The utility of monitoring carcinoembyronic antigen during systemic therapy for advanced colorectal cancer.

To determine if pre-treatment serum carcinoembryonic antigen (CEA) levels or changes in CEA values during treatment have prognostic value, we reviewed five prior fluorouracil/leucovorin-based trials and identified 125 colorectal cancer patients with no prior chemotherapy for metastatic disease in whom CEA values were available. Although pre-treatment serum CEA values did not predict for clinical response or time to progression, serial monitoring of CEA appeared to be useful in patients with an elevated pre-treatment CEA, particularly when a decrease in CEA occurred in concert with radiographic evidence of disease response. The CEA nadir was a strong prognostic variable with respect to time to disease progression. A consistent rise in CEA values over the minimum value signals the need for radiographic re-assessment of the patient's disease status to rule out disease progression.