POS0496 MANAGEMENT OF OSTEOPOROSIS IN PATIENTS WITH SYSTEMIC MASTOCYTOSIS: A MONOCENTRIC EXPERT CENTRE EXPERIENCE

Background Systemic mastocytosis (SM) is a rare clonal mast cell disease, associated with vertebral osteoporosis (OP) in ~30% of the patients. This OP frequently leads to multiple fractures, particular young or premenopausal To date, experts field recommend use bisphosphonates as first line therapy [1], alternatively interferon alfa [2]. However, data regarding treatments efficacy, and optimal strategy are scarce. Especially, usefulness mastocytosis-specific still be established. Objectives evaluate clinical densitometric efficacy various treatment regimen for osteoporosis, over 1 year, patients systemic mastocytosis. Methods We retrospectively analysed demographic, (including new fragility fractures occurrence), biological from our expert centre (CEREMAST), 2010 2022. All fulfilled WHO criteria had defined either history fracture T-score <-2.5 SD. evaluated bone mineral density (BMD) by DXA, occurrence fracture, at initiation after year exposure following SM-related osteoporosis: 2a (IFN), combination & monthly pamidronate (IFN+PAM), (PAM, 4 patients, quarterly 1), masitinib (MASI), midostaurin (MIDO). IFN+PAM was proposed preferentially severe fractures. PAM case refusal IFN, contra-indication additional cause which IFN would not relevant. Values reported mean (+/-SD). Least significant change BMD 0.03 g/cm². Baseline year-1 were compared paired t-test. A p-value <0.05 considered significant. Results included 37 osteoporotic SM. Thirty-four an indolent SM, SM haematological neoplasm, 2 aggressive form. The age diagnosis 53.5 (+/-12.7) years, 54.1% women. Mean lumbar -2.4 (+/-1.7). hip -1.8 (+/-0.8). Importantly, 81.1% among them 96.6% number 3.6 (+/-3.1) per patient. Two exposed 21 IFN+PAM, 5 PAM, MASI, 9 MIDO. Among treated MIDO, prior IFN+PAM. One patient MIDO group MASI concomitantly (respectively alendronate zoledronate). Regarding significantly improved (see Figure 1). developed during follow-up, 6- 8-months post-treatment initiation. these 7 treatment. Conclusion Our show that pamidronate, improve may reduce risk Conversely, do support monotherapy preferred osteoporosis. Usefulness masitinib, recent tyrosine kinase inhibitors needs further studies this population. References [1]Rossini, M., et al., Prevalence, pathogenesis, options mastocytosis-related Osteoporos Int, 2016. 27(8): p. 2411-21. [2]Laroche, Interferon alpha secondary Am J Med, 2011. 124(8): 776-8. Acknowledgements: NIL. Disclosure Interests None Declared.