Clinical Profile and Treatment Outcomes of Tumour-Induced Osteomalacia - A Single-Centre Experience.

Abstract

Introduction: Tumour-induced osteomalacia (TIO) is rare. At our referral centre, we see a substantial number of TIO. Therefore, we planned to study their profile and treatment outcomes to provide insight in management.

Methods: This ambispective study evaluated 43 patients with TIO treated at our centre (2014-2024). Patients were grouped into (a) Localised TIO (n = 31; histopathology suggesting phosphaturic mesenchymal tumour or disease remission and (b) Unlocalised TIO (n = 12; occult tumour and negative genetic testing for hereditory hypophosphatemic disorders).

Results: The mean age of participants was 40.9 ± 13.4 years. The median diagnostic delay was 3 years from symptom onset. Bone pain, muscle weakness, fractures, teeth loss, and palpable lump were presenting features. Two had intact fibroblast growth factor 23 (iFGF23) in normal range. No significant clinical bias existed between tubular maximum reabsorption of phosphate/glomerular filtration rate (TmP/GFR) calculated using second void urine and 24-h urine samples. The most common location was lower limbs (41.9%), followed by head and neck (32.3%). Tracer avid lesions on Ga-68-DOTANOC-positron emission tomography/computed tomography (PET/CT) were noted in 30/43 (69.8%) patients. Of the 13 patients negative on somatostatin receptor-based imaging, only one showed tracer avid lesion on F-18-fluorodeoxyglucose-PET/CT scan. Disease remission was documented in 19/24 (79.2%) patients undergoing surgical excision and 1/5 (20%) treated with radiofrequency ablation. After successful intervention, plasma iFGF23 levels normalised by Day-3, tubular reabsorption of phosphate and TmP/GFR by Day-4, and serum phosphate by Day-7. No patient with remission experienced relapse at a median follow-up of 4.25 years.

Conclusion: Ga-68-DOTANOC-PET/CT picked up maximum lesions, F-18-FDG-PET/CT picked up one additional lesion. Surgery was curative in most. Post successful intervention, iFGF23 normalised in all by the third day.