Local tumour invasion as a prognostic factor in colorectal cancer.

A prospective study was carried out of 404 patients with colorectal cancer who were followed up for a mean period of 42 months. Macroscopic extramural tumour invasion was found at laparotomy in 46 patients undergoing apparently curative surgery and the survival rate was significantly reduced in these patients. The site of primary tumour in the colon or rectum did not influence the incidence of local tumour spread, but local invasion was related to the incidence of lymph node metastases and histological grading of the tumour. A staging classification has been proposed based not on lymphatic metastases, but on the extent of local tumour penetration. This modified staging system combines the operative findings with pathological grading of the tumour and emphasizes the prognostic significance of local tumour invasion.