Endocrine Abstracts

Objective: Limited data suggest that the rebound increase in bone resorption and rapid bone mineral density (BMD) decline following sudden interruption of denosumab therapy can be avoided in patients previously treated with bisphosphonates. We aimed to compare BMD changes in osteoporotic patients after denosumab discontinuation regarding their previous bisphosphonate (BP) therapy.

Material and methods: There were 14 women (age 69 years, BMI 23.1 kg/m² on average) with postmenopausal osteoporosis who had been treated between 2011 and 2015 with denosumab for 2.8 (1–4) years at our outpatient clinic and were not prescribed with another antiresorptive after denosumab discontinuation. Before starting denosumab ten patients were on BP therapy, while the others were treatment naïve. One patient had a history of multiple vertebral fractures and two patients had sustained nonvertebral fractures. There were no fractures during denosumab therapy. BMD was measured at lumbar spine (LS), total hip (TH) and femoral neck (FN) by DXA when denosumab was stopped and 12 to 18 months later. The data were analyzed using exact nonparametric tests.

Results: At the time of denosumab discontinuation 5 patients (36%) were vitamin D sufficient (25OH vitamin D > 75 nmol/l). BMD decreased on average statistically significantly at all sites, (marginally at LS and most clearly at FN). There were no statistically significant differences in average BMD decrease with respect to previous BP therapy. However, there was statistically significantly lower decrease at LS on average among the vitamin D sufficient patients. Off denosumab, one treatment naïve patient and one former BP user sustained five and four vertebral fractures, respectively. Fractures were confirmed with MRI and occurred approximately 13 months after last denosumab dose. The estimated proportion of patients with fractures (adjusted Wald method) was 19% (95% CI 3–41%).

Conclusion: After stopping denosumab BMD similarly decreased in all patients, regardless of previous BP use.