Abstract
OBJECTIVES: To examine whether post-chemoradiotherapy (CRT) DCE-MRI can identify rectal cancer patients with pathologic complete response (pCR). METHODS: 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. RESULTS: 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. CONCLUSION: K (trans) could be used to identify patients with 90 % or more response to chemoradiotherapy for rectal cancer with an AUC of 0.7. KEY POINTS: • 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.