Comparative effects of denosumab or bisphosphonate treatment on bone mineral density and calcium metabolism in postmenopausal women

OBJECTIVES To clarify potential differences between denosumab (DNS) and bisphosphonates (BIS) in terms of bone density and bone metabolism, in a sample of postmenopausal women. METHODS A total of 113 postmenopausal women aged 53-66 years were treated with either DNS or BIS for 12 months. Bone densitometry and laboratory tests were compared between baseline and follow-up. RESULTS Femoral neck BMD increased in both treatment-arms (FN-BMD, DNS: 0.69±0.07 g/cm2 to 0.75±0.09 g/cm2; BIS: 0.69±0.06 g/cm2 to 0.71±0.07 g/cm2; p≤0.001 in both cases). Lumbar spine BMD (LS-BMD) increased significantly only in the DNS-group (0.83±0.14 g/cm2 to 0.89±0.14 g/cm2, p=0.0001). Only women under treatment with DNS had a significant increase in serum parathyroid hormone (PTH: 44.87±17.54 pg/mL to 53.27±15.77 pg/mL, p=0.04), independently of baseline vitamin D levels. DNS-administration resulted in higher increase from baseline in FN-BMD compared to BIS (DNS vs BIS: 8.7%±8.5 vs 3.8%±7.3, p=0.004). Finally, baseline 25OH vitamin D levels did not determine the extent of PTH-increase following administration of DNS- or BIS-treatment. CONCLUSIONS Both treatments increased BMD, however, the effect of DNS on FN-BMD was superior compared to that of BIS. DNS-treatment increased serum PTH. Baseline 25OH vitamin D levels did not predict the extent of PTH increase at follow-up.