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 CRTwere 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 Ktrans (volume transfer constant) and Ve (extracellular extravascular space fraction) were calculated. Results Before CRT, the mean tumour Ktrans in the downstaged group was significantly higher than that in the nondownstaged group (P00.0178), but there was no significant difference between tumour regression grade (TRG) responders and TRG non-responders (P00.1392). Repeatedmeasures analysis of variance (ANOVA) showed significant differences for evolution of Ktrans values both between downstaged and non-downstaged groups (P00.0215) and between TRG responders and TRG non-responders (P00.0001). Regarding Ve, no significant differences were observed both between downstaged and non-downstaged groups (P00.689) or between TRG responders and TRG non-responders (P00.887). Conclusion Perfusion MRI of rectal cancer can be useful for assessing tumoural Ktrans changes by CRT. Tumours with high pre-CRT Ktrans 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 Ktrans values responded favourably to chemoradiotherapy. ̇ Perfusion MRI of rectal cancer may help with decisions about management.