A case-control study for evaluating the efficacy of mass screening programfor lung cancer in Miyagi Prefecture, Japan

Background. In Miyagi Prefecture, a mass screening program for lung cancer has been conducted since 1982 (miniature chest X-ray for all screenees and sputum cytology for those with a smoking index greater than or equal to 600 ) [smoking index 600 = 30 pack years, the average number of cigarettes smok ed per day multiplied by the number of years of regular smoking]. Over 1500 lung carcinomas, including 250 roentgenographically occult lung tumors, we re detected and treated up to 1999. In the current study, a nested case-con trol study was conducted in the population that was screened in 1989 to eva luate the efficacy of the screening program for lung cancer. Methods. To reduce self-selection bias, the source Population was defined a s screenees with negative results in 1989 (284,226 individuals). In the pop ulation, 474 individuals died of lung carcinoma during 1992-1994. After exc lusion, 328 patients who died of primary lung carcinoma at between ages 40 years and 79 years were defined as the cases. Six controls were supposed to be selected in the source population for each case and matched by gender, year of birth, municipality, and smoking habits. Controls who had died or m oved before the matched case was diagnosed were excluded. Finally, 328 case s and 1886 controls were selected. Screening histories were compared, and o dds ratios were calculated using conditional logistic regression analysis. Results. Within the 12 months before diagnosis, 241 of 328 cases (73.5%) ha d attended the screening compared with 1557 of 1886 controls (82.6%). The s moking-adjusted odds ratio was 0.54 (95% confidence interval, 0.41-0.73). Conclusions. The mass screening program for lung cancer in Miyagi Prefectur e was capable of reducing by 46% the risk of death from carcinoma of the lu ng. Cancer 2001;92:588-94. (C) 2001 American Cancer Society.