%0 Journal Article
%T A retrospective cohort of tumor-induced osteomalacia and case series of malignant disease.
%A Hoong CWS
%A Sfeir J
%A Algeciras-Schimnich A
%A Clarke BL
%J J Clin Endocrinol Metab
%V 0
%N 0
%D 2024 Mar 20
%M 38506445
%F 6.134
%R 10.1210/clinem/dgae183
%X OBJECTIVE: We aimed to describe the clinical characteristics of a large cohort of patients diagnosed with tumor-induced osteomalacia (TIO), with a focus on patients with non-localizing and malignant TIO.
METHODS: This is a retrospective cohort of TIO patients in an academic medical center, diagnosed between January 1998 to May 2023. We described their demographics, biochemistries, tumor features, localization, treatment and complications.
RESULTS: Of 68 patients diagnosed with TIO, 49 (72%) were localizing and 5 (7.4%) were malignant. Of 50 patients who attempted localizing procedures, 29 (58%) achieved cure. 20 (40%) had persistent disease due to wrong tumor targeted, or refractory or recurrent tumors, despite up to 6 procedural attempts. There was no difference in demographics, phosphorus or baseline fibroblast growth factor-23 (FGF23) levels between localizing versus non-localizing groups, and malignant versus non-malignant groups. Lower extremity was the commonest site of localization (37%), with 47% in bone and 53% in soft tissue. 60% of malignant cases were located in the trunk. Tumor size correlated with peak FGF23 (R=0.566, p<0.001) but was not associated with malignancy risk (p=0.479). A cut-off FGF23 of >20 times upper limit of normal in the presence of normal renal function (p=0.025), and recurrence after initial cure (p=0.013) were factors significantly associated with malignancy. The non-localizing group had lower survival than localizing group (p=0.0097).
CONCLUSIONS: TIO is a condition with significant morbidity. Very high FGF23 level and disease recurrence are associated with malignant disease. Reasons behind the observation of higher mortality in non-localizing TIO should be further explored.