Histopathological regression grading versus staging of rectal cancer following radiotherapy

Aims: To compare histological grading of rectal cancer radiotherapy response with pathological staging as a prognostic indicator. Methods: Histological tumour regression was five tier graded in 102 rectal cancer patients treated with preoperative radiotherapy [short course (n=34), long course (n=68)]. Differences between these grades and between the two radiotherapy regimes were assessed. These variables, pTMN staging and others were correlated with relapse free survival at 3 years. Results: 22 patients suffered disease recurrence and four died during a mean post-operative follow-up of 40.3 months. There were 52 good responders (tumour regression grades 1-3) and 50 poor responders (tumour regression grades 4-5). Regression was greater following the long course regime ( p<0.0001). Otherwise, there were no significant differences between the response groups and between the two regimes, including the number of lymph nodes found in the resected bowel. Only the pN status correlated with relapse free survival on multivariate analysis ( p=0.0004; HR =4.26, 95%CI=1.66-10.93 for pN2 versus pN0). Conclusions: The number of lymph nodes found for staging was not influenced by either the extent of primary tumour regression or the type of radiotherapy. pN status, but not tumour regression grade, is a reliable predictor of survival.