Slope analysis of the postoperative CEA time course and its possible application as an aid in diagnosis of disease progression in gastrointestinal cancer

The postoperative carcinoembryonic antigen (CEA) time courses of patients with histologically proven adenocarcinoma of the gastrointestinal tract were analyzed to establish a possible correlation with distinct types of disease progression. The diagnosis of tumor progression was obtained by second-look surgery, and in some cases by other clinical diagnostic procedures. In thirty-one of thirty-four patients studied, tumor progression correlated with increasing CEA levels. The calculation of the slopes of the CEA increase in the computerized CEA surveillance diagrams represented a parameter that discriminated between local tumor recurrence and widespread tumor dissemination. All localized tumor recurrences exhibited a flat slope in the range of 0.08 to 0.30 ng CEA increase/ml serum within ten days, with a mean value of 0.17 ng/ml in ten days. The CEA slopes in cases of liver metastases were relatively steep and ranged from 0.9 to 3.8 ng/ml in ten days, yielding a mean slope of 2.2 ng CEA increase/ml serum in ten days.