Diffusion-Weighted Imaging for Rectal Cancer Response Monitoring After Neo-Adjuvant Radiochemotherapy: A Good Correlation with Pathological Response.

Martijn Intven¹, Onne Reerink¹, Taro Takahara², Marielle E. P. Philippens¹

Rectal cancer response analysis after neo-adjuvant radiochemotherepy (RCT) is important because good pathological response prediction enables safe omission of surgery in the group of clinical complete responders. Diffusion-weighted MR imaging (DWI) reflects the microanatomy in tissues and is frequently used in oncology for tissue characterisation and response assessment. In this study, we analysed rectal cancer response after neo-adjuvant RCT with DWI. Apparent diffusion coefficient (ADC) values were compared with the pathological rectal cancer regression grade. Unexpectedly, low post-RCT ADC values and low ADC differences correlated with a good pathological response after neo-adjuvant RCT.