Abstract B70: Design of the SHAPE-2 trial; Effects of equivalent weight loss, with and without exercise, on postmenopausal breast cancer risk

Background: Physical inactivity and overweight are two modifiable risk factors for breast cancer. These factors probably act through sex hormone-related pathways. The results of dietary intervention studies (mostly uncontrolled) suggest that diet-induced weight loss reduces postmenopausal sex hormone levels. The question remains if the beneficial effect of physical activity on breast cancer risk is fully explained by the accompanied weight loss. Three out of four exercise intervention studies showed that physical activity mainly influences hormone levels when concordant loss of body fat is achieved. One intervention study, however, suggests an effect of exercise on sex hormones independent of changes in adiposity. Therefore, we set out to study the effect of weight loss mainly driven by exercise compared to equivalent diet induced weight loss only on sex hormone levels. Methods/Design: We designed a three-armed, single blind, two-centre trial in 250 sedentary, postmenopausal women who are overweight/obese (BMI 25-35 kg/m2). Women are randomly allocated to a (1) Diet induced weight loss group, (2) Exercise induced weight loss group or (3) a stable weight Control group. The aim of both intervention groups is to loose an equivalent amount of 5-6 kg body weight in 10 to 14-week timeframe. The Diet-group will therefore follow an energy restricted diet. The Exercise-group will participate in a 16-week endurance and strength training programme (4 hours/week) combined with a slight caloric intake restriction. Measurements include blood sampling, questionnaires, anthropometrics, maximal exercise test, total body DEXA-scan (body (fat) composition) and MRI (abdominal fat). The main outcomes are endogenous serum levels of estradiol, estrone, testosterone and sex hormone binding globulin (SHBG). Discussion: This study will give insight in the possible attributable effect, and the underlying mechanisms, of physical activity on endogenous sex hormone levels, directly and/or mediated by changes in body(fat) composition, in postmenopausal women. Eventually this may lead to the design of more specific guidelines on lifestyle interventions and physical activity for prevention of breast cancer. Citation Format: Willemijn AM van Gemert, Petra HM Peeters, Jantine A. Schuit, Evelyn M. Monninkhof. Design of the SHAPE-2 trial: Effects of equivalent weight loss, with and without exercise, on postmenopausal breast cancer risk. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B70.