The significance of tumor markers for proliferation and apoptosis in predicting survival in colorectal cancer

PURPOSE: Clinicopathologic staging is even today the best prognostic factor in both colon and rectal cancers. There is still considerable variation in survival within the stages. To find other prognostic indicators we investigated six biologic markets associated with apoptosis and cell proliferation. METHODS: Formalin-fixed, paraffin-ernbedded tissue samples of 363 patients with primary colon or rectal cancer of Dukes Stages A to D were chosen for immunohistochemical staining of five tumor markets: bcl-2, p53, Ki-67, cyclin D1 and carcinoembryonic antigen. Also, the number of apoptotic cells was studied by the terminal deoxynucleotidyl transferase-mediated (D)-UTP nick end labeling method in 347 cases. The study was done on specially prepared tissue arrays. RESULTS: In rectal cancer, patients with a Ki-67 labeling index of 5 percent or higher had a better prognosis than those with it lower index. Also, positive cytoplasmic p53 expression predicted a favorable outcome in rectal cancer. In colon cancer, positive nuclear staining of cyclin DI reflected better survival. Weak and moderate staining of carcinoembryonic antigen correlated with better prognosis than strong staining, but negative staining predicted poor outcome. High apoptotic index of 100 or higher correlated with poor prognosis in colon cancer. However, in rectal cancer, the trend was the opposite. Bcl-2 staining tended to be more intense in samples of patients living 5 years or longer compared with those with worse prognosis. CONCLUSIONS: Colon cancer and rectal cancer seem to have different biologic behavior, at least with respect to apoptosis, cytoplasmic p53 expression, and perhaps Ki-67 and carcinoembryonic antigen. Further studies are needed to clarify the significance of these factors.