Risk factors for poor response to denosumab treatment in Japanese postmenopausal women with osteoporosis

Introduction Denosumab has been reported to increase bone mineral density (BMD) and suppress fractures, but poor responders are not uncommon. This study aimed to identify risk factors for poor response to denosumab treatment. This is the first study to explore risk factors for poor response to denosumab. Materials and methods This retrospective observational study investigated 227 Japanese postmenopausal women who received denosumab with monitoring of BMD by dual-energy X-ray absorptiometry at 6-month intervals. Risk factors were identified using Cox's proportional hazard modeling. Poor responders were defined as not exceeding the least significant change of BMD from baseline for 3 years. Results Mean relative change from baseline for 3 years in lumbar spine (LS)-BMD, femoral neck (FN)-BMD, and total hip (TH)-BMD were 12.6%, 6.8%, and 6.1%, respectively. Numbers of poor responders were 10 in LS-BMD, 47 in FN-BMD, 38 in TH-BMD. Risk factors for poor response were concomitant glucocorticoid use for LS-BMD, low body mass index or initiation at higher BMD for FN-BMD, and pretreatment with bisphosphonates or initiation at higher BMD for TH-BMD. Conclusion Risk factors for insufficient denosumab effect differed between BMD measurement sites. These results should be taken into consideration when selecting denosumab in clinical practice.