title: Neither FDG-PET Nor CT can distinguish between a pathological complete response and an incomplete response after neoadjuvant chemoradiation in locally advanced rectal cancer: a prospective study.
abstract: OBJECTIVE
  To prospectively compare the ability of flourodeoxyglucose-positron emission tomography (FDG-PET) and computed tomography (CT) to identify a pathological complete response (pCR) in patients with rectal cancer treated by chemoradiation.
  
  
  BACKGROUND
  A major obstacle in pursuing nonoperative management in patients with rectal cancer after chemoradiation is the inability to identify a pCR preoperatively.
  
  
  METHODS
  A total of 121 patients with rectal cancer were prospectively enrolled. FDG-PET scans and helical CT scans were obtained before and after neoadjuvant chemoradiation. Consensus readings of PET and CT scans were used to classify certainty of disease (5-point confidence rating scale). The ability of PET and CT scans to accurately distinguish a pCR (ypT0) from an incomplete response (ypT1-4) was estimated using the area under the receiver operating characteristic curve (AUC).
  
  
  RESULTS
  Of the 121 patients, 26 (21%) had a pCR. PET and CT scans were equally inadequate at distinguishing a pCR from an incomplete response (AUC = 0.64 for both, P = 0.97). Among the 26 patients with a pCR, 14 (54%) and 5 (19%) were classified as complete responders on PET and CT scans, respectively. Among the 95 patients with an incomplete pathological response, 63 (66%) and 90 (95%) were classified as incomplete responders on PET and CT scans, respectively. None of the individual PET parameters, including visual response score, mean standard uptake value (SUVmean), maximum SUV (SUVmax), and total lesion glycolysis, accurately distinguished a pCR (AUCs = 0.57-0.73).
  
  
  CONCLUSIONS
  Neither PET nor CT scans have adequate predictive value to be clinically useful in distinguishing a pCR from an incomplete response and, therefore, should not be obtained for the purpose of attempting to predict a pCR after neoadjuvant chemoradiation for rectal cancer.
authors.affiliation: Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. guillemj@mskcc.org
authors.forename: José G
authors.initials: JG
authors.lastname: Guillem
authors.forename: Jeannine A
authors.initials: JA
authors.lastname: Ruby
authors.forename: Tobias
authors.initials: T
authors.lastname: Leibold
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Akhurst
authors.forename: Henry W
authors.initials: HW
authors.lastname: Yeung
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Gollub
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Ginsberg
authors.forename: Jinru
authors.initials: J
authors.lastname: Shia
authors.forename: Arief A
authors.initials: AA
authors.lastname: Suriawinata
authors.forename: Elyn R
authors.initials: ER
authors.lastname: Riedel
authors.forename: Madhu
authors.initials: M
authors.lastname: Mazumdar
authors.forename: Leonard B
authors.initials: LB
authors.lastname: Saltz
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Minsky
authors.forename: Garrett M
authors.initials: GM
authors.lastname: Nash
authors.forename: Philip B
authors.initials: PB
authors.lastname: Paty
authors.forename: Larissa K
authors.initials: LK
authors.lastname: Temple
authors.forename: Martin R
authors.initials: MR
authors.lastname: Weiser
authors.forename: Steven M
authors.initials: SM
authors.lastname: Larson
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059186:Chemoradiotherapy, Adjuvant; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D012372:ROC Curve; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D012007:Rectum / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D036542:Tomography, Spiral Computed; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18