Plasma angiotensin-converting enzyme activity in patients with bronchial carcinoma

Plasma angiotensin-converting enzyme (ACE) activities were measured in 58 consecutive patients presenting with bronchial carcinoma. The mean ACE activity before treatment was significantly lower than that of a control population (P less than 0.005). There was a significant and direct relationship between the initial plasma ACE activity and survival time (P less than 0.01) which could not be explained by further analysis for age, clinical staging, or respiratory function, as judged by % FEV. There was a significant increase in plasma ACE activity (P less than 0.03) in nine patients with three or more plasma samples after treatment with chemotherapy or radiotherapy. These results suggest that low plasma ACE activity is associated with poor prognosis in bronchial carcinoma.