Functional imaging in primary tumour‐induced osteomalacia: relative performance of FDG PET/CT vs somatostatin receptor‐based functional scans: a series of nine patients

Context Localization of phosphatonin‐producing mesenchymal tumours in patients with primary tumour‐induced osteomalacia ( pTIO ) is challenging. Functional imaging plays an important role in the localization of these tumours. Objective We studied the relative performance of different functional imaging modalities ( 18 F‐ FDG PET / CT , 99 Tc‐ HYNIC ‐ TOC SPECT / CT and 68 Ga‐ DOTATATE PET / CT ) in tumour localization in cases of pTIO . Design and Methods Retrospective chart evaluation of 16 patients with confirmed TIO treated from 2006 to 2013 was conducted in a tertiary care referral centre. Results Of 16, nine patients had pTIO . In these nine, the positivity rates of different functional imaging modalities were 50% for 18 F‐ FDG PET / CT (four of eight patients), 100% for 99 Tc‐ HYNIC ‐ TOC SPECT / CT (six of six patients) and 100% for 68 Ga‐ DOTATATE PET / CT (seven of seven patients). Of nine patients, six were subjected to both the 99 Tc‐ HYNIC ‐ TOC SPECT / CT and 68 Ga‐ DOTATATE PET / CT and all of them showed coregistration on the two scans. Conclusions In patients with pTIO , the somatostatin receptor‐based functional scans performed better than 18 F‐FDG PET/CT in tumour localization. Amongst the somatostatin receptor‐based scans, 99 Tc‐ HYNIC ‐ TOC SPECT / CT and 68 Ga‐ DOTATATE PET / CT performed equally well for localization of tumours.