title: The value of metabolic imaging to predict tumour response after chemoradiation in locally advanced rectal cancer.
abstract: BACKGROUND
  We aim to investigate the possibility of using 18F-positron emission tomography/computer tomography (PET-CT) to predict the histopathologic response in locally advanced rectal cancer (LARC) treated with preoperative chemoradiation (CRT).
  
  
  METHODS
  The study included 50 patients with LARC treated with preoperative CRT. All patients were evaluated by PET-CT before and after CRT, and results were compared to histopathologic response quantified by tumour regression grade (patients with TRG 1-2 being defined as responders and patients with grade 3-5 as non-responders). Furthermore, the predictive value of metabolic imaging for pathologic complete response (ypCR) was investigated.
  
  
  RESULTS
  Responders and non-responders showed statistically significant differences according to Mandard's criteria for maximum standardized uptake value (SUVmax) before and after CRT with a specificity of 76,6% and a positive predictive value of 66,7%. Furthermore, SUVmax values after CRT were able to differentiate patients with ypCR with a sensitivity of 63% and a specificity of 74,4% (positive predictive value 41,2% and negative predictive value 87,9%); This rather low sensitivity and specificity determined that PET-CT was only able to distinguish 7 cases of ypCR from a total of 11 patients.
  
  
  CONCLUSIONS
  We conclude that 18-F PET-CT performed five to seven weeks after the end of CRT can visualise functional tumour response in LARC. In contrast, metabolic imaging with 18-F PET-CT is not able to predict patients with ypCR accurately.
authors.affiliation: Division of Colon &Rectal Surgery - Department of Surgery, HUVN Granada, Spain. pablopalma@andaluciajunta.es
authors.forename: Pablo
authors.initials: P
authors.lastname: Palma
authors.forename: Raquel
authors.initials: R
authors.lastname: Conde-Muíño
authors.forename: Antonio
authors.initials: A
authors.lastname: Rodríguez-Fernández
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Segura-Jiménez
authors.forename: Rocío
authors.initials: R
authors.lastname: Sánchez-Sánchez
authors.forename: Javier
authors.initials: J
authors.lastname: Martín-Cano
authors.forename: Manuel
authors.initials: M
authors.lastname: Gómez-Río
authors.forename: José A
authors.initials: JA
authors.lastname: Ferrón
authors.forename: José M
authors.initials: JM
authors.lastname: Llamas-Elvira
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000378:metabolism / Q000532:radiotherapy; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011379:Prognosis; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000378:metabolism / Q000532:radiotherapy; D012680:Sensitivity and Specificity
chemical_list: D019788:Fluorodeoxyglucose F18