Background Denosumab (DMAB) withdrawal without subsequent bisphosphonate treatment seems to be related to a rebound effect: a rapid decrease in mineral density in bone densitometry (DEXA). However, evidence is scarce.
Objectives To analyze DEXA values in patients who have stopped DMAB without subsequent treatment and to detect possible factors associated.
Methods Unicentric observational study. We included patients with osteoporosis (OP) who attended our rheumatology clinic from May 2017 to December 2018, who had stopped DMAB without any further treatment. Demographic data, risk factors for OP (smoking, age of menopause, previous fractures, chronic corticotherapy), data related to calcium and vitamin D analogues supplementation, previous OP treatment and durantion of active treatment with DMAB were collected; as well as DEXA data (last DEXA while on DMAB and inmmmediate DEXA after its withdrawal, no more than 3 years later). For the statistical analysis, means, standard deviations, frequencies and percentages are reported accordingly. Paired Student’s T test has been used to analyze medias in both DEXAs, and chi square for comparisons when appropriate.
Results 39 patients (38 women) age 70.17±.4, menopause at 46±4.07 years, 37(94%) never used tobacco, 25 (64%) suffered some fracture before treatment with DMAB, 17(43%) received previous bisphosphonates, 5 (13%) teriparatide and 7(18%) strontium ranelate. The average duration of DMAB use was 2 ±0.86 years, onset at 61 ±7.34 years. Standard deviations (T score) of DEXA values worsened significantly (p <0.001) in all the locations: femur -0.28 (IC95% -0.36 to -0.19), columnL1 -0.43 (IC95% -0.30 a - 0.56), columnL2 -0.44 (IC95% -0.25 to -0.62) columnL3 -0.40 (IC95% -0.22 to -0.59) columnL4 -0.52 (IC95% -0, 33 to -0.72) columnL1-L4 -0.48 (IC95% -0.33 to -0.64) (table 1). We analyzed the decrease in T-scores alongside the other variables, obtaining a proportionally inverse relation between duration of DMAB use and this reduction (table 2). Given that DMAB use in one patient was several standard deviations above the mean (12 yrs), her data where excluded for analysis.
Conclusion DMAB withdrawal without subsequent antiresorptive treatment produces a rapid decrease in DEXA values in our patients. This phenomenon appears to diminish in patients who have received DMAB for a longer period.
References  M. B. Zanchetta, J. Boailchuk,F. Massari,F. Silveira,C. Bogado and J. R. Zanchetta. Significant bone loss after stopping long-term denosumab treatment: a post FREEDOM study. Osteoporos Int(2018) 29:41–47
 Olivier Lamy, Delphine Stoll, Bérengère Aubry-Rozier, Elena Gonzalez Rodriguez. Stopping Denosumab. Current Osteoporosis Reports. Published onlineJan. 2019
 Chapurlat R, Effectsand Management of Denosumab Discontinuation, Joint Bone Spine (2018).
Disclosure of Interests None declared
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