ABSTRACT
PURPOSE: This was a retrospective study to detect and map the extent of disease in recurrent medullary thyroid carcinoma (MTC) using the novel PET somatostatin analogue (68)Ga-DOTATATE and conventional (18)F-FDG positron emission tomography/computed tomography (PET/CT). METHODS: Eighteen patients (13 men, 5 women, median age: 54 years) who had previously been operated on for MTC and presented with biochemical (raised calcitonin levels) and/or imaging evidence of recurrence underwent both (68)Ga-DOTATATE and (18)F-FDG PET/CT within a maximum interval of 4 weeks (median interval of 1 week). (68)Ga-DOTATATE- and (18)F-FDG-avid lesions were recorded per patient as well as per region in six distinct regions: (1) thyroid bed-local recurrence, (2) cervical lymph nodes, (3) mediastinum, (4) lungs, (5) liver and (6) bones. The (68)Ga-DOTATATE and (18)F-FDG PET/CT findings were classified as positive or negative on visual interpretation. These findings were further characterised as concordant or discordant, depending on whether there was agreement or discrepancy in imaging with the two radiotracers. A separate analysis of the unenhanced CT component of the examination was performed. Verification of the lesions was achieved by histopathological analysis, further imaging studies and clinical follow-up. RESULTS: (68)Ga-DOTATATE PET/CT imaging achieved disease detection in 13 of 18 and (18)F-FDG PET/CT in 14 of 18 patients. These results corresponded to per-patient sensitivities of 72.2% [95% confidence interval (CI): 46.4-89.3%] for (68)Ga-DOTATATE versus 77.8% (95% CI: 51.9-92.6%) for (18)F-FDG (non-significant difference). (18)F-FDG revealed a total of 28 metastatic MTC regions and (68)Ga-DOTATATE 23 regions. In ten patients a discordant tracer pattern of per-region and/or per-lesion distribution of recurrent disease was observed, while in four patients a concordant pattern was noted (no lesions were detected by either modality in the remaining four patients). CONCLUSION: Neither (18)F-FDG nor (68)Ga-DOTATATE PET/CT can fully map the extent of disease in patients with recurrent MTC, although (18)F-FDG PET/CT may identify more lesions. However, (68)Ga-DOTATATE PET/CT can be a useful complementary imaging tool and may identify patients suitable for consideration of targeted radionuclide somatostatin analogue therapy.
Subject(s)
Carcinoma, Medullary/diagnosis , Fluorodeoxyglucose F18 , Neoplasm Recurrence, Local/diagnosis , Organometallic Compounds , Positron-Emission Tomography/methods , Thyroid Neoplasms/diagnosis , Tomography, X-Ray Computed/methods , Adult , Aged , Female , Humans , Male , Middle Aged , Radiopharmaceuticals , Reproducibility of Results , Sensitivity and Specificity , Subtraction Technique , Thyroid Gland/diagnostic imagingABSTRACT
UNLABELLED: Our purpose was to compare the performance of (68)Ga-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1),Tyr(3)-octreotate (DOTATATE), a novel selective somatostatin receptor 2 PET ligand, and (18)F-FDG in the detection of pulmonary neuroendocrine tumors using PET/CT, with correlation of uptake and tumor grade on histology. METHODS: The imaging findings of the first 18 consecutive patients (8 men and 10 women) with pulmonary neuroendocrine tumors (11 typical carcinoids, 2 atypical carcinoids, 1 large cell neuroendocrine tumor, 1 small cell neuroendocrine carcinoma, 1 non-small cell lung cancer with neuroendocrine differentiation, and 2 cases of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia) who underwent (68)Ga-DOTATATE and (18)F-FDG PET/CT were reviewed. In all cases, the diagnosis was established on histology. RESULTS: Of 18 patients, 15 had primary tumors (median size, 2.7 cm; range, 0.5-8 cm) and 3 had recurrent tumors. All typical carcinoids showed high uptake of (68)Ga-DOTATATE (maximum standardized uptake value [SUV(max)] >or= 8.2), but 4 of 11 showed negative or minimal (18)F-FDG uptake (SUV(max) = 1.7-2.9). All tumors of higher grade showed high uptake of (18)F-FDG (SUV(max) >or= 11.7), but 3 of 5 showed only minimal accumulation of (68)Ga-DOTATATE (SUV(max) = 2.2-2.8). Neither case of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia showed uptake of (68)Ga-DOTATATE or (18)F-FDG. Typical carcinoids showed significantly higher uptake of (68)Ga-DOTATATE and significantly less uptake of (18)F-FDG than did tumors of higher grade (P = 0.002 and 0.005). There was no instance of false-positive uptake of (68)Ga-DOTATATE, but there were 3 sites of (18)F-FDG uptake secondary to inflammation. (68)Ga-DOTATATE was superior to (18)F-FDG in discriminating endobronchial tumor from distal collapsed lung (P = 0.02). CONCLUSION: Typical bronchial carcinoids showed higher and more selective uptake of (68)Ga-DOTATATE than of (18)F-FDG. Atypical carcinoids and higher grades had less (68)Ga-DOTATATE avidity but were (18)F-FDG-avid.
