Thymidine kinase (TK), carbohydrate antigen 19-9 (CA 19-9), carbohydrate antigen 125 (CA 125), squamous cell carcinoma antigen (SCC) and tissue polypeptide antigen (TPA), were evaluated in 104 untreated patients with primary lung cancer acid 55 patients with benign lung disease. The mean concentrations of TPA and CA 125 were significantly higher in lung cancer patients than in benign controls (p<0.001). The concentrations of all the tumor markers were well correlated with the stage of lung cancer. In respect to sensitivity, specificity and accuracy, TPA was superior to the other tumor markers tested (70.2%, 88.8% and 75.8% respectively). When TPA was combined with the other markers, sensitivity increased from 70.2% to 98%, but as the number of combined markers became larger, specificity decreased (from 88.8% to 40%). Nevertheless, the combination of TPA and CA 19-9 showed significantly higher sensitivity in patients with resectable non small eel lung cancer (NSCLC) and limited small cell lung cancer (SCLC) than TPA alone (87% vs 49% and 88.8% vs 44.4% respectively) without significant differences in specificity. The relative possibility of lung cancer was 15% when one tumor marker was positive. This possibility increased to 82%-100% when more than three markers were positive.

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