Denosumab effect on bone mineral density and urinary-NTX in breast cancer patients receiving aromatase inhibitors

IntroductionAromatase inhibitors are used post-surgical intervention in postmenopausal patients with breast cancer. However, these drugs accelerate decline in bone mineral density (BMD), which is countered by use of denosumab, and the efficacy of the drug can be assessed by bone turnover markers. We investigated the effects of denosumab administration for 2 years on BMD and urinary N-telopeptide of type I collagen (u-NTX) levels in breast cancer patients treated with aromatase inhibitors.Materials and methodsThis was a single-center retrospective study. Postoperative hormone receptor-positive breast cancer patients with low T-scores biannually received denosumab from the time of initiation of aromatase inhibitor therapy for 2 years. BMD was measured every 6 months, and u-NTX levels were assessed after 1 month and thereby every 3 months.ResultsThe median patient age of the 55 patients included in this study was 69 (range: 51-90) years. BMD gradually increased in the lumbar spine and femoral neck and u-NTX levels were lowest at 3 months post-initiation of therapy. Patients were divided into two groups based on the change ratio of u-NTX 3 months post-denosumab administration. Of these, the group with higher change ratio showed a higher degree of BMD restoration in the lumbar spine and femoral neck 6 months post-denosumab treatment.ConclusionDenosumab increased BMD in patients treated with aromatase inhibitors. The u-NTX level decreased soon after start of denosumab treatment, and its change ratio is predictive of improvement in BMD.