As prognosis in breast cancer patients has been related to the AHH activity in their breast tissue, we have conducted a similar analysis on pulmonary drug metabolizing enzymes as prognostic markers for male lung cancer patients, primarily investigated for other reasons. A subset of 50 patients with lung cancer related to tobacco use, who had undergone thoracic surgery, was reanalyzed. The activity of parenchymal aryl hydrocarbon hydroxylase (AHH) and epoxide hydrolase (EH) that had been determined previously in homogenates of non-neoplastic surgical lung specimens, was used for comparisons of the patients' survival after surgery. When the crude mortality percentages at I and 2 years by A H H or EH activity, subdivided into quarters of the distribution, were calculated, a lower mortality was related to lower enzyme levels.
Subjects in the 1st and 4th quarters of the distribution showed significant differences in their I-year survival for A H H
(p = 0.05) and EH (p < 0.01) activities. This relationship could not be accounted for by age, cumulative lifetime smoking, recent or continuing smoking, stage or histological type of disease. Thus, the levels of pulmonary AHH and EH may have some prognostic significance in tobacco-related lung cancer.
Cigarette smoking is the strongest risk factor for lung cancer so far identified (IARC, 1986), but the large variation in individual cancer risk suggests that host factors, either inherited or acquired, play a role (Harris, 1987). Attempts have been made in the past to predict the lung cancer risk in smokers by measuring the inducibility of the enzyme aryl hydrocarbon hydroxylase (AHH) in haemagglutinin-stimulated lymphocytes (Kel-