title: Evaluation of ¹⁸F-FDG-PET for early detection of suboptimal response of rectal cancer to preoperative chemoradiotherapy: a prospective analysis.
abstract: BACKGROUND
  Early identification of inadequate response to preoperative chemoradiotherapy (CRT) may spare rectal cancer patients the toxicity of ineffective treatment. We prospectively evaluated tumor response with (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) early in the course of preoperative CRT.
  
  
  METHODS
  A total of 27 prospectively accrued patients with locally advanced rectal cancer (T(3-4)/N(1)) received preoperative CRT (5040 cGy + 5FU-based chemotherapy). Patients underwent PET scanning before and 8-14 days after commencement of CRT. Scans were interpreted using 3 standard parameters: SUV(max), SUV(avg), and total lesion glycolysis (TLG) as well as an investigational parameter: visual response score (VRS). Percent pathologic response was quantified as a continuous variable. All PET parameters were correlated with pathology. Pathologic complete/near-complete response was defined as ≥95% tumor destruction, suboptimal response as <95%. Statistical analysis was performed using the Wilcoxon rank sum test and receiver operating characteristic (ROC) curve analysis.
  
  
  RESULTS
  Of the 27 patients, 11 (41%) had pathologic complete/near-complete response; 16 (59%) had suboptimal response. SUV(max), SUV(avg), and TLG did not discriminate between responders and nonresponders. Visual response score (VRS) was statistically significantly higher for complete/near-complete responders than for suboptimal responders (65 vs. 33%, P = 0.02). Suboptimal responders were identified with 94% sensitivity and 78% accuracy using a VRS cut-off of 50%.
  
  
  CONCLUSIONS
  In this pilot study, FDG-PET at 8-14 days after the beginning of preoperative CRT was unsuccessful at predicting pathological response with enough accuracy to justify an early change in therapy.
authors.affiliation: Department of Surgery (Colorectal Service), Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Leibold
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Akhurst
authors.forename: David B
authors.initials: DB
authors.lastname: Chessin
authors.forename: Henry W
authors.initials: HW
authors.lastname: Yeung
authors.forename: Homer
authors.initials: H
authors.lastname: Macapinlac
authors.forename: Jinru
authors.initials: J
authors.lastname: Shia
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Minsky
authors.forename: Leonard B
authors.initials: LB
authors.lastname: Saltz
authors.forename: Elyn
authors.initials: E
authors.lastname: Riedel
authors.forename: Madhu
authors.initials: M
authors.lastname: Mazumdar
authors.forename: Philip B
authors.initials: PB
authors.lastname: Paty
authors.forename: Martin R
authors.initials: MR
authors.lastname: Weiser
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Wong
authors.forename: Steven M
authors.initials: SM
authors.lastname: Larson
authors.forename: José G
authors.initials: JG
authors.lastname: Guillem
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000556:secondary / Q000628:therapy*; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D059248:Chemoradiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D005472:Fluorouracil / Q000008:administration & dosage; D005500:Follow-Up Studies; D006801:Humans; D002955:Leucovorin / Q000008:administration & dosage; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging / Q000628:therapy; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D011300:Preoperative Care; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*; D012680:Sensitivity and Specificity; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D002955:Leucovorin; D005472:Fluorouracil