[The usefulness of the quantitative evaluation of the plasma levels of the carcinoembryonic antigen (CEA) in patients with respiratory neoplasms (author's transl)].

Plasma concentration of the carcinoembryonic antigen (CEA) was determined by radioimmunoassay in 80 patients affected with different neoplasms of the respiratory system, among which the most predominant was bronchial carcinoma. For this type of tumor the results showed a percentage of positivity of 69 percent, with a greater value in the disseminated neoplasias (81 percent) in comparison with those which were localized (48 percent). The concentrations of the antigen were greater in the metastatic tumors; in 55 percent of the cases levels above 40 ng/ml were observed. On the other hand this figure was reached only by 4 percent of the localized tumors. Values of the antigen higher than 40 ng/ml should lead to the suspicion of the existence of neoplastic widespread. Among the rest of the series the negativity noticed in all the cases of pleural mesothelioma stands out, and indicates that this type of tumors does not produce CEA.