Effects of Sequential Anti-Resorptive Agents on Bone Mineral Density Following Denosumab Withdrawal: A Multicenter Real-World Study in Korea (MAXCARE Study)

Background: Denosumab is a potent anti-resorptive agent widely used for osteoporosis. However, its discontinuation results in a ‘rebound phenomenon’ of rapid bone loss, necessitating transition to alternative anti-resorptive therapies. Despite this, there is limited evidence to guide the selection of the most effective agent, particularly among bisphosphonates. This study aimed to evaluate the efficacy of different anti-resorptive therapies following denosumab discontinuation in a real-world clinical setting. Methods: This retrospective study included 360 patients (low-dose alendronate/calcitriol combination [MXM, n=118], alendronate [ALD, n=53], risedronate [RIS, n=20], ibandronate [IBN, n=30], zoledronic acid [ZOL, n=106], selective estrogen receptor modulator [SERM, n=33]) who received at least 12 months of post-denosumab anti-resorptive therapy. Bone mineral density (BMD) changes from baseline and fracture patterns were assessed over the treatment period. Results: Baseline characteristics, including age and body mass index, were comparable across groups, with an average of 4.2 denosumab administrations per patient. The SERM group experienced the greatest BMD decline across all sites. Significant BMD reductions in the lumbar spine and femoral neck and in the femoral neck alone were observed in the IBN and RIS groups, respectively. While BMD decline was also observed in the MXM, ALD, and ZOL groups, these changes were not statistically significant. Conclusion: MXM, ALD, and ZOL mitigated BMD loss following denosumab discontinuation. Conversely, RIS, IBN, and SERM did not adequately prevent BMD decline. These findings underscore the importance of selecting the most appropriate sequential anti-resorptive therapy in clinical practice to minimize BMD loss and reduce the risk of adverse outcomes.