title: ¹⁸F-FDG PET/CT-based treatment response evaluation in locally advanced rectal cancer: a prospective validation of long-term outcomes.
abstract: OBJECTIVE
  To prospectively evaluate the usefulness of (18)F-FDG PET/CT) imaging for predicting histopathological response and long-term clinical outcomes in locally advanced rectal cancer (LARC).
  
  
  METHODS
  This prospective study included 38 patients with a confirmed diagnosis of LARC (cT3-4 or cN+) who underwent (18)F-FDG PET/CT before and after neoadjuvant therapy (NAT). Total mesorectal excision was scheduled 6 weeks after NAT and was followed by an expert histopathological analysis of the surgical specimen. Baseline variables and previously identified maximum FDG standardized uptake value (SUVmax) cut-off values before NAT (SUVmaxPRE ≥6) and after NAT (SUVmaxPOST ≥2), and the absolute and percentage reductions from baseline SUVmax (∆SUVmax <4 and ∆SUVmax% <65 %, respectively) were applied to differentiate patients showing a metabolic tumour response from nonresponders. These features were correlated with tumour regression grade (TRG), disease-free survival (DFS) and overall survival (OS).
  
  
  RESULTS
  Significantly higher 5-year DFS and OS were seen in 19 responders (TRG 3 or 4) than in 19 nonresponders (TRG 0-2; 94.4 vs. 48.8 %, p = 0.001; 94.7 vs. 63.2 %, p = 0.02, respectively). In multivariate analysis the only PET/CT SUVmax-based parameter significantly correlated with the likelihood of recurrence and survival was ∆SUV% <65 % (HR = 5.95, p = 0.02, for DFS; HR = 5.26, p = 0.04, for OS) CONCLUSION: This prospective study proved that (18)F-FDG PET/CT is a valuable imaging tool for assessing rectal cancer TRG and long-term prognosis, and could potentially serve as an intermediate endpoint in treatment optimization research and rectal cancer patient care.
authors: Department of Oncology, Hospital General Universitario Gregorio Marañón, Ave. Doctor Esquerdo 46, 28007 Madrid, Spain.
authors: Felipe A
authors: FA
authors: Calvo
authors: Claudio V
authors: CV
authors: Sole
authors: Dolores
authors: D
authors: de la Mata
authors: Luis
authors: L
authors: Cabezón
authors: Marina
authors: M
authors: Gómez-Espí
authors: Emilio
authors: E
authors: Alvarez
authors: Paz
authors: P
authors: Madariaga
authors: José L
authors: JL
authors: Carreras
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011379:Prognosis; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D015203:Reproducibility of Results; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18