7.18)0.14
PR + (%)82731.96(0.70-5.45)0.19
HER2 + (%)14440.12(0.03-0.44)0.001
Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index; ER +, estrogen receptor positive; PR+, progesterone receptor positive; LN+, lymph node positive breast cancer.
* Odds ratio represents outcomes of conditional logistic regression. Studentís t-test and Chi2 analysis was used where appropriate.
**Comparison between BMI pre-bariatric surgery in bariatric surgery group and BMI at breast cancer diagnosis in controls.

Table 2. Cancer Treatment and Outcomes
Bariatric surgery
( n=44)
Breast conserving therapy (%)59531.44(0.65-3.20)0.36
Re-excision (%)3446.50.71(0.30-1.64)0.42
Chemotherapy (%)29.552033(0.13-0.83)0.01
Radiotherapy (%)59840.21(0.006-0.66)0.008
Recurrence (%)7170.30(0.06-1.45)0.13
Cancer specific mortality (%)290.26(0.03-2.21)0.22
Abbreviations: OR, odds ratio; CI, confidence interval
*Odds ratio represents outcomes of conditional logistic regression

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