The use of adjuvant bisphophonates in the treatment of early-stage breast cancer.

Adjuvant treatment of breast cancer has resulted in significant improvement in breast cancer-related outcomes. In addition to chemotherapy and endocrine therapy, the bone-protective agents known as bisphosphonates have been extensively investigated for their putative antitumor effect. Backed by strong preclinical data from in vitro and in vivo models, several randomized clinical trials have evaluated the role of bisphosphonates in an adjuvant setting. The recent NSABP B-34 (National Surgical Adjuvant Breast and Bowel Project protocol B-34) and AZURE (Adjuvant Zoledronic Acid to Reduce Recurrence) studies found no disease-free survival benefit with clodronate and zoledronate, respectively, whereas the ABCSG-12 (Austrian Breast and Colorectal Cancer Study Group trial 12) study found improvement in disease-free survival with zoledronate. Data from these trials suggested a beneficial effect of bisphosphonates in older, postmenopausal women and in premenopausal women treated with ovarian suppression. Given the acceptable toxicity profile of bisphosphonates, these agents could be a useful adjunct to adjuvant chemotherapy or endocrine treatment for early-stage breast cancer in a carefully selected subset of patients. This review aims to critically synthesize the results of clinical trials of adjuvant bisphosphonates in early-stage breast cancer, and to provide guidelines for the use of these agents in early-stage breast cancer.