Tar yields of cigarettes and male lung cancer risk.

Of 252 male lung cancer patients, 248 or 98% were cigarette smokers, significantly (P less than .001) more than in the control group (526 = 64% of 839). In relation to the relative risks (RR) of never-smokers, the adjusted (for age, total years smoked, and average number of cigarettes smoked per day) lung cancer RR for smokers who had exclusively smoked cigarettes belonging to group II (15-24 mg tar/cigarette) was 10.4 (P less than .001); for smokers who had exclusively smoked cigarettes belonging to group III (greater than 24 mg tar/cigarette), it was 25.1 (P less than .001). The respective RR of smokers who had mainly smoked cigarettes belonging to group I (less than 15 mg tar/cigarette), group II, or group III were 10.9 (P less than .001), 20.6 (P less than .001), and 36.7 (P less than .001). After the differences in daily consumption were taken into account, the adjusted (for age and total years smoked) lung cancer RR for smokers who had consumed mainly cigarettes belonging to the various groups were the following: group II (11-20 cigarettes/day) compared to group III (11-20 cigarettes/day), RR = 0.6 (P less than .05); group II (greater than 20 cigarettes/day) compared to group III (greater than 20 cigarettes/day), RR = 0.8; group II (greater than 20 cigarettes/day) compared to group III (11-20 cigarettes/day), RR = 1.3 (P less than .001); group II (greater than 20 cigarettes/day) compared to group III (less than 10 cigarettes/day), RR = 7.8 (P less than .001); and group II (11-20 cigarettes/day) compared to group III (less than 10 cigarettes/day), RR = 2.5 (P less than .001).