Antiresorptive activity of denosumab in the treatment of osteoporosis in patients with rheumatoid arthritis

Background : fracture risks assessment and determination of bone mineral density are modern methods, generally accepted and widely used. However, they have limitations and disadvantages for the dynamic evaluation of bone remodeling processes in RA-patients with low BMD. The investigation of bone resorption markers is an important issue. Aims : to compare the antiresorptive activity of denosumab and alendronic acid in patients with rheumatoid arthritis and osteoporosis using β-CTX and osteocalcin (OC). Materials and methods : forty-two patients were included in the study (16 patients were treated with denosumab, 13 patients – with alendronic acid, 13 patients - control group without any osteoporosis treatment). The quantitative determination of β-CTX and OC as well as dual-energy X-ray absorptionometry (DXA) were carried out for all patients at the first visit with consecutive investigation of bone resorption markers 3 months after. The predictive capacity was determined using the ratio of observed fractures/expected fractures by FRAX. Results : The level of β-CTX 16% (median 861.6 pg/ml vs. 724.6 pg/ml, p = 0.049) and OC 39% (median 13.9 ng/ml vs 8.5 ng/ml, p = 0.047) decreased significantly in 3 month in RA patients treated with denosumab. The decrease of β-CTX (median 858.9 pg/ml vs. 821.8 pg/ml) and OC (median 14.8 ng/ml vs. 13.9 ng/ml) was observed in the group of patients treated with alendronic acid, but not reached statistical significance. Conclusions : denosumab had showed better antiresorptive activity compared with bisphosphonates, which was registered 3 month after the start of the treatment.