Perfusion MRI for the prediction of treatment response after preoperative chemoradiotherapy in locally advanced rectal cancer

Objectives To evaluate the utility of perfusion MRI as a potential biomarker for predicting response to chemoradiotherapy (CRT) in locally advanced rectal cancer. Methods Thirty-nine patients with primary rectal carcinoma who were scheduled for preoperative CRT were prospectively recruited. Perfusion MRI was performed with a 3.0-T MRI system in all patients before therapy, at the end of the 2nd week of therapy, and before surgery. The K trans (volume transfer constant) and V e (extracellular extravascular space fraction) were calculated. Results Before CRT, the mean tumour K trans in the downstaged group was significantly higher than that in the non-downstaged group ( P = 0.0178), but there was no significant difference between tumour regression grade (TRG) responders and TRG non-responders ( P = 0.1392). Repeated-measures analysis of variance (ANOVA) showed significant differences for evolution of K trans values both between downstaged and non-downstaged groups ( P = 0.0215) and between TRG responders and TRG non-responders ( P = 0.0001). Regarding V e , no significant differences were observed both between downstaged and non-downstaged groups ( P = 0.689) or between TRG responders and TRG non-responders ( P = 0.887). Conclusion Perfusion MRI of rectal cancer can be useful for assessing tumoural K trans changes by CRT. Tumours with high pre-CRT K trans values tended to respond favourably to CRT, particularly in terms of downstaging criteria. Key Points • Perfusion MRI can now assess therapeutic response of tumours to therapy . • Tumours with high initial K trans values responded favourably to chemoradiotherapy . • Perfusion MRI of rectal cancer may help with decisions about management .