250wordObjective: This study aimed to validate an MRI staging classification that preoperatively assessed the relationship between tumour and the low rectal cancer surgical resection plane (mrLRP). Results: Overall pCRM involvement was 9·0% ( 95% CI 5·9-12·3%); significantly lower than previously reported rates of 30%. Patients with no adverse MRI features and a L'P -preserving surgery without preoperative radiotherapy, resulting in a 1.6% pCRM rate. The pCRM rate increased five-fold for Background Conclusions:The study validated MRI low rectal plane assessment; reducing pCRM involvement and avoiding overtreatment through selective pre-operative therapy and rationalised use of permanent colostomy. It also highlights the importance of post-treatment re-staging.