Aromatase inhibitor-induced bone mineral loss and its prevention by bisphosphonate administration in postmenopausal breast cancer patients

Aim: To investigate aromatase inhibitor-induced bone mineral loss and its prevention by bisphosphonate administration in postmenopausal breast cancer patients. Methods: Subjects were 17 postmenopausal breast cancer patients (mean age, 63.3 +/- 9.9 years) receiving non-steroidal aromatase inhibitor (AI; anastrozole, 1 mg daily) only and 10 such patients (mean age, 65.0 +/- 5.1 years) receiving AI + bisphosphonate (risedronate sodium, 2.5 mg daily) for 6 months. All of the subjects had undergone surgical resection and had positive estrogen receptor tumor status. Age, age at menopause, years since menopause, height, weight, and body mass index (Wt/Ht(2)) were recorded. Lumbar spine (L2-4) bone mineral density (BMD), T-, and Z-scores were assessed on dual-energy X-ray absorptiometry before and after therapy. Results: In the AI-only group BMD, T-, and Z-scores significantly decreased from the baseline during the 6-month therapy period (P < 0.05). Mean decreases in L2-4 BMD and Z-score were 2.5% and 3.0%, respectively. In the AI + bisphosphonate group, however, BMD, T-, and Z-scores significantly increased from the baseline values (P < 0.01). Mean increases in L2-4 BMD and Z-score were 4.5% and 3.3%, respectively. Conclusions: AI carries a potential risk of bone mineral loss despite the short therapy duration. Bisphosphonate has a preventive effect on this loss.