206PEffect 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), albumin-corrected serum calcium concentration was measured at baseline and 1, 6, 12, 18, 24, 30 and 36 months. Patients: Postmenopausal women with early-stage hormone receptor-positive 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 Results A total of 103 patients were enrolled. Seventy-three patients completed the study. At 36 months, the BMD of the lumbar spine increased by 8.8%. The BMD of the right and left femoral neck increased by 4.4% and 2.7%, respectively. Symptomatic clinical fractures did not occur in patients receiving AI and denosumab. Conclusions At 36 months, as with the data to the previous 24 months, in combination of denosumab for Japanese women receiving adjuvant AI treatment, an increase in BMD was noted. Clinical trial identification UMIN-CTR, UMIN 000016173. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure T. Taguchi: Research grant / Funding (institution): Chugai Pharmaceutical Co., Ltd.; Research grant / Funding (institution): Taiho Pharmaceutical Co., Ltd.; Research grant / Funding (institution): Daiichi Sankyo Co., Ltd.; Research grant / Funding (institution): Eisai Co. Ltd. All other authors have declared no conflicts of interest.