title: Sequential PET/CT with [18F]-FDG Predicts Pathological Tumor Response to Preoperative Short Course Radiotherapy with Delayed Surgery in Patients with Locally Advanced Rectal Cancer Using Logistic Regression Analysis.
abstract: Previous studies indicate that FDG PET/CT may predict pathological response in patients undergoing neoadjuvant chemo-radiotherapy for locally advanced rectal cancer (LARC). Aim of the current study is evaluate if pathological response can be similarly predicted in LARC patients after short course radiation therapy alone.
  
  
  METHODS
  Thirty-three patients with cT2-3, N0-2, M0 rectal adenocarcinoma treated with hypo fractionated short course neoadjuvant RT (5x5 Gy) with delayed surgery (SCRTDS) were prospectively studied. All patients underwent 3 PET/CT studies at baseline, 10 days from RT end (early), and 53 days from RT end (delayed). Maximal standardized uptake value (SUVmax), mean standardized uptake value (SUVmean) and total lesion glycolysis (TLG) of the primary tumor were measured and recorded at each PET/CT study. We use logistic regression analysis to aggregate different measures of metabolic response to predict the pathological response in the course of SCRTDS.
  
  
  RESULTS
  We provide straightforward formulas to classify response and estimate the probability of being a major responder (TRG1-2) or a complete responder (TRG1) for each individual. The formulas are based on the level of TLG at the early PET and on the overall proportional reduction of TLG between baseline and delayed PET studies.
  
  
  CONCLUSIONS
  This study demonstrates that in the course of SCRTDS it is possible to estimate the probabilities of pathological tumor responses on the basis of PET/CT with FDG. Our formulas make it possible to assess the risks associated to LARC borne by a patient in the course of SCRTDS. These risk assessments can be balanced against other health risks associated with further treatments and can therefore be used to make informed therapy adjustments during SCRTDS.
authors.affiliation: Radiation Oncology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Biagio
authors.initials: B
authors.lastname: Pecori
authors.affiliation: Nuclear Medicine Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Secondo
authors.initials: S
authors.lastname: Lastoria
authors.affiliation: Nuclear Medicine Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Corradina
authors.initials: C
authors.lastname: Caracò
authors.affiliation: Department of Economics, Universidad Carlos III, Madrid, Spain.
authors.forename: Marco
authors.initials: M
authors.lastname: Celentani
authors.affiliation: Pathology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Tatangelo
authors.affiliation: Gastrointestinal Medical Oncology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Avallone
authors.affiliation: Gastrointestinal Surgery Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Rega
authors.affiliation: Radiation Oncology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Giampaolo
authors.initials: G
authors.lastname: De Palma
authors.affiliation: Medical Physics Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Mormile
authors.affiliation: Experimental Pharmacology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Budillon
authors.affiliation: Radiation Oncology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Muto
authors.affiliation: Gastrointestinal Surgery Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bianco
authors.affiliation: Nuclear Medicine Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Aloj
authors.affiliation: Diagnostic Radiology Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Petrillo
authors.affiliation: Gastrointestinal Surgery Unit, Istituto Nazionale Tumori "Fondazione G. Pascale" IRCCS, Napoli, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Delrio
mesh_terms: D000368:Aged; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods; D011300:Preoperative Care; D011379:Prognosis; D012372:ROC Curve; D011878:Radiotherapy / Q000379:methods; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000532:radiotherapy / Q000601:surgery; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18