AIM: A three-grade system for macroscopic evaluation of the resection plane is used to describe the quality of total mesorectal excision (TME). In several studies, two of the three grades have been combined when analysing the outcome. The aim of our study was to compare the predictive value of the three-graded with that of a two-graded TME score.
METHOD: The quality of TME in 1382 patients who underwent elective resection for mid or low rectal adenocarcinoma was registered by 65 hospitals in PROCARE, a Belgian multidisciplinary improvement project. Prediction of outcome based on the classic three-grade score was compared with a two-grade scoring system in which intramesorectal resection (IMR) was combined with mesorectal (MRR) or with muscularis propria resection (MPR). End-points included the local recurrence rate, distant metastasis rate (DMR), disease-free survival (DFS) and overall survival (OS).
RESULTS: Among the 1382 resections, 63% were MRR, 27% IMR and 9% MPR. No significant differences were found in local recurrence between the different grades of TME. A two-grade score distinguishing MRR from the others was found to predict DMR, DFS and OS as well as the three-grade score.
CONCLUSION: The discriminatory and predictive value of a two-grade score, differentiating MRR from the combined IMR and MPR, was as good as the classic three-grade score.