57 - Bisphosphonates in Early Breast Cancer

Abstract

Bisphosphonates are osteoclast inhibitors used to treat osteoporosis. In oncology, bisphosphonates are used to prevent or treat skeletal-related events such as pathologic fractures and hypercalcemia of malignancy. In early breast cancer, these drugs have been used to prevent or treat bone loss associated with the use of aromatase inhibitors. It is thought that bisphosphonates also exert an anticancer effect by altering the tumor microenvironment in the bone. Individual clinical trials of adjuvant bisphosphonates were inconclusive, although few of these trials generated the hypothesis that such an anticancer effect is limited to postmenopausal women. An individual patient-level data meta-analysis of 26 clinical trials including 18,766 women with early breast cancer, treated with bisphosphonates or control, found borderline significant reductions with the use of bisphosphonates for distant recurrence, bone recurrence, breast cancer mortality, and all-cause mortality. A subgroup analysis noted lack of benefit in premenopausal women. In postmenopausal women, there were significant reductions in bone recurrences and breast cancer mortality. Therefore all postmenopausal women (natural or induced), especially those on antiestrogen therapy, should be considered for adjuvant bisphosphonate treatment, and decision to treat should be individualized.