Should bisphosphonates be utilized in the adjuvant setting for breast cancer?

Adjuvant therapies for early breast cancer are associated with substantial decreases in bone mineral density. Bisphosphonates are antiresorptive agents that have an established role in preventing skeletal morbidity in patients with bone metastases and in the treatment of osteoporosis. Recently, several trials have demonstrated the efficacy of bone-directed agents for prevention of cancer treatment-induced bone loss in both premenopausal and postmenopausal women with early stage breast cancer. Moreover, it is now becoming evident that bisphosphonates may also exert anticancer effects in the adjuvant setting. For example, long-term follow-up of a study in patients with bone marrow micrometastases from breast cancer revealed overall survival benefits for clodronate versus placebo, and an ongoing large trial may provide further insights. Addition of twice-yearly zoledronic acid to standard adjuvant endocrine therapy significantly improved disease-free survival and decreased disease recurrence compared with standard therapy alone in 3 clinical trials involving nearly 3,500 patients with stage I-IIIA breast cancer, and monthly zoledronic acid during neoadjuvant therapy decreased residual tumor volume and improved pathologic response in patients with stage II/III breast cancer. Overall, a large and growing body of evidence suggests the potential adjuvant benefits of bisphosphonates in early breast cancer.