If tumor is stradling the peritoneal reflection how do you decide whether to treat with neoadjuvant chemo/RT vs just surgery?

There are many definitions used to delineate the sigmoid colon from the rectum. The peritoneal reflection is only one of these, and it may not be the most clinically useful. The location of the peritoneal reflection varies with age and gender, and it typically extends more inferiorly on the anterior...

May not be relevant and consider MR.