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 (18F‐FDG PET/CT, 99Tc‐HYNIC‐TOC SPECT/CT and 68Ga‐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 99Tc‐HYNIC‐TOC SPECT/CT (six of six patients) and 100% for 68Ga‐DOTATATE PET/CT (seven of seven patients). Of nine patients, six were subjected to both the 99Tc‐HYNIC‐TOC SPECT/CT and 68Ga‐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 18F‐FDG PET/CT in tumour localization. Amongst the somatostatin receptor‐based scans, 99Tc‐HYNIC‐TOC SPECT/CT and 68Ga‐DOTATATE PET/CT performed equally well for localization of tumours.