BACKGROUNDMorphologic imaging after radiofrequency ablation (RFA) of liver metastases is hampered by an inflammatory response in the ablation margin, making the identification of local tumor progression (LTP) difficult. The aim of this study was to evaluate the efficacy of early (18)F-FDG PET/CT scanning to monitor the effectiveness of RFA in colorectal liver metastases.

METHODSTwelve patients with 20 metastases were treated with RFA for colorectal liver metastases. They underwent PET/CT within 2 weeks before RFA and within 24 hours after RFA (so termed "early PET/CT"). PET/CT was repeated at 1, 3, and 6 months, and then every 6 months after ablation. The standard of reference was based on available clinical and radiological follow-up data.

RESULTSEarly PET/CT revealed total photopenia in 16 RFA-treated metastases, which were found to be without residual tumor on the final PET/CT scan. Three RFA-treated metastases with focal uptake were identified as local tumor progression, which necessitated further treatment. One RFA-treated metastasis with rim-shaped uptake was regarded as inflammation. The results of the early PET/CT scanning were consistent with the findings of the final follow-up.

CONCLUSIONSPET/CT performed within 24 hours after RFA can effectively detect whether residual tumor exists for colorectal cancer liver metastases. The results can guide further treatment, and may improve the efficacy of RFA.