Diagnostic efficiency of Ga-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 Ga-DOTANOC PET/CT in the localisation and diagnosis of TIO, and compared with F-FDG.

METHODS

Twenty-four consecutive patients with hypophosphataemic osteomalacia (HO) and suspicion of TIO who were referred to our centre for 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. Ga-DOTANOC PET/CT produced positive results in 16 of the 17 patients with TIO, representing a sensitivity of 94.1%. Moreover, the 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 Ga-DOTANOC PET/CT in locating the tumours responsible for TIO is 90.5%. In particular, Ga-DOTANOC PET/CT detected the culprit tumours in 4 out of 10 patients with negative results on previous F-FDG PET/CT and showed a significantly higher T/M ratio of tumours than F-FDG PET/CT in the same patients (n = 10; 4.76 ± 3.08 vs 1.95 ± 1.33, p < 0.05).

CONCLUSIONS

Ga-DOTANOC PET/CT is an accurate imaging modality in the localisation of tumours for TIO. It is superior to 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. • Ga-DOTANOC PET/CT is an accurate imaging modality in locating culprit tumours for TIO, superior to F-FDG PET/CT.