Prospective evaluation of 68Ga-DOTA-NOC PET-CT in patients with recurrent medullary thyroid carcinoma

Abstract

Objective To prospectively evaluate the role of 68Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI3-octreotide (68Ga-DOTA-NOC) PET-CT in patients with recurrent medullary thyroid carcinoma (MTC) and compare the same with 18F-fluorodeoxyglucose (18F-FDG) PET-CT. Materials and methods Fifty-two consecutive patients with recurrent MTC based on raised serum calcitonin levels underwent 68Ga-DOTA-NOC PET-CT. In addition, 41 patients also underwent 18F-FDG PET-CT. PET-CT images were evaluated by two experienced nuclear medicine physicians both qualitatively and quantitatively (standardized uptake value). Histopathology (when available), correlation with conventional imaging modalities (ultrasonography/CT/MRI) and subsequent clinical/imaging follow-up were used as reference standard. Serum calcitonin levels were correlated with findings of PET-CT. Results Overall, 68Ga-DOTA-NOC PET-CT showed a sensitivity of 80.7% [95% confidence interval (CI) 67.4–90.3] and a positive predictive value of 100% (95% CI 91.5–100) for detecting recurrent MTC. When both were available (n=41), 68Ga-DOTA-NOC PET-CT proved superior to 18F-FDG PET-CT with a higher sensitivity (75.61 vs. 63.4%). However, the difference was statistically not significant (P=0.179). 68Ga-DOTA-NOC PET-CT was superior to 18F-FDG PET-CT for detecting recurrence in cervical lymph nodes (P<0.001). Both modalities were concordant in 75% of cases. No significant cut-off level of calcitonin could be derived for either 68Ga-DOTA-NOC or 18F-FDG PET-CT. Conclusion Both 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT are able to localize disease recurrence in patients with MTC, and their role appears to be complementary for this purpose.