Limited accuracy of DCE-MRI in identification of pathological complete responders after chemoradiotherapy treatment for rectal cancer.

Abstract

To examine whether post-chemoradiotherapy (CRT) DCE-MRI can identify rectal cancer patients with pathologic complete response (pCR). From a rectal cancer surgery database 2007-2014, 61 consecutive patients that met the following inclusion criteria were selected for analysis: (1) stage II/III primary rectal adenocarcinoma; (2) received CRT; (3) underwent surgery (4); underwent rectal DCE-MRI on a 1.5-T MRI scanner. Two experienced radiologists, in consensus, drew regions of interest (ROI) on the sagittal DCE-MRI image in the tumour bed. These were exported from ImageJ to in-house Matlab code for modelling using the Tofts model. K ^trans, K _ep and v _e values were compared to pathological response. Of the 61 initial patients, 37 had data considered adequate for fitting to obtain perfusion parameters. Among the 13 men and 24 women, median age 53 years, there were 8 pCR (22 %). K ^trans could not distinguish patients with pCR. For patients with 90 % or greater response, mean K ^trans and K _ep values were statistically significant (p = 0.032 and 0.027, respectively). Using a cutoff value of K ^trans = 0.25 min^-1, the AUC was 0.71. K ^trans could be used to identify patients with 90 % or more response to chemoradiotherapy for rectal cancer with an AUC of 0.7. • Chemoradiotherapy for rectal cancer causes decreased blood flow and permeability in the tumour bed. • Lower values of blood flow and permeability correlate with good tumour response. • K ^trans of 0.25min ^-1 best identifies patients with ≥90 % response with AUC 0.71.