Individualized Cutoff Value of the Preoperative Carcinoembryonic Antigen Level is Necessary for Optimal Use as a Prognostic Marker

PURPOSE Carcinoembryonic antigen (CEA) is an important prognostic marker in colorectal cancer (CRC). However, in some stages, it does not work. We performed this study to find a way in which preoperative CEA could be used as a constant prognostic marker in harmony with the TNM staging system. METHODS Preoperative CEA levels and recurrences in CRC were surveyed. The distribution of CEA levels and the recurrences in each TNM stage of CRC were analyzed. An optimal cutoff value for each TNM stage was calculated and tested for validity as a prognostic marker within the TNM staging system. RESULTS The conventional cutoff value of CEA (5 ng/mL) was an independent prognostic factor on the whole. However, when evaluated in subgroups, it was not a prognostic factor in stage I or stage III of N2. A subgroup analysis according to TNM stage revealed different CEA distributions and recurrence rates corresponding to different CEA ranges. The mean CEA levels were higher in advanced stages. In addition, the recurrence rates of corresponding CEA ranges were higher in advanced stages. Optimal cutoff values from the receiver operating characteristic curves were 7.4, 5.5, and 4.5 ng/mL for TNM stage I, II, and III, respectively. Those for N0, N1, and N2 stages were 5.5, 4.8, and 3.5 ng/mL, respectively. The 5-year disease-free survivals were significantly different according to these cutoff values for each TNM and N stage. The multivariate analysis confirmed the new cutoff values to be more efficient in discriminating the prognosis in the subgroups of the TNM stages. CONCLUSION Individualized cutoff values of the preoperative CEA level are a more practical prognostic marker following and in harmony with the TNM staging system.