Screening for lung cancer--results from a case-control study.

By means of a case-control study, a screening programme originally introduced to control tuberculosis and utilizing biennial chest X-rays (70 X 70 pa.) was evaluated for its effect on lung cancer mortality. The case group consisted of 130 population-based deaths from lung cancer (males below 70). One general population-based and one hospital-based control group were used, both consisting of 260 males matched for age and alive at the same time as the relevant case. The proportion of exposed persons, i.e. those having had at least one screening test within the 2 years preceding diagnosis, was similar in the case group and in the 2 control groups: 76, 78 and 75%, respectively. The relative risk of lung cancer death was 0.9 and 1.1 (95% confidence intervals 0.5 to 1.5 and 0.7 to 1.8). There was no trend in relative risks with regard to the number of tests performed and the interval since the last test.