title: Dual-tracer PET/CT in renal angiomyolipoma and subtypes of renal cell carcinoma.
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 C-acetate but not 18F-FDG, whereas papillary RCC were primarily the opposite. RCC-CC showed variable dual-tracer uptake: high-grade more avid for F-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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Nuclear Medicine and PET, Hong Kong Sanatorium and Hospital, Hong Kong, China. garrettho@hksh.com
authors.forename: Chi-Lai
authors.initials: CL
authors.lastname: Ho
authors.forename: Sirong
authors.initials: S
authors.lastname: Chen
authors.forename: Kossen Man Tzit
authors.initials: KM
authors.lastname: Ho
authors.forename: Wai Kong
authors.initials: WK
authors.lastname: Chan
authors.forename: Yim Lung
authors.initials: YL
authors.lastname: Leung
authors.forename: Kam Chau
authors.initials: KC
authors.lastname: Cheng
authors.forename: Ka-Nin
authors.initials: KN
authors.lastname: Wong
authors.forename: Man-ki
authors.initials: MK
authors.lastname: Cheung
authors.forename: Kwok Kee
authors.initials: KK
authors.lastname: Wong
mesh_terms: D000328:Adult; D018207:Angiomyolipoma / Q000000981:diagnostic imaging*; D002292:Carcinoma, Renal Cell / Q000145:classification / Q000000981:diagnostic imaging*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011379:Prognosis; D014057:Tomography, X-Ray Computed