Risk Factors for Non-Response to 2 Years of Denosumab Administration in Patients with Osteoporosis: a retrospective cohort study

Background: To investigate the factors associated with changes in bone mineral density and the incidence of fractures in osteoporotic patients treated with denosumab. Methods: : This retrospectively registered study included 162 osteoporotic patients treated with denosumab for 24 months between 2013 and 2019. Patients were divided according to the changes in BMD as non-responders (NL group: <3% increase in lumbar spine BMD [LBMD], NH group: <0% increase in femoral neck BMD [HBMD]) or responders (RL group: ≥3% increase in LBMD, RH group: ≥0% increase in HBMD). Results: : The respective changes in the LBMD and HBMD after 24 months of denosumab treatment were 9.3% (95% confidence interval (CI): 8.1–10.6) and 3.3% (95% CI: 2.1–4.5). Twenty-eight (15.3%) patients were in the NL group, and 134 (82.7%) were in the RL group. A history of bisphosphonate treatment was a risk factor for being in the NL group (odds ratio [OR]: 3.84, 95% CI: 1.38–10.71, p=0.007; adjusted OR: 3.21, 95% CI: 1.01–10.19, p=0.048). Although the NH and RH groups had similar baseline characteristics, the NH group had a significantly higher baseline HBMD than the RH group (p=0.003). The change in HBMD was negatively associated with the HBMD at baseline (r=-0.34, p<0.001). No new osteoporotic fractures occurred in either group during follow-up. Conclusion: In osteoporotic patients receiving denosumab treatment, a history of bisphosphonate treatment was a risk factor for a lack of increase in LBMD, and a higher HBMD at baseline was negatively associated with the change in HBMD.