THU462 Clinical Features & Management Of FGF23 Secreting Tumors: Series Of 40 Clinical Cases
Authors: Gronskaia Sofya , Belaya Zhanna , Rozhinskaya Liudmila , Dubovitskaya Tatiana , Mamedova Elizaveta , Pigarova Ekaterina A , Degtyarev Mikhail , Rodionova Svetlana , Buklemishev Yuri , Babaeva Diana , Vladimirova Victoriya , Tarbaeva Natalia , Serzhenko Sergey , Grigoriev Andrey , Dzeranova Larisa , Karpenko Vadim , Karasev Anatoly , Fedotov Roman , Ulyanova Irina , Trukhina Diana , Toroptsova Natalia , Lesnyak Olga , Mokrysheva Natalia G , Melnichenko Galina A , Dedov Ivan 
Published: October 2023

Disclosure: S. Gronskaia: None. Z. Belaya: None. L. Rozhinskaya: None. T. Dubovitskaya: None. E. Mamedova: None. E.A. Pigarova: None. M. Degtyarev: None. S. Rodionova: None. Y. Buklemishev: None. D. Babaeva: None. V. Vladimirova: None. N. Tarbaeva: None. S. Serzhenko: None. A. Grigoriev: None. L. Dzeranova: None. V. Karpenko: None. A. Karasev: None. R. Fedotov: None. I. Ulyanova: None. D. Trukhina: None. N. Toroptsova: None. O. Lesnyak: None. N.G. Mokrysheva: None. G.A. Melnichenko: None. I. Dedov: None.

Introduction: Tumor-induced osteomalacia is an acquired rare disease manifested by hypophosphatemic osteomalacia due to excessive secretion of fibroblast growth factor 23 (FGF23). FGF 23 is a non-classical hormone secreted by bone tissue (osteocytes) and regulates phosphorus metabolism.The aim of this work is to present clinical experience in the diagnosis, treatment and rehabilitation of patients with tumor-induced osteomalacia. Materials and methods: 40 patients with clinically-confirmed tumor-induced osteomalacia were included in the study, 34 of whom had the tumor localized, 27 underwent surgical treatment and 21 achieved stable remission. Results: The average age was 48 +/- 14 years, 43% were men, the time left from the the onset of the disease was 8 +/- 6 years. Biochemical fundings were hypophosphatemia 0.47 [0.4 ; 0.53] mmol/l, a decrease in the tubular reabsorption phosphate 62 [52 ; 67]%, and an increase in alkaline phosphatase of 183 [112 ; 294] units/l. At the time of diagnosis, 100% had multiple pathological fractures, only 10% could move independently, and 76.3% classified the pain as unbearable (8-10 points according to the 10-point pain syndrome scale ). Among the methods used to detect tumors, the most sensitive were scintigraphy with tectrotide with SPECT/CT 71.4% (20/28) and MRI 90% (18/20). In 55% of cases, the tumor was localized in soft tissues and in 45% in bone tissue; The tumor was most often detected in the lower extremities, followed by the head in frequency of localization. 18 patients currently have no remission and they receive conservative treatment (phosphorus and alfacalcidol n=15 and burozumab n=3). In case of achieving remission (n=21), regression of clinical symptoms and restoration of bone and muscle mass was observed. Extensive excision of the tumor without prior biopsy resulted in the best percentage of remission - 87%. Conclusion: Tumor-induced osteomalacia is most common in the middle age people. It is characterized by severe damage to bone and muscle tissue with the development of multiple fractures, muscle weakness and severe pain syndrome. In laboratory diagnostics, attention should be paid to hypophosphatemia, a decrease in the tubutar reabsorption phosphate index and increased alkaline phosphatase. The use of functional diagnostic methods with a labeled somatostatin analogue to the subtype 2 receptor and MRI with contrast enhancement are the most accurate methods of topical diagnostics. In case of localization of the tumor, a wide excision without a preliminary biopsy is recommended.

Presentation: Thursday, June 15, 2023