Abstract
BACKGROUND: Obesity is associated with an increased risk for recurrence and all-cause mortality in breast cancer survivors. Excess adiposity is associated with increased estrogen, insulin, and leptin, and with decreased sex hormone binding globulin (SHBG) concentrations, which may promote breast cancer progression and recurrence. This study aimed to assess the effects of weight loss on these factors. PATIENTS AND METHODS: Breast cancer survivors who were overweight or obese (n = 220) and who were enrolled in a weight loss intervention study provided baseline and follow-up blood samples and weight data. Serum estrogens, SHBG, insulin, and leptin were measured at baseline, 6 months, and 18 months. RESULTS: Weight loss of ≥5% of initial weight decreased leptin and insulin compared with those who did not achieve that amount of weight loss (P < .0001). Weight loss also increased SHBG at 6 and 18 months (P < .01). Postmenopausal women who lost ≥5% of body weight at 6 months had lower estrone (P = .02), estradiol (P = .002), and bioavailable estradiol (P = .001) concentrations than women who did not lose at least 5% of body weight, and weight loss at 18 months was significantly related to a change in serum bioavailable estradiol concentration (P = .02). CONCLUSIONS: Favorable changes in estrogens, SHBG, insulin, and leptin were observed in association with weight loss in these women who were overweight or obese and who had been diagnosed and treated for breast cancer. Weight loss appears to have favorable effects on hormonal and biologic factors associated with increased risk for recurrence and poorer prognosis.