title: Comparison of (18)F-FDG PET/CT methods of analysis for predicting response to neoadjuvant chemoradiation therapy in patients with locally advanced low rectal cancer.
abstract: OBJECTIVE
  The aim of this study was to prospectively investigate the predictive value of (18)F-FDG PET/CT semiquantitative parameters for locally advanced low rectal cancer (LARC) treated by neoadjuvant chemoradiation therapy (nCRT).
  
  
  METHODS
  68 patients with LARC had (18)F-FDG PET/CT scans twice (baseline and 5-6 weeks post-nCRT). All patients underwent surgery with preservation of the sphincter 8 weeks later. (18)F-FDG PET/CT analysis was performed by visual response assessment (VRA) and semiquantitative parameters: SUVmax(baseline), SUVmean(baseline), MTV(baseline), TLG(baseline), SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), TLG(post-nCRT); ΔSUVmax and mean and Response indexes (RImax% and RImean%). Assessment of nCRT tumor response was performed according to the Mandard's Tumor Regression Grade (TRG) and (y)pTNM staging on the surgical specimens. Concordances of VRA with TRG, and with (y)pTNM criteria were evaluated by Cohen's K. Results were compared by t student test for unpaired groups. ROC curve analysis was performed.
  
  
  RESULTS
  VRA analysis of post-nCRT (18)F-FDG PET/CT scan for the (y)pTNM outcome showed sensitivity, specificity, accuracy, PPV, and NPV of 87.5%, 66.7%, 83.8%, 92.5%, and 53.3%, respectively. Concordances of VRA with TRG and with (y)pTNM were moderate. For the outcome variable TRG, the statistical difference between responders and non-responders was significant for SUVmax(post-nCRT) and RImean%; for the outcome variable (y)pTNM, there was a significant difference for MTV(baseline), SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), RImax%, and RImean%. ROC analysis showed better AUCs: for the outcome variable TRG for SUVmax(post-nCRT), SUVmean(post-nCRT), and RImean%; for the outcome variable (y)pTNM for MTVbaseline, SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), RImax%, and RImean%. No significant differences among parameters were found.
  
  
  CONCLUSIONS
  Qualitative and semiquantitative evaluations for (18)F-FDG PET/CT are the optimal approach; a valid parameter for response prediction has still to be established.
authors.affiliation: Nuclear Medicine Unit, D.I.M., University of Bari "Aldo Moro", Bari, Italy.
authors.forename: Corinna
authors.initials: C
authors.lastname: Altini
authors.forename: Artor
authors.initials: A
authors.lastname: Niccoli Asabella
authors.forename: Raffaele
authors.initials: R
authors.lastname: De Luca
authors.forename: Margherita
authors.initials: M
authors.lastname: Fanelli
authors.forename: Cosimo
authors.initials: C
authors.lastname: Caliandro
authors.forename: Natale
authors.initials: N
authors.lastname: Quartuccio
authors.forename: Domenico
authors.initials: D
authors.lastname: Rubini
authors.forename: Angelina
authors.initials: A
authors.lastname: Cistaro
authors.forename: Severino
authors.initials: S
authors.lastname: Montemurro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rubini
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18