title: Differentiation between peri-anastomotic inflammatory changes and local recurrence following neoadjuvant radiochemotherapy surgery for colorectal cancer using visual and semiquantitative analysis of PET-CT data.
abstract: OBJECTIVE
  The aim of this study was to evaluate the usefulness of visual and semiquantitative [¹⁸F]fluorodeoxy-glucose (FDG) positron emission tomography-computed tomography (PET-CT) data for the diagnosis of peri-anastomotic colorectal cancer recurrence, taking into account the time period between surgery and [¹⁸F]FDG PET-CT scanning.
  
  
  METHODS
  The study population consisted of 70 patients who had prior preoperative radiochemotherapy and surgical resection of the primary tumor and who underwent whole body [¹⁸F]FDG PET-CT scanning for the detection of recurrent disease. Visual and semiquantitative (SUV(max)) analysis of [¹⁸F]FDG uptake at the peri-anastomosis was performed. The final diagnosis was based on pathological proof or clinical and/or imaging follow-up data.
  
  
  RESULTS
  On visual reading, 27 patients exhibited increased [¹⁸F]FDG uptake at the peri-anastomosis. Of these, 11 (41%) patients had a local tumor recurrence and 16 (59%) had no recurrent tumor. Among the 43 patients without increased [¹⁸F]FDG uptake at the peri-anastomosis, none had local tumor recurrence. On semiquantitation, SUV(max) in patients with and without a local recurrence overlapped. However, when the time period between surgery and [¹⁸F]FDG PET-CT scanning was taken into account, overlap of SUV(max) was mainly observed within a postoperative period of ≤12 months; thereafter, a threshold SUV(max) of 3.2 discriminated between benign and malignant lesions in all but one patient.
  
  
  CONCLUSIONS
  In our series, visually increased [¹⁸F]FDG uptake at the peri-anastomosis was 100% sensitive but non-specific (73% specificity) for the diagnosis of local tumor recurrence. On the other hand, normal [¹⁸F]FDG uptake at the peri-anastomosis precluded a local tumor recurrence (a negative predictive value of 100%). In addition, semiquantitative (SUV(max)) analysis of [¹⁸F]FDG uptake at the peri-anastomosis may increase specificity (up to 97%), while preserving maximum sensitivity, if the postoperative period is >12 months.
authors.affiliation: Department of Radiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Smeets
authors.forename: H
authors.initials: H
authors.lastname: Ham
authors.forename: W
authors.initials: W
authors.lastname: Ceelen
authors.forename: T
authors.initials: T
authors.lastname: Boterberg
authors.forename: K
authors.initials: K
authors.lastname: Verstraete
authors.forename: I
authors.initials: I
authors.lastname: Goethals
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy; D003937:Diagnosis, Differential; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18