PET/CT-guided radiofrequency and cryoablation: is tumor fluorine-18 fluorodeoxyglucose activity dissipated by thermal ablation?

PURPOSE: To determine if tumor fluorine-18 fluorodeoxyglucose ((18)F-FDG) activity is dissipated by radiofrequency (RF) ablation or cryoablation during tumor ablation guided by positron emission tomography/computed tomography (PET/CT).
MATERIALS AND METHODS: This prospective study enrolled 12 patients (9 women and 3 men, 39-65 years old), each with at least one (18)F-FDG-avid liver, perihepatic, or lung tumor. Six patients (experimental group) underwent percutaneous PET/CT-guided RF ablation (n = 3) or cryoablation (n = 3). Six patients (control group) underwent diagnostic PET/CT-guided percutaneous biopsy. At a mean time of 103.5 minutes after a single intravenous (18)F-FDG dose, preprocedure and postprocedure PET/CT scans, separated by a mean time interval of 83.4 minutes, were obtained in all patients. Target tumor maximum standardized uptake value (TSUVmax) and ratio (SUVratio) of TSUVmax to normal liver average standardized uptake value (LSUVavg) were measured on all scans. Percentage changes in TSUVmax and SUVratio from preprocedure to postprocedure scans were compared for both groups and analyzed using the Student t test (P < .05 considered statistically significant).
RESULTS: For all patients in both groups, TSUVmax and SUVratio increased from preprocedure to postprocedure PET/CT scans without statistically significant differences. The mean percentage increase in TSUVmax for the ablation group was 32.5% (range 8.2%-46.7%) and for the biopsy group was 24.6% (3.7%-42.4%; P = .45). The mean percentage increase in SUVratio for the ablation group was 47.9% (18.8%-69.6%) and for the biopsy group was 37.6% (9.4%-65%; P = .37).
CONCLUSIONS: Tumor (18)F-FDG activity is not dissipated by percutaneous RF ablation or cryoablation. When performing (18)F-FDG PET/CT-guided RF ablation or cryoablation, changes in target tumor (18)F-FDG activity cannot be used to monitor treatment effects.