Prognostic factors in colonic cancer.

Prognostic variables in 251 'curative' specimens of colonic cancer were studied. Subjective variables--tumour type, grade of differentiation, character of invasive margin and lymphocytic infiltration--were associated with fair to excellent levels of inter-observer agreement. Variables found to be of prognostic significance by univariate analysis were subjected to Cox regression analysis. This was undertaken for all three observers and for a consensus grading. No case in which direct spread in continuity was limited to the bowel wall was associated with a cancer-related death; 63 such specimens were removed as a group with an excellent prognosis and did not require further stratification. In the remaining 188 cases, all showing extramural spread, only lymph node invasion, character of invasive margin and tumour type were independent prognostic variables. The model differs from that developed previously for rectal cancer and is superior to the Dukes classification.