[18F] DOPA PET/CT for the evaluation of primary or recurrent medullary thyroid carcinoma: In relation to basal and stimulated calcitonin as well as carcinoembryonic antigen

622 Background: Basal calcitonin (bCT) and carcinoembryonic antigen (CEA) may be used as tumor markers for diagnosis and follow-up of MTC. Recently, [18F] DOPA PET has been reported to be useful for detecting primary or recurrent MTC. However, until now, no observation was reported about the possible relation between the stimulated CT (sCT) levels and the results of [18F] DOPA PET as well as the possible difference in the [18F] DOPA PET results between the female and male patients. The aim of this study is to evaluate the role of [18F] DOPA PET/CT for the imaging of primary or recurrent medullary thyroid carcinoma especially the possible correlation between CT levels (bCT and sCT) and tracer uptake of [18F] DOPA as well as a gender difference in the [18F] DOPA PET results. Methods: Eighty-nine[18F] DOPA PET/CT examinations were performed in 50 patients (26 female, 24 male patients, mean age 59 ± 14 years, range 24 to 84) with histologically verified primary or recurrent MTC. 5 patients had a hereditary MTC. Serum bCT and CEA were measured in all patients. Calcium stimulation test (CST) was performed in 42 of the 50 patients. SUVmax was calculated for each lesion. Correlation and cutoff values were determined with IBM SPSS Statistics 24 using Pearson’s correlation, Chi square test and ROC. Results: Positive [18F] DOPA PET/CT results were shown in 71 examinations with a sensitivity of 80%. 43 patients had positive [18F] DOPA PET/CT scans with a sensitivity of 86%. 22 male patients (92%) had positive findings in [18F] DOPA PET/CT, whereas only 21 female patients (80%) were positive in the [18F] DOPA PET/CT. However, we found no significant difference in sensitivity between female and male patients. All 5 patients (100%) with hereditary MTC had positive PET/CT scans. Correlation between bCT and SUVmax was significant (pl0,01). Correlation between sCT and SUVmax was also significant (pl0,01). 58 examinations with positive [18F] DOPA PET had bCT levels g 48pg/mL with a sensitivity of 82% and a specificity of 72%. [18F] DOPA PET was positive in 35 examniations with sCT levels g 1808 pg/mL with a sensitivity of 73% and a specificity of 64%. Cutoff value for CEA values g 4ng/L had a sensitivity of 82% and a specificity of 67%. Conclusion: Tracer-uptake of [18F] DOPA (SUVmax) correlates significantly with bCT as well as sCT. We observed higher sensitivity of [18F] DOPA PET/CT in male patients than in female patients, however no significant difference was shown. Higher sensitivity of [18F] DOPA PET/CT tends to be found in patients with hereditary MTC as compared to patients with sporadic MTC. [18F] DOPA PET/CT may be especially useful in patients with bCT levels g 48 pg/mL or sCT levels g 1808 pg/mL or CEA g 4ng/L.