Background: Women who exercise after breast cancer diagnosis have a lower risk of recurrence and mortality, but the biological mechanisms through which exercise impacts breast cancer are unclear. The Pre-Operative Health and Body (PreHAB) Study was a randomized window of opportunity trial designed to test the impact of exercise on tissue and serum biomarkers in women with early breast cancer. Methods: Inactive women with newly diagnosed Stage I-III breast cancer were enrolled through Dana-Farber Cancer Institute and Yale University prior to surgery. Participants were randomized 1:1 to an exercise intervention or Mind-Body control intervention and participated in the interventions between enrollment and the time of surgery. Tumor tissue and serum were collected at enrollment and surgery. Results: A total of 49 women were randomized (27 exercise and 22 control). At baseline, mean age was 52.6, BMI was 30.2kg/m2 and exercise was 49 min/wk. Mean time between enrollment and surgery was 4.2 weeks. Exercise participants significantly increased minutes of weekly exercise vs. controls (203 vs. 23, p<0.0001). Tumor expression of insulin receptor (IR) decreased significantly in the exercise group vs. controls (Table). There was no difference in change in Ki-67. Exercise participants experienced a significant decrease in serum leptin and a trend toward a decrease in IGF-1 compared to controls. Conclusions: A brief pre-operative exercise intervention led to alterations in metabolic but not proliferative markers in serum and breast tumor tissue. This study provides some of the first data regarding the impact of exercise on human breast cancer, offering insight into the biologic basis of the protective effect of exercise on breast cancer. Clinical trial information: NCT01516190

All changes reported as mean (SD)