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

Radiat Oncol. 2012 Aug 1;7:124. doi: 10.1186/1748-717X-7-124.


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.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Antineoplastic Combined Chemotherapy Protocols / administration & dosage
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Capecitabine
  • Chemoradiotherapy*
  • Deoxycytidine / administration & dosage
  • Deoxycytidine / analogs & derivatives
  • Female
  • Fluorodeoxyglucose F18*
  • Fluorouracil / administration & dosage
  • Fluorouracil / analogs & derivatives
  • Humans
  • Image Processing, Computer-Assisted
  • Male
  • Middle Aged
  • Multimodal Imaging
  • Neoplasm Staging
  • Positron-Emission Tomography
  • Preoperative Care
  • Prognosis
  • Prospective Studies
  • Radiopharmaceuticals*
  • Radiotherapy Dosage
  • Rectal Neoplasms / diagnostic imaging
  • Rectal Neoplasms / pathology
  • Rectal Neoplasms / therapy*
  • Tegafur / administration & dosage
  • Tomography, X-Ray Computed
  • Uracil / administration & dosage


  • Radiopharmaceuticals
  • Deoxycytidine
  • Fluorodeoxyglucose F18
  • Tegafur
  • Uracil
  • Capecitabine
  • Fluorouracil

Supplementary concepts

  • 1-UFT protocol