68ga-dotanoc and Carcinoma--Medullary

To prospectively evaluate the role of Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI-octreotide (Ga-DOTA-NOC) PET-CT in patients with recurrent medullary thyroid carcinoma (MTC) and compare the same with F-fluorodeoxyglucose (F-FDG) PET-CT.. Fifty-two consecutive patients with recurrent MTC based on raised serum calcitonin levels underwent Ga-DOTA-NOC PET-CT. In addition, 41 patients also underwent F-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.. Overall, Ga-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), Ga-DOTA-NOC PET-CT proved superior to F-FDG PET-CT with a higher sensitivity (75.61 vs. 63.4%). However, the difference was statistically not significant (P=0.179). Ga-DOTA-NOC PET-CT was superior to F-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 Ga-DOTA-NOC or F-FDG PET-CT.. Both Ga-DOTA-NOC PET-CT and F-FDG PET-CT are able to localize disease recurrence in patients with MTC, and their role appears to be complementary for this purpose.

Topics: Adult; Aged; Carcinoma, Medullary; Female; Fluorodeoxyglucose F18; Humans; Lymph Nodes; Male; Middle Aged; Multimodal Imaging; Neck; Neoplasm Recurrence, Local; Organometallic Compounds; Positron-Emission Tomography; Prospective Studies; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity; Thyroid Neoplasms; Tomography, X-Ray Computed

In this technical note, an unusual discordance between diagnostic and posttherapeutic scan resulting from the use of different somatostatin receptor ligands in two settings is described. Such observation, we believe, is multifactorial, but most importantly arises due to different receptor affinity profile of the ligands and different somatostatin receptor subtype expression in different tumors. It is important for the treating physician to be aware of this phenomenon that would aid in improving our understanding of complex ligand-receptor interactions in various somatostatin receptor-positive tumors with its possible implications for therapeutic decision making with radiolabeled somatostatin receptor analogues.

Topics: Artifacts; Carcinoma, Medullary; Humans; Isotope Labeling; Male; Middle Aged; Neoplasm Metastasis; Octreotide; Organometallic Compounds; Positron-Emission Tomography; Radiation Dosage; Radiotherapy Dosage; Receptors, Somatostatin; Somatostatin; Tomography, X-Ray Computed