Evaluation of squamous cell carcinoma antigen as a new marker for lung cancer.

Carcinoembryonic antigen (CEA) is the only tumor marker of proven, although limited, value for the management of patients with non-small cell lung cancer (NSCLC). The authors have prospectively assessed the potential value of a new tumor marker, squamous cell carcinoma antigen (SCC Ag), in a large series of patients with advanced lung cancer (LC). Squamous cell carcinoma antigen and CEA levels were measured in 382 healthy persons (N1 group), 90 patients with benign pulmonary diseases, and 291 patients with LC (129 with SCLC and 162 with NSCLC, including 96 with squamous LC). Carcinoembryonic antigen levels were higher in smokers than in nonsmokers, but smoking habits did not influence the serum concentrations of SCC Ag. Elevated values (above the 95th percentiles of N1, i.e., 7.5 ng/ml for CEA and 3.0 ng/ml for SCC Ag) were observed in 11.1% of patients with benign pulmonary diseases for both markers. Carcinoembryonic antigen was more sensitive than SCC Ag, even for squamous LC (56% versus 35% of elevated values, P less than 0.01). The specificity toward squamous LC was better, however, for SCC Ag, for which levels were elevated in only 8.5% of SCLC and in 18% of other forms of NSCLC, compared with 49% and 55%, respectively, for CEA. Moreover, measurement of SCC Ag and CEA levels did not give redundant information: thus, in squamous LC and SCC Ag level was elevated in 32% of the patients with a normal CEA level, increasing from 57% to 71% the proportion of patients with at least one elevated marker. Lastly, elevation of CEA or SCC Ag levels was an adverse prognostic factor in squamous LC (P = 0.05 for CEA; P = 0.07 for SCC Ag). In conclusion, SCC Ag appears to be worthwhile of further investigation in squamous LC. The authors found that this new marker provided additional information on CEA and that it was more specific for squamous LC than CEA.