Abstract
1925
Objectives To compare 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) PET/CT studies performed in the same patients for discriminating between benign and malignant adrenal tumors.
Methods Twenty three patients with 23 adrenal tumors (size range: 15-85 mm and solid part CT density range: 13-53 HU) underwent both FDG and FLT PET/CT studies. On visual assessment, the tracer uptake in a tumor was positive and negative when it exceeded and did not exceed that of surrounding normal tissue, respectively. The tracer uptake was also quantified by calculating maximum standardized uptake value (SUVmax). The difference in each tracer SUVmax between benign and malignant tumors was examined using the Mann-Whitney’s U test. Differences in diagnostic indexes for diagnosing malignancy between both tracer PET/CT studies were estimated using the McNemar exact test.
Results There were 19 benign (15 lipid-poor adenomas, 2 myelolipomas, 1 schwannoma and 1 pheochromocytoma) and 4 malignant (3 metastases and 1 lymphoma) tumors. FDG uptake was positive for 13 of 19 benign tumors and for all malignant tumors. The sensitivity, specificity and accuracy for diagnosing malignancy were 100% (4/4), 31.6% (6/19) and 43.5% (10/23), respectively on FDG PET/CT. There was no significant difference in FDG SUVmax between malignant and benign tumors (5.0 ± 4.6 vs. 3.1 ± 1.9, P=0.19). FLT uptake was negative for 18 of 19 benign tumors and positive for all malignant tumors. The sensitivity, specificity and accuracy for diagnosing malignancy were 100% (4/4), 94.7% (18/19) and 95.7% (22/23), respectively on FLT PET/CT. There was a significant difference in FLT SUVmax between malignant and benign tumors (3.8 ± 1.8 vs. 1.9 ± 0.8, P=0.005). FLT PET/CT was superior to FDG PET/CT in the specificity (P=0.002) and accuracy (P=0.002), respectively.
Conclusions FLT PET/CT might be useful for discriminating between benign and malignant adrenal tumors.