Effect of denosumab on low bone mineral density in postmenopausal Japanese early breast cancer patients receiving aromatase nhibitors: 36-month results

Abstract

Background: Aromatase inhibitors (AI) are standard as postoperative adjuvant therapy for hormone positive postmenopausal breast cancer. In recent years, the administration period tends to be longer, and bone loss which is a side effect has become a serious problem. We have already reported the effect of denosumab up to 24 months on postmenopausal early breast cancer patients with low bone mineral density (BMD) receiving AIs as adjuvant hormonal therapy. BMD in the lumber spine was found to increase, and the combination of denosumab revealed useful for blocking bone mineral loss in Japanese women receiving AIs. Methods: Study design: A non-randomized, prospective study at three institutions was conducted in Japan. Patients administered 60 mg of denosumab subcutaneously every 6 months. The BMD of the lumbar spine and bilateral femoral neck was measured at baseline and at 6, 12, 18, 24, 30 and 36 months. The levels of serum tartrate-resistant acid phosphatase isoform 5b (TRAP5b), bone alkaline phosphatase (BAP), albumincorrected serum calcium concentration was measured at baseline and 1, 6, 12, 18, 24, 30 and 36 months. Patients: Postmenopausal women with early-stage hormone receptorpositive invasive breast cancer who were scheduled to receive an AI as adjuvant hormonal therapy or receiving AI adjuvant therapy were included in the analysis. We also included those who had completed a chemotherapy regimen ≥4 weeks before entering the study and patients with low BMD (lumbar spine, right femoral neck, and left femoral neck BMD:-2.5< T-score