The prognostic information provided by preoperative serum CEA, CA 19-9 antigen assays as compared with the classical prognostic factors (age, sex, tumor infiltration, tumor stage (Dukes') and R-classification) in 495 patients with colorectal carcinoma was analysed.
Patients and methods: Survival function estimates were calculated according to Kaplan-Meier. The patients were separated into two groups according to the preoperative marker levels. Fixing specificity at 100% for healthy people, cut off levels were calculated. Survival curve differences were assessed using the log-rank-test. Multivariate Cox's proportional hazard regression analysis was performed. The Mantel-Haenszel method was used to assess the survival rate of patients with colorectal carcinoma and high versus low levels of tumor-associated antigens according to tumor stages. The study was performed on the frozen sera (stored at -80 degrees C) of 495 patients with histologically proven colorectal carcinoma.
Results: The Dukes' stages (log-rank chi-square = 231.9; P < 0.0001) represent the best prognostic factor besides the preoperative values of CA 19-9 (log-rank chi-square = 162.5). CEA shows a log-rank chi-square of 71.4. Thus, CEA and CA 19-9 can be used to discriminate two groups of patients with significantly different survival times (P < 0.0001). The importance of different parameters in providing additional prognostic information was evaluated by multivariate analysis (Cox's model). Estimated relative risks of death adjusted for tumor stage were 5.5 for Dukes' stage A versus Dukes' stage B/C and Dukes' stage B/C versus Dukes' stage D, respectively and an increasing relative risk of 27.5 for Dukes' stage A versus Dukes' stage D (P < 0.001). The relative risk for preoperative CA 19-9 serum concentrations (> or = 60 U/mL versus < 60 U/mL) was 2.3 (P < 0.001) for preoperative CEA concentrations (> or = 4 ng/mL versus < 4 ng/mL) 1.4 (P < 0.07). For CEA the 2-years survival rates in the group of patients with preoperative serum concentrations > or = 4 ng/mL versus < 4 ng/mL and Dukes' stage D were 16% versus 38%, in Dukes' stage B/C 73% versus 91% and in Dukes' stage A 100% versus 98%. For CA 19-9 the 2-years survival rates in the group of patients with preoperative serum concentrations > or = 60 U/mL versus < 60 U/mL and Dukes' stage D were 10% versus 39%, in Dukes' stage B/C 58% versus 87%. In the group of patients with Dukes' stage A with serum levels > or = 60 U/mL a 2-year survival rate of 100% was found. In the corresponding group only one patient exists.
Conclusion: The postoperative Dukes' classification provides the best prognostic information besides the preoperative values of CA 19-9. The predictive information provided by the preoperative CA 19-9 serum level is additional to that obtained from the other factors investigated.