Carcinoembryonic antigen: a useful prognostic marker in small-cell lung cancer.

Plasma carcinoembryonic antigen (CEA) was determined in 180 patients with small-cell lung cancer (SCLC) before treatment. An abnormal level (greater than or equal to 6 ng/mL) was found in 34% of patients tested. Patients with extensive disease (39/83) had a significantly higher frequency of abnormal CEA (P = .001) than those with limited disease (22/97). There was a strong correlation between obtaining an objective response--particularly a complete response (P = .00003)--and the absence of an elevated CEA. Patients with an abnormal CEA also had a shorter survival time (P = .0007) and the difference remained statistically significant after logrank adjustment for extent of disease and ECOG (Eastern Cooperative Oncology Group) performance status. There was also a negative correlation between survival time and the quantitative level of CEA. In this series, only the group of patients with normal initial CEA levels included all survivors beyond 2.5 years. We conclude that CEA is a useful prognostic factor in SCLC.