title: PET-CT after radiofrequency ablation of colorectal liver metastases: suggestions for timing and image interpretation.
abstract: BACKGROUND
  The main area of concern regarding radiofrequency ablation (RFA) of colorectal liver metastases is the risk of developing a local site recurrence (LSR). Reported accuracy of PET-CT in detecting LSR is high compared to morphological imaging alone, but no internationally accepted criteria for image interpretation have been defined. Our aim was to assess criteria for FDG PET-CT image interpretation following 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, with FDG-PET follow-up within one year after treatment were included. Results of repeat FDG-PET scans were evaluated until a LSR was diagnosed. Results. One hundred-seventy scans were obtained for 79 patients (179 lesions), 57 scans (72%) were obtained within 6 months of treatment. Thirty patients developed local recurrence; 29 (97%) within 1 year. Only 2% of lesions of <1cm and 4% of <2 cm showed a LSR.
  
  
  CONCLUSIONS
  The majority of local site recurrences are diagnosed within one year after RFA. Regular follow-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-up of lesions <2 cm may be limited.
authors.affiliation: Department of Surgery, VU University Medical Centre, Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands. Electronic address: k.nielsen@vumc.nl.
authors.forename: Karin
authors.initials: K
authors.lastname: Nielsen
authors.forename: Aukje A J M
authors.initials: AA
authors.lastname: van Tilborg
authors.forename: Hester J
authors.initials: HJ
authors.lastname: Scheffer
authors.forename: Martijn R
authors.initials: MR
authors.lastname: Meijerink
authors.forename: Elly S M
authors.initials: ES
authors.lastname: de Lange-de Klerk
authors.forename: Sybren
authors.initials: S
authors.lastname: Meijer
authors.forename: Emile F I
authors.initials: EF
authors.lastname: Comans
authors.forename: M Petrousjka
authors.initials: MP
authors.lastname: van den Tol
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017115:Catheter Ablation / Q000401:mortality; D002648:Child; D002675:Child, Preschool; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000175:diagnosis / Q000556:secondary* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000706:statistics & numerical data; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000517:prevention & control*; D009426:Netherlands; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult
keywords: FDG-PET; Liver Neoplasms/surgery; Liver neoplasms/secondary; Local; Neoplasm recurrence; Radiofrequency ablation