Alendronate after denosumab discontinuation in women previously exposed to bisphosphonates was not effective in preventing the risk of spontaneous multiple vertebral fractures: two case reports.

At denosumab discontinuation, an antiresorptive agent is indicated to reduce the high bone turnover, the rapid bone loss, and the risk of spontaneous vertebral fractures. We report two cases of postmenopausal women, previously exposed to bisphosphonates, treated with alendronate at denosumab discontinuation. Alendronate was ineffective to avoid spontaneous clinical vertebral fractures. They presented three and nine spontaneous vertebral fractures 8 and 12 months after denosumab discontinuation, respectively. Ineffectiveness of alendronate was attributed to insufficient control of the rebound as assessed by B-crosslaps measures in the first case, and partially to the high risk of fractures in the later. In both situations, the increased fracture risk may have favoured these new fractures. It is urgent to define effective therapeutic strategies to avoid spontaneous vertebral fractures after denosumab discontinuation.