Tumor-Induced Osteomalacia: Experience from a South American Academic Center

Presentation Number: SUN 339
Date of Presentation: April 2nd, 2017

Pablo F Florenzano*1, Rene Baudrand2, Maria F Sepulveda3, Nevenka Vucetich4, Francisco J Guarda2, Pablo Villanueva5, Luis Michea6, Oscar Contreras5 and Gilberto B Gonzalez4
1Pontificia Universidad Católica de Chile, Santiago, Chile, 2Pontificia Universidad Catolica de Chile, Santiago, Chile, 3Pontificia Universidad Catolica, Puerto Montt, Chile, 4Pontificia Universidad Catolica, Santiago, Chile, 5Pontificia Universidad Catolica, 6Instituto de Ciencias Biomédicas, Facultad de Medicina. Universidad de Chile, Las Condes, Chile

Abstract

Context: The vast majority of cases of tumor-induced osteomalacia (TIO) have been reported in the northern hemisphere and Asia. To the best of our knowledge there are no published case series of South American TIO patients originating from a single center.

Objective: Describe the experience of clinical presentation, diagnostic study and treatment of patients with TIO in a South American academic center in comparison to the available literature.

Patients and methods: A retrospective analysis of the records of patients diagnosed with TIO at the Clinical Hospital of the Pontificia Universidad Católica in Santiago, Chile between January 1999 and May 2016 was performed. The clinical presentation, diagnostic studies and treatment were analyzed. Fibroblast growth factor 23 (FGF23) was measured with an immunometric enzyme assay aimed to C-terminal fragment (normal value: ≤180 RU/mL) in 3 cases and by ELISA using the Human Intact FGF-23 (Immunotopics Inc.) in the other 3. (Normal value: 8.2-54.3 pg/ml)

Results: Six patients (3 women and 3 men) were diagnosed with TIO during the studied period. The patients’ median age was 53 years (range 22-64). All patients presented with weakness and diffuse extremity pain. Four experienced multiple fractures during the evolution of their illness. The median time to diagnosis was 4.5 years (1-20). Biochemical studies showed hypophosphatemia, median of 1.4 mg/dl (1.2-1.6), with low maximum rates of tubular reabsorption of phosphate adjusted for glomerular velocity (TmP/GFR), 0.82 mg/dl (0.35-1.25). FGF23 was elevated above the reported normal range in 4/6 patients and inappropriately normal in the other 2. In 3 patients the location of the tumor was clinically evident on physical examination and confirmed with anatomical imaging (MR, CT or US). In the remaining patients, 2 tumors were located with 68Ga DOTATATE PET/CT, and one with scintigraphy with 111In-Pentetrotide (OctreoScan). The causal tumors were located in the lower extremities in 5 patients and in the remaining patient the tumor was invasive rhinosinusal. In all patients, tumors were successfully removed with wide margins. Within 14 days there was normalization of phosphate and FGF23 levels and a complete resolution of clinical symptoms in all patients. In all cases the histopathology was compatible with a phosphaturic mesenchymal tumor.

Conclusions: The clinical presentation, delay time to diagnosis, FGF23 diagnostic performance and histopathology in this first series of South American patients coincides with those of cases described in the literature with other populations. The success of localization by DOTATATE-based imaging, which is available in South America, suggests this may be the superior imaging modality.

 

Nothing to Disclose: PFF, RB, MFS, NV, FJG, PV, LM, OC, GBG