Age effect on bone mineral density changes in breast cancer patients receiving anastrozole: results from the ARBI prospective clinical trial

PURPOSE: We investigated whether age at anastrozole (A) initiation influences the effect of treatment on bone mineral density (BMD). We conducted a post hoc analysis of the dataset of Arimidex Bone Mass Index Oral Bisphosphonates prospective trial, studying the effect of risedronate (R) on BMD of postmenopausal, early breast cancer patients receiving A. METHODS: Patients were stratified into those with normal BMD or mild osteopenia (T > −2) receiving A-only and patients with mild or severe osteopenia (T ≤ −2) or osteoporosis (T < −2.5) receiving A and per os R (A + R). Depending on age on treatment initiation, patients were grouped into two age cohorts, above and below 65 years. BMD change in lumbar spine (LS) and hip (HP) was evaluated at 12 months. An analysis of patients with normal BMD at baseline was additionally performed. RESULTS: Among patients receiving A-only, women ≤65 years were more likely to have a decrease in LS-BMD than older (p = 0.034). HP-BMD decrease at 12 months was not related to age (p = 0.182). In patients with mild or severe osteopenia or osteoporosis, treated with A + R, no age effect was observed for LS or HP (p = 0.099 and p = 0.939, respectively). Among patients with normal BMD at baseline, the age effect on LS-BMD change was more profound (p = 0.026). CONCLUSIONS: Our study suggests that younger postmenopausal women with normal BMD or mild osteopenia receiving A-only face an increased risk of bone loss in LS. Among patients with mild or severe osteopenia or osteoporosis treated with A + R, 12 months LS or HP BMD variations were configured regardless of age group.