Diagnostic efficiency of 68Ga-DOTANOC PET/CT in patients with suspected tumour-induced osteomalacia

Objectives Currently, the main challenge in tumour-induced osteomalacia (TIO) is the difficulty in locating culprit tumours for definitive diagnosis and surgical therapy. Herein, we retrospectively evaluate the efficiency of 68 Ga-DOTANOC PET/CT in the localisation and diagnosis of TIO, and compared with 18 F-FDG. Methods Twenty-four consecutive patients with hypophosphataemic osteomalacia (HO) and suspicion of TIO who were referred to our centre for 68 Ga-DOTANOC PET/CT scanning were retrospectively reviewed. The images were evaluated qualitatively as well as semi-quantitatively, and imaging results were compared with the final diagnoses. Results Among the total of 21 patients who were included in the final analyses, 17 were diagnosed with TIO, while four were proven to have other causes of HO. 68 Ga-DOTANOC PET/CT produced positive results in 16 of the 17 patients with TIO, representing a sensitivity of 94.1%. Moreover, the 68 Ga-DOTANOC PET/CT results were negative in 3 of the 4 patients without TIO, representing a specificity of 75.0%. The overall accuracy of 68 Ga-DOTANOC PET/CT in locating the tumours responsible for TIO is 90.5%. In particular, 68 Ga-DOTANOC PET/CT detected the culprit tumours in 4 out of 10 patients with negative results on previous 18 F-FDG PET/CT and showed a significantly higher T/M ratio of tumours than 18 F-FDG PET/CT in the same patients ( n = 10; 4.76 ± 3.08 vs 1.95 ± 1.33, p < 0.05). Conclusions 68 Ga-DOTANOC PET/CT is an accurate imaging modality in the localisation of tumours for TIO. It is superior to 18 F-FDG PET/CT and may be useful in the differential diagnosis of HO. Key Points • TIO should be considered a possible cause for patients diagnosed with HO, which usually needs to be differentiated from other aetiologies. • 68 Ga-DOTANOC PET/CT is an accurate imaging modality in locating culprit tumours for TIO, superior to 18 F-FDG PET/CT.