Clinical Nuclear Medicine
Original Articles
Ho, Chi-lai MD*; Chen, Sirong PhD*†; Ho, Kossen Man Tzit MBBCh, PhD‡; Chan, Wai Kong MBBCh§; Leung, Yim Lung MBBS*; Cheng, Kam Chau MBBS*; Wong, Ka-nin MBBS*; Cheung, Man-ki PhD*; Wong, Kwok Kee MBBS‡
From the *Department of Nuclear Medicine and PET, and †Medical Physics and Research Department, Hong Kong Sanatorium and Hospital; ‡Hong Kong Urology Clinic; and §Department of Pathology, Hong Kong Sanatorium and Hospital, Hong Kong, China.
Received for publication April 18, 2012; and revision accepted June 6, 2012.
Conflicts of interest and sources of funding: none declared.
Reprints: Chi-lai Ho, MD, Department of Nuclear Medicine and PET Hong Kong Sanatorium and Hospital, 2 Village Road, Happy Valley, Hong Kong, China. E-mail: [email protected].
Abstract
We studied the metabolic characteristics of RCC subtypes and angiomyolipoma with 18F-FDG and 11C-acetate PET/CT.
Methods
Fifty-eight patients with both baseline CT and dual-tracer PET/CT were recruited: 10 angiomyolipoma (16 lesions) and 48 RCC (50 lesions). Each lesion was assessed for SUVmax ratio (lesion-to-normal kidney) on 11C-acetate/18F-FDG PET and attenuation density on CT. Receiver operating characteristic (ROC) curve was analyzed to define the threshold of 11C-acetate SUVmax ratio for differentiating angiomyolipoma from RCC. Thirty-nine RCC patients were selected for 3-year disease-free survival analysis.
Results
All angiomyolipoma showed negative 18F-FDG but markedly increased 11C-acetate metabolism, significantly higher than RCC (11C-acetate SUVmax ratio = 4.11 ± 0.53 vs 2.00 ± 0.71; P < 0.05). 11C-acetate SUVmax ratio = 3.71 could differentiate angiomyolipoma including “fat-poor angiomyolipoma” (n = 10) from RCC with sensitivity of 93.8% (15/16) and specificity of 98.0% (49/50). Different RCC subtypes/grades (25 low- and 11 high-grade clear cell [CC], 7 chromophobe, 4 papillary, and 1 collecting duct) were found to have different dual-tracer metabolic pattern (P < 0.05), with overall RCC detection sensitivity of 90% (45/50). All chromophobe RCC were avid only for 11C-acetate but not 18F-FDG, whereas papillary RCC were primarily the opposite. RCC-CC showed variable dual-tracer uptake: high-grade more avid for 18F-FDG, low-grade more for 11C-acetate. Four RCC cases negative by dual-tracers were of low-grade RCC-CC. “Primary RCC being 18F-FDG-avid” was the only independent predictor of RCC recurrence in 3 years (P < 0.05), with a median disease-free survival of 22 months.
Conclusion
11C-acetate PET/CT helps in differentiating “fat-poor angiomyolipoma” from RCC. Dual-tracer PET/CT has value in diagnosis of RCC subtypes and predicting survival.