Serial plasma carcinoembryonic antigen measurement for monitoring patients with advanced lung cancer during chemotherapy.

The plasma carcinoembryonic antigen (CEA) levels in 243 patients with untreated advanced lung cancer were studied to assess their value for prognosis and for indicating the effectiveness of chemotherapy. Of patients with adenocarcinoma, small cell carcinoma, squamous cell carcinoma, and large cell carcinoma, 43%, 24%, 7%, and 13%, respectively, had elevated CEA levels of 20 ng/ml or greater before treatment. Pretreatment CEA levels were elevated to above 20 ng/ml for 38% of 163 patients with extensive disease and for 22% of 80 patients with limited disease (P less than 0.02). In patients with adenocarcinoma of the lung, the pretreatment CEA levels were not correlated with response to chemotherapy and patients' survival. Serial measurement of plasma CEA was a useful noninvasive technique for monitoring the response to chemotherapy in patients whose pretreatment levels were 20 ng/ml or higher. All of 18 patients with complete or partial responses and 5 of 6 patients with minor responses showed greater than 36% decrease in the CEA level compared with the pretreatment level. In all of nine patients with progressive disease, the CEA levels increased after chemotherapy. Therefore, an increase of greater than 36% beyond the baseline level was a useful guideline criterion for a significant change for determination of tumor response to chemotherapy, although 41% of 22 patients with stable disease exceeded the pretreatment level by 36% or more in either direction (mean percent change +/- standard deviation, -4.1% +/- 52.2%), and 4 of 9 patients with progressive disease did not have levels greater than 36% above the baseline levels.