Angiotensin-I-converting enzyme in cancer patients

Serum levels of angiotensin-I-converting enzyme (ACE) were assayed before, during, and after radiation therapy in 209 patients receiving treatment for neoplastic disease. Daily fluctuations in the measured ACE levels were minimized by comparing all patient values to that of a simultaneously run sample from a standard source of serum obtained by pooling sera from young, healthy volunteers. Most of the patients tested presented with a normal to low ACE level, with the mean value for all patients being 70% of the standard value. More patients with primary lung cancer displayed values that were low (107 of 120) than did patients with disease outside the lung (44 of 78), this difference being statistically significant at p less than 0.001. In addition, more patients with lung cancer had values less than 70% of the standard than did patients with disease outside the lungs. These initial results suggest that monitoring of serum ACE levels may be useful in the management of patients with malignant disease in the lung.