[A Decrease in Lung Cancer Mortality Following the Implementation of CT Screening for General Population].

In Hitachi Medical Area, a large-scale lung cancer screening program using low-dose CT has been underway in two medical facilities since its introduction in 1998 and 2001. A total of 61,914 tests were performed among 25,385 participants until 2006. Two hundred and ten lung cancer patients had been identified on CT screening. The estimated 5-year survival rate for all patients was 90%. Among residents in Hitachi City, nearly 40% of inhabitants aged 50-69 years were estimated to have participated in the screening from 1998 through 2009. Cancer mortality data were obtained from a regional cancer registry and the standardized mortality ratio (SMR) of lung cancer was calculated for each 5-year period during 1995-2009. For residents aged 50-79 years, SMR was nearly unity between 1995 and 2004; however, there was a significant decrease during 2005-2009, with SMR (95% confidence interval) being 0.76 (0.67-0.86). These results suggest that the wide implementation of CT screening may reduce lung cancer mortality in the community, 4-8 years after introduction. It is desirable to continue to focus on future developments, including original research in Japan.