Long-term effect of denosumab on bone microarchitecture as assessed by tissue thickness-adjusted trabecular bone score in postmenopausal women with osteoporosis: results from FREEDOM and its open-label extension.

ABSTRACT

In postmenopausal women with osteoporosis, up to 10 years of denosumab treatment significantly and continuously improved bone microarchitecture assessed by tissue thickness-adjusted trabecular bone score, independently of bone mineral density. Long-term denosumab treatment decreased the number of high fracture-risk patients and shifted more patients to lower fracture-risk categories. PURPOSE: To investigate the long-term effect of denosumab on bone microarchitecture assessed by tissue thickness-adjusted trabecular bone score (TBSTT) in post-hoc subgroup analysis of FREEDOM and open-label extension (OLE). METHODS: Postmenopausal women with lumbar spine (LS) or total hip BMD T-score <-2.5 and ≥-4.0 who completed the FREEDOM DXA substudy and continued in OLE were included. Patients received either denosumab 60 mg subcutaneously every 6 months for 3 years and same-dose open-label denosumab for 7 years (long-term denosumab; n=150) or placebo for 3 years and open-label denosumab for 7 years (crossover denosumab; n=129). BMD and TBSTT were assessed on LS DXA scans at FREEDOM baseline, month 1, and years 1-6, 8, and 10. RESULTS: In long-term denosumab group, continued increases from baseline to years 4, 5, 6, 8, and 10 in BMD (11.6%, 13.7%, 15.5%, 18.5%, and 22.4%) and TBSTT (3.2%, 2.9%, 4.1%, 3.6%, and 4.7%) were observed (all P < 0.0001). Long-term denosumab treatment decreased the proportion of patients at high fracture-risk (according to TBSTT and BMD T-score) from baseline up to year 10 (93.7 to 40.4%), resulting in increases in the proportions at medium-risk (6.3 to 53.9%) and low-risk (0 to 5.7%) (P < 0.0001). Similar responses were observed in crossover denosumab group. Changes in BMD and TBSTT were poorly correlated during denosumab treatment. CONCLUSION: In postmenopausal women with osteoporosis, up to 10 years of denosumab significantly and continuously improved bone microarchitecture assessed by TBSTT, independently of BMD, and shifted more patients to lower fracture-risk categories.