Zoledronic acid ameliorates the effects of endocrine therapy on bone health in women with early-stage breast cancer

In this Practice Point commentary, I discuss the findings and clinical implications of the bone substudy of the phase III, open-label, randomized Austrian Breast and Colorectal Cancer Study Group trial-12 (ABCSG-12). Gnant et al. assessed changes in BMD in 404 premenopausal women with early-stage breast cancer who received different adjuvant endocrine therapies, with or without concomitant bone-protective therapy (4 mg intravenous zoledronic acid twice-yearly). The authors demonstrated rapid bone loss after ovarian suppression with goserelin plus either a selective estrogen-receptor modulator (tamoxifen) or an aromatase inhibitor (anastrozole). Bone loss was particularly marked in patients who received a combination of goserelin and anastrozole; losses were only partially reversed on treatment withdrawal. Zoledronic acid prevented bone loss associated with both endocrine therapies. The study of Gnant et al. provides useful descriptive data, but is limited by its lack of data on fracture incidence. Furthermore, the authors were unable to define the specific population of patients who require intervention with a bisphosphonate.