Endocrine Abstracts

Denosumab discontinuation (DD) induces an increase of B-crosslaps above baseline values for two years, and a decrease of BMD values. This rebound effect is associated with spontaneous clinical vertebral fractures (SCVF) in close to 15% of patients considering a follow-up of 2 years without taking another osteoporosis treatment. We report the clinical characteristics of 31 patients evaluated at our center from July 2015 to January 2018.

Results: Thirty women and one man, 62.8±10.1 years, experienced 145 SCVF (median 5) in the 11.7±3.0 months (median 11; min 7, max 20) following the last denosumab injection. They received 6.4±2.7 denosumab injection (min 2; max 11). Ten women had vertebroplasties with 22 new SCVF in the following days. Nine women received aromatase-inhibitors (AI) with denosumab. Eight women had prevalent VF, five received bisphosphonate before denosumab. The mean B-crosslaps value at the time of SCVF was 1511±573 μg/l; B-crosslaps values increase with the number of denosumab doses (P=0.05) and decrease with age (P<0.01). The number of SCVF was inversely associated with age (P<0.004). Before the vertebroplasty, the mean number of SCVF was 5.1±3.0 vs 2.3±1.5 in women <65 vs >65 years. The delay between DD and the occurrence of SCVF increases with age: 10.6±1.6 vs 13.3±3.8 months, before vs after 65 years (P<0.01). The mean reasons for DD were: end of AI or no more osteoporosis (15), omission (7), patient’s wish (5), AFF or dental intervention (4).

Conclusion: The SCVF are a very severe and frequent clinical complication occurring after DD. A close follow-up during 2 years post DD is necessary. Studies are urgently needed to better define the place of denosumab in osteoporosis treatment, and the strategies to avoid these side effects.