Tumor-induced osteomalacia: experience from three tertiary care centers in India

• Published in: Endocrine Connections 2019-03, Vol.8 (3), p.266-276
• Main Authors: Pal, Rimesh, Bhadada, Sanjay Kumar, Singhare, Awesh, Bhansali, Anil, Kamalanathan, Sadishkumar, Chadha, Manoj, Chauhan, Phulrenu, Sood, Ashwani, Dhiman, Vandana, Sharma, Dinesh Chandra, Saikia, Uma Nahar, Chatterjee, Debajyoti, Agashe, Vikas
• Format: Article
• Language: English
• Subjects: FGF23; hypophosphatemia; phosphaturic mesenchymal tumor; tumor-induced osteomalacia
• ISSN: 2049-3614; 2049-3614
• DOI: 10.1530/EC-18-0552

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by recalcitrant hypophosphatemia. Reports from the Indian subcontinent are scarce, with most being single center experiences involving few patients. Herein, we conducted a retrospective analysis of 30 patients of TIO diagnosed at three tertiary care hospitals in India. Patients with persistent hypophosphatemia (despite correction of hypovitaminosis D), normocalcemia, elevated alkaline phosphatase, low TmP/GFR and elevated or ‘inappropriately normal’ FGF23 levels were labeled as having TIO. They were sequentially subjected to functional followed by anatomical imaging. Patients with a well-localized tumor underwent excision; others were put on phosphorous and calcitriol supplementation. The mean age at presentation was 39.6 years with female:male ratio of 3:2. Bone pain (83.3%) and proximal myopathy (70%) were the chief complaints; 40% of cases had fractures. The mean delay in diagnosis was 3.8 years. Tumors were clinically detectable in four patients (13.3%). The mean serum phosphate was 0.50 mmol/L with a median serum FGF23 level of 518 RU/mL. Somatostatin receptor-based scintigraphy was found to be superior to FDG-PET in tumor localization. Lower extremities were the most common site of the tumor (72%). Tumor size was positively correlated with serum FGF23 levels. Twenty-two patients underwent tumor resection and 16 of them had phosphaturic mesenchymal tumors. Surgical excision led to cure in 72.7% of patients whereas disease persistence and disease recurrence were seen in 18.2% and 9.1% of cases, respectively. At the last follow-up, serum phosphate in the surgically treated group was significantly higher than in the medically managed group.