Pulmonary function as a predictor of lung cancer mortality in continuing cigarette smokers and in quitters

Background Forced expiratory volume in 1 second (FEV1) may be useful for identifying smokers at higher risk of lung cancer. We examined the association of FEV1 with lung cancer mortality (LCM) among cigarette smokers in the Multiple Risk Factor Intervention Trial (MRFIT). Methods In all, 6613 MRFIT baseline smokers alive at trial end in 1982 had acceptable FEV1 measures and complete smoking history; men were classified as during-trial long-term quitters (N=1292), intermittent quitters (1961), and never quitters (3360). Proportional hazards models for LCM were fit with quintiles of average FEV1, adjusted for age, height, race, smoking history, and other risk factors. Results For long-term, intermittent, and never quitters respectively, mean baseline cigarettes/day was 28, 32, and 35; trial-averaged FEV1 was 3201, 3146, and 3082 ml; and average decline in FEV1 was -46.0, -54.6, and -62.5 ml/year. With median post-trial mortality follow-up of 18 years, there were 363 lung cancer deaths. Age-adjusted LCM rates varied across FEV1 quintiles from 50 (lowest quintile) to 11 (highest quintile), 58 to 11, and 76 to 20, per 10 000 person-years, for long-term quitters, intermittent quitters, and never quitters, respectively. Multivariate adjusted hazard ratios for 100 ml higher FEV1 were 0.92 [P=0.004], 0.95 [P=0.003], and 0.95 [P<0.0001] respectively. Conclusions These results demonstrate the strong predictive value of FEV1 for lung cancer among cigarette smokers independent of smoking history; results did not differ by during-trial quit status. FEV1 may be a biological marker for smoking dose or it may be that genetic susceptibilities to both decreased FEV1 and lung cancer are associated.