Ectopic production of big ACTH in carcinoma of the lung. Its clinical usefulness as a biologic marker.

This report considers the potential usefulness of adrenocorticotropic hormone (ACTH) determinations in diagnosis and in prognosis for therapy of patients with carcinoma of the lung but without clinical Cushing's syndrome. The report is based on radioimmunoassay data from 129 patients, including 62 with lung cancers and 67 with nonmalignant pulmonary conditions. Elevated plasma ACTH was found in 21 of 24 patients with untreated cancer and the hormone was detected in tumor extracts and/or bronchial washings from the remaining 3. Elevation of plasma ACTH was found in only 10 of 38 treated patients. Absence of clinical Cushing's syndrome in spite of high plasma ACTH concentrations is explained by the observation that the predominant form of ectopic ACTH in plasma is immunoreactive but nonbioactive 'big' ACTH. Prolonged survival, for longer than 19 months, was observed in only 5 patients: all patients with low plasma ACTH after resection of the lung tumor and 2 of 3 patients with low plasma ACTH without therapy. ACTH was found in all available malignant tissue, primary and metastatic, from the lung carcinoma group,but not in normal lung or in 5 tumors metastatic to the lung. Of the 39 patients diagnosed initially to have chronic obstructive pulmonary disease, 14 showed plasma ACTH elevation. However, 3 of these patients with the highest concentrations subsequently manifested carcinoma or carcinoma in situ.