MDT stage migration in MRI of significant rectal polyps and early rectal cancers

To audit the diagnostic accuracy of MRI for staging early and polyp rectal cancers with the purpose of identifying scope for service improvement.

This is an IRB approved retrospective study of patients who underwent staging MRI for rectal growths followed by upfront TME type surgery or local excision without neoadjuvant therapy between 2018 and 2021. MR-T-stage was compared with surgical histopathology. The degree of stage migration in the multidisciplinary team meetings (MDT) was assessed and training needs were identified.

53 patients (32 males) with a mean (SD) age of 56.7 (13.6) years with 54 rectal lesions and underwent trans-anal excision (n = 18) or upfront surgery (n = 35) were included. Pathology showed < / = pT1 stage in n = 18 and > / = pT2 stage in n = 36. Radio-pathological concordance rate was 38.9% and 74.1%, respectively, for primary reports and MDT reads, respectively, and during MDT, the rates improved by 44.5% and 30.5% for < / = pT1 and > / = pT2 stages ,respectively. The overall T-stage migration rate at MDT was 44.6% (25/54) and the migration rate was higher (61.1%) for < / = pT1 stage lesions. The best sensitivity, specificity, PPV, NPV and accuracy of MRI for T-staging was 83.3%, 91.6%, 83.3%, 91.6% and 88.8%, respectively.

Radio-pathological correlation for MRI T-stage is excellent for MDT reads by experienced radiologists. MDT reads lead to significant down-staging of T-stage in polyp and early rectal cancer thereby improving radio-path correlation.