Dual-Tracer PET/CT in Renal Angiomyolipoma and Subtypes of Renal Cell Carcinoma

We studied the metabolic characteristics of RCC subtypes and angiomyolipoma with F-18-FDG and C-11-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 C-11-acetate/F-18-FDG PET and attenuation density on CT. Receiver operating characteristic (ROC) curve was analyzed to define the threshold of C-11-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 F-18-FDG but markedly increased C-11-acetate metabolism, significantly higher than RCC (C-11-acetate SUVmax ratio = 4.11 +/- 0.53 vs 2.00 +/- 0.71; P < 0.05). C-11-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 C-11-acetate but not F-18-FDG, whereas papillary RCC were primarily the opposite. RCC-CC showed variable dual-tracer uptake: high-grade more avid for F-18-FDG, low-grade more for C-11-acetate. Four RCC cases negative by dual-tracers were of low- grade RCC-CC. "Primary RCC being F-18-FDG-avid" was the only independent predictor of RCC recurrence in 3 years (P G 0.05), with a median disease-free survival of 22 months. Conclusion: C-11-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.