Background: The discontinuation of treatment with denosumab (Dmab) has been associated with a reactivation effect of bone metabolism that manifests itself with a loss of bone mass and an increased risk of vertebral fractures (VF). The incidence and risk factors that may lead to such loss are not clearly established.

Objectives: Determine the incidence of VF and bone loss in patients who have withdrawn treatment with Dmab and objectify possible associated risk factors.

Methods: Retrospective review study of patients treated with Dmab and monitored the last two years in monographic osteoporosis consultations. . We selected patients who withdrew treatment with Dmab and registered demographic characteristics, risk factors for osteoporosis and densitometries prior to treatment and during the period of suspension. We identified patients who presented fractures during treatment withdrawal period, assessing: number of fractures, time from withdrawal to fracture presence, location and if they had received osteoactive treatment in that period.

Results: Of 415 patients treated with Dmab, 83 discontinued treatment. The average age was 63.91 years, 95.2% of them women. The average duration of treatment prior to withdrawal was 2.73 years. 43.4% of the patients had previous fractures, 47.2% vertebral. The data of the previous bone mineral density and during the follow-up are shown in Table 1 . 60 patients presented risk factors for osteoporosis, the most frequent being low calcium intake (36.6%) and 15.6% had disease and osteopenizing treatment. 92.7% of the patients had received prior osteoactive treatment. The most frequent reason for withdrawal of Dmab was for therapeutic vacations (56.6%). 39 patients performed post-withdrawal osteoactive treatment, mostly zoledronate (51.3%). During the two years after the rest, 9 patients had fractures (10.9%), seven of vertebral location (77.7%) and ≥ 2 VF were observed in five of them. 5 patients (71.4%) already had fractures prior to the onset of Dmab. The average time from withdrawal from treatment to fracture presentation was 15 months. None of the fractured patients had received treatment after Dmab withdrawal. Although the mean BMD analyzed by DXA at the end of treatment and that the loss of BMD during rest was higher in patients with fracture compared to those without fracture (-7.8% vs -4.3% in the spine and -8.6% vs -4.4% in total femur), the differences were not significant.

Conclusion: The incidence of VF in patients who interrupted Dmab was 8.43%. Fractured patients had lower BMD gain despite the treatment than non-fractured patients and also the loss of BMD at rest was greater, without significant differences probably due to low number of patients. Neither the presence of previous fractures nor the duration of treatment could be related to the presence of VF at rest.

Disclosure of Interests: None declared