Predictors of denosumab efficacy in treating osteoporosis in patients with rheumatoid arthritis: a Japanese multicenter study

We investigated 2-year outcomes of denosumab treatment for osteoporosis in patients with rheumatoid arthritis (RA) and predictors of good outcomes. Study participants were 74 females treated with denosumab for 24 months. After investigating baseline demographics and overall time course for each patient, we divided all cases into two groups according to percent change (%) in bone mineral density (BMD) of lumbar spine (LS-) and total hip (TH-) at 24 months (-24m); two thirds of the patients were allocated to the good outcome group (LS-GO and TH-GO), and the other third to the non-good outcome group (LS-NG and TH-NG). We performed multivariate analysis to confirm predictors of greater increases in LS- and TH-BMD. LS-BMD-24m and TH-BMD-24m increased significantly from baseline. We observed greater %LS-BMD-24m in LS-GO group than in LS-NG group, while %TH-BMD-24m showed no significant group-dependent difference. N-terminal propeptide of type 1 collagen (P1NP) and tartrate-resistant acid phosphatase (TRACP)-5b decreased more in LS-GO group than in LS-NG group at each time point. We observed greater %TH-BMD-24m in TH-GO group than in TH-NG group, while %LS-BMD-24m showed no significant group-dependent difference. Only P1NP-6m showed a larger decrease in TH-GO group relative to TH-NG group. Multivariate analysis confirmed that the larger decrease in P1NP-6m was associated with the greater increase in LS-BMD-24m, while the combined use of biologics was associated with the greater increase in TH-BMD-24m. In conclusions, denosumab increased BMD in RA patients with osteoporosis. The combined use of biologics and denosumab may provide useful treatment options.