title: Early prediction of histopathological response of rectal tumors after one week of preoperative radiochemotherapy using 18 F-FDG PET-CT imaging. A prospective clinical study.
abstract: BACKGROUND
  Preoperative radiochemotherapy (RCT) is standard in locally advanced rectal cancer (LARC). Initial data suggest that the tumor's metabolic response, i.e. reduction of its 18 F-FDG uptake compared with the baseline, observed after two weeks of RCT, may correlate with histopathological response. This prospective study evaluated the ability of a very early metabolic response, seen after only one week of RCT, to predict the histopathological response to treatment.
  
  
  METHODS
  Twenty patients with LARC who received standard RCT regimen followed by radical surgery participated in this study. Maximum standardized uptake value (SUV-MAX), measured by PET-CT imaging at baseline and on day 8 of RCT, and the changes in FDG uptake (ΔSUV-MAX), were compared with the histopathological response at surgery. Response was classified by tumor regression grade (TRG) and by achievement of pathological complete response (pCR).
  
  
  RESULTS
  Absolute SUV-MAX values at both time points did not correlate with histopathological response. However, patients with pCR had a larger drop in SUV-MAX after one week of RCT (median: -35.31% vs -18.42%, p = 0.046). In contrast, TRG did not correlate with ΔSUV-MAX. The changes in FGD-uptake predicted accurately the achievement of pCR: only patients with a decrease of more than 32% in SUV-MAX had pCR while none of those whose tumors did not show any decrease in SUV-MAX had pCR.
  
  
  CONCLUSIONS
  A decrease in ΔSUV-MAX after only one week of RCT for LARC may be able to predict the achievement of pCR in the post-RCT surgical specimen. Validation in a larger independent cohort is planned.
authors.affiliation: Institute of Oncology, Beilinson Hospital, Petah Tiqva, Israel.
authors.forename: Natalia
authors.initials: N
authors.lastname: Goldberg
authors.forename: Yulia
authors.initials: Y
authors.lastname: Kundel
authors.forename: Ofer
authors.initials: O
authors.lastname: Purim
authors.forename: Hanna
authors.initials: H
authors.lastname: Bernstine
authors.forename: Noa
authors.initials: N
authors.lastname: Gordon
authors.forename: Sara
authors.initials: S
authors.lastname: Morgenstern
authors.forename: Efraim
authors.initials: E
authors.lastname: Idelevich
authors.forename: Nir
authors.initials: N
authors.lastname: Wasserberg
authors.forename: Aaron
authors.initials: A
authors.lastname: Sulkes
authors.forename: David
authors.initials: D
authors.lastname: Groshar
authors.forename: Baruch
authors.initials: B
authors.lastname: Brenner
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000627:therapeutic use*; D000069287:Capecitabine; D059248:Chemoradiotherapy; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D005260:Female; D019788:Fluorodeoxyglucose F18; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D011300:Preoperative Care; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D005641:Tegafur / Q000008:administration & dosage; D014057:Tomography, X-Ray Computed; D014498:Uracil / Q000008:administration & dosage
chemical_list: D019275:Radiopharmaceuticals; D003841:Deoxycytidine; D019788:Fluorodeoxyglucose F18; D005641:Tegafur; D014498:Uracil; D000069287:Capecitabine; D005472:Fluorouracil