Prevention of osteoporosis as a consequence of aromatase inhibitor therapy in postmenopausal women with early breast cancer: Rationale and design of a randomized controlled trial

Background: Aromatase inhibitors (AIs) have improved the prognosis for breast cancer survivors and are now standard of care for postmenopausal women with hormone receptor positive early stage breast cancer. One side-effect, however, is a decrease in bone mineral density (BMD) and increased fracture risk. Since hormone replacement therapy (HRT) is contraindicated in these women, one prevention option is exercise combined with vitamin D and calcium. The effect of this intervention on drug-induced osteoporosis is unknown. Methods: A single-blind randomized controlled trial will be undertaken to test the hypothesis that exercise combined with vitamin D and calcium can prevent the decrease in BMD associated with the use of AIs. Sixty postmenopausal women prescribed an AI for the treatment of breast cancer will be randomized into either an exercise or control group. Participants randomized to the exercise group will undertake a 12-month gym-based exercise program, 3 times per week involving resistance and impact training. Participants in the control group will be advised on the benefits of exercise for preventing osteoporosis, but not prescribed exercise. Both groups will receive vitamin D and calcium supplements. The primary outcome will be total hip bone mineral density measured via dual energy X-ray absorptiometry (DXA). Study outcomes will be compared between groups at baseline, 6 months and 12 months. Summary: This study will investigate the effect of exercise in combination with vitamin D and calcium on prevention of drug-induced osteoporosis in postmenopausal women prescribed AIs for the treatment of breast cancer