Time‐dependency of the prognostic effect of carcinoembryonic antigen and p53 protein in colorectal adenocarcinoma

BACKGROUND This study examined the prognostic information regarding the risk of postoperative tumor recurrence obtained by simultaneous determination of preoperative serum carcinoembryonic antigen (CEA) and immunohistochemical expression of p53 protein in tumor tissue from patients with colorectal carcinoma. METHODS A retrospective study of 174 patients (AJCC/UICC Stages I, II and III) was conducted. Serum CEA levels were determined by an enzyme-linked immunoadsorbent assay. Immunohistochemical expression of nuclear p53 protein was assessed in formalin fixed, paraffin embedded archival tumor tissue. The results of both factors were categorized by clinical and histopathologic variables. The relative prognostic significance of all factors with regard to disease free survival was assessed by Cox proportional hazards regression analysis. The stability of the predictive value of both markers was assessed: 1) by splitting the follow-up into three intervals and performing separate analyses for each period and 2) graphically by plotting the corresponding cumulative hazards ratio along the follow-up. RESULTS Eighty-two (47%) tumors manifested overexpression of p53 protein and 60 tumors (34.4%) exhibited elevated serum CEA levels (cutoff value of 5 ng/mL). p53 positive immunostaing and elevated CEA levels were associated with low cumulative disease free survival at 60 months' of follow-up, and proved to have independent prognostic significance. Analysis performed in different time periods of follow-up showed that the prognostic effect of both markers was not stable over time. The predictive significance of CEA and p53 changed along the study periods. An elevated preoperative CEA level was an indicator of a high risk of recurrence only during the first 2 years after surgery (hazards ratio, 3.26; 95% confidence interval [95% CI], 1.65–6.42). The presence of p53 immunoreactivity in the primary tumor was an indicator of a high risk of recurrence only after the first year of follow-up (hazards ratio, 4.02; 95% CI, 1.68–9.6). CONCLUSIONS The serum CEA level and expression of p53 protein provide complementary prognostic information. Time-dependency of the prognostic influence of both parameters should be taken into consideration when establishing postoperative predictive estimations. Cancer 2000;88:35–41. © 2000 American Cancer Society.