MRI rectal cancer in Australia and New Zealand: An audit from the PETACC-6 trial

Introduction: An MRI audit substudy was conducted in patients who underwent an MRI prior to treatment in Australia and New Zealand as part of the PETACC-6 trial in locally advanced rectal cancer. Methods: A total of 82 patients from 15 centres had rectal MRI scans reviewed for technique, data included in reports and comparison of reports with blinded central reporting by two experienced radiologists. Results: In total, 82% performed minimum T2 sagittal and T2 axial oblique sequences. The high-resolution T2 sequence parameters varied significantly with only 33% obtaining a voxel size of <1.3 mm(3). The rate of inclusion of relevant findings in the reports was T3 distance in mm 21%, N stage 84%, circumferential resection margin ( CRM) status 72%, extramural venous invasion ( EMVI) status 29% and distance from the puborectalis sling 17%. In total, 31% reports included all of T stage with T3 substage, N stage and CRM involvement. In total, 17% reports included these 3 findings and EMVI. Eleven reports used a template with 82% of these including the first 3 findings. The agreement with central reporters was T stage 76%, N stage 70%, CRM status 57% and EMVI 16%. Conclusion: There is significant variation in scan quality and low rates of including all relevant findings in rectal MRI reports in the audit. The authors recommend adoption of routine sequences and template reports in both trial settings and routine practice to improve scan technique and adequacy of reports in rectal cancer MRI staging scans across Australia and New Zealand.