OR13-06 Romosozumab After Denosumab Improves Lumbar Spine Bone Mineral Density And Microarchitecture Greater Than Denosumab Continuation In Postmenopausal Women

Disclosure: N. Hong: None. S. Shin: None. H. Kim: None. Y. Rhee: None. Transitioning to romosozumab from antiresorptives can be an effective strategy to improve bone strength. A phase 2 trial and a few observational studies showed improvement of lumbar spine bone mineral density (BMD) with maintained hip bone density by romosozumab after denosumab. However, whether transition to romosozumab after denosumab is associated with greater improvement in BMD and microarchitecture compared to denosumab continuation remains unclear. In this propensity score-matched cohort study, we analyzed data from postmenopausal women who initiated denosumab between 2017 and 2020 (at least two injections; n=696). Individuals who were transited to 12 months of romosozumab after denosumab (n=105) were 1:1 matched to those who continued denosumab (n=591) by propensity score using age (69 years), body mass index, BMD, and numbers of denosumab injection at the time of transition, BMD improvement during denosumab treatment, prior fracture and bisphosphonate use (n=93 for each; denosumab-romosozumab [DR] and denosumab-denosumab [DD]). BMD gain by denosumab in DR and DD groups from denosumab initiation to transition time (to romosozumab or denosumab continuation; median 4 times [range 2 to 8] of denosumab injection) was +4.6% and +2.4% in the lumbar spine (LS, T-score −3.4 to −3.1) and total hip (TH, T-score −2.5 to −2.4), without statistical difference. DR group showed greater LSBMD gain compared to the DD (+7.0% vs. +2.5%, P<0.001) during 12 months after the transition time, yielding greater net LSBMD gain in DR (median 2 years of denosumab followed by 1-year romosozumab) compared to DD (median 3 years of denosumab; +11.6% vs. +7.0%, P<0.001). Differences in LSBMD gain between DR and DD groups remained robust (adjusted difference +4.7% point, P<0.001) after adjustment for covariates. Hip BMD changes did not differ between DR and DD (DR vs. DD; FN, +1.3% vs. +2.0%, p=0.409; TH, -0.9% vs. +0.2%, P=0.132). DR group showed significant improvement in the trabecular bone score during romosozumab use (1.288 to 1.311, p=0.005), whereas denosumab continuation in the DD group did not (1.297 to 1.309, p=0.103). During 12 months, one incident morphometric vertebral fracture (grade 1) and one nonvertebral fracture (patella) were observed in DD, whereas one ankle fracture was observed in the DR group. In summary, romosozumab after denosumab improved lumbar spine BMD and microarchitecture greater than denosumab continuation, with the maintenance of hip BMD. Presentation: Friday, June 16, 2023