Clinical Features, Tumour Localization and Prognosis in a Cohort of Patients with Tumour Induced Osteomalacia (TIO)

Presentation Number: SUN 340
Date of Presentation: April 2nd, 2017

Eesh Bhatia*1, Aditi Chopra2, Ravina Mudalsha2, Sanjay Gambhir2, Sushil Gupta2, Preeti Dabadghao2 and Subhash B Yadav2
1Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow UP, INDIA, 2Sanjay Gandhi Postgraduate Institute of Medical Sciences

Abstract

Background: Tumour-induced osteomalacia (TIO) is a rare but curable cause of renal phosphate wasting and osteomalacia, resulting predominantly from small mesenchymal tumours. The presentation may be delayed and localization of tumours is difficult resulting in poor outcomes after surgery.

Objective: To describe the clinical presentation, localization using Ga-68 DOTANOC PET/CT scan, and follow up of Indian patients with TIO.

Patients and Methods: Nineteen patients [13 males; age (mean ± SD) 43 ± 14 years] with suspected TIO were managed in our department between 1998- 2016. Their clinical and biochemical details, imaging modalities, surgical interventions (if any) and outcomes are reviewed.

Results: The median duration of symptoms prior to diagnosis was 4 (range 1-15) years. All patients had severe disability due to pain and proximal muscle weakness at presentation. Pathological fractures (47%) and bony deformities (42%) were frequent. C-terminal FGF-23 was elevated in all 18 patients tested. The tumour was successfully localized in 12/19 patients (63%). Tumours were located in the extremities (5 in lower limb, 3 in upper limb), head and neck region (n=3) and mediastinum (1). Of the 16 patients who underwent Ga68 DOTANOC PET/CT, tumour was detected in 9 (56%) patients. Patients with localized scans had higher FGF-23 levels (2235+735 RU/ml) compared with non-diagnostic scans (403+153 RU/ml, p=0.02), though other clinical features did not differ. FGF-23 levels were correlated with standardized uptake value (SUV) on the Ga-68 scan (r=0.78, p=0.02). Sequencing of the FGF23 gene ruled out late-onset autosomal dominant hypophosphatemic osteomalacia in all patients in whom tumours were not localized. Despite complete resection of the tumour and biochemical recovery in 7 patients, skeletal deformities persisted in most patients. Three patients could undergo only partial resection, with severe bone deformities precluding complete resection in 2 cases.

Conclusions: Most patients presented late with multiple fractures and deformities. Using Ga-68 DOTANOC PET/CT, tumour was localized in 56% of patients. Patients with unsuccessful localization had lower FGF-23 levels compared with those in whom tumour was detected.

 

Nothing to Disclose: EB, AC, RM, SG, SG, PD, SBY