PET-CT after radiofrequency ablation of colorectal liver metastases:Suggestions for timing and image interpretation

摘要

Introduction. The main area of concern regarding radiofrequency ablation (RFA) of colorectal liver metas-tases is the risk of developing a local site recurrence (LSR). Reported accuracy of PET-CT in detecting LSRis high compared to morphological imaging alone, but no internationally accepted criteria for imageinterpretation have been defined. Our aim was to assess criteria for FDG PET-CT image interpretationfollowing RFA, and to define a timetable for follow-up detection of LSR.Methods. Patients who underwent RFA for colorectal liver metastases between 2005 and 2011, withFDG-PET follow-up within one year after treatment were included. Results of repeat FDG-PET scans wereevaluated until a LSR was diagnosed.Results. One hundred-seventy scans were obtained for 79 patients (179 lesions), 57 scans (72%) wereobtained within 6 months of treatment. Thirty patients developed local recurrence; 29 (97%) within 1year. Only 2% of lesions of 〈1 cm and 4% of 〈2 cm showed a LSR.Conclusion. The majority of local site recurrences are diagnosed within one year after RFA. Regularfollow-up using FDG PET-CT within this period is advised, so repeated treatment can be initiated. Rim-shaped uptake may be present until 4?6 months, complicating evaluation. The benefit in the follow-upof lesions 〈2 cm may be limited.