Lung Cancer in the Elderly: The Most Dominant Cause of Cancer Death in Japan

Lung cancer is a major cause of cancer-related death in Japan, and the overall survival rate was still poor. The majority of individuals diagnosed with lung cancer are elderly people aged ≥65 years. Although chronic inhalation of cigarette smoke is a major risk factor to the development of lung cancer, genetic factors have been implicated to account for some of the observed differences in lung cancer susceptibility. A number of studies have examined lung cancer susceptibility based on the presence of high-frequency, low-penetrance genetic polymorphisms. As exposure to harmful chemicals or reactive oxygen species via cigarette smoking is thought to contribute to the development of lung cancer, genetic polymorphisms involved in xenobiotic metabolism, DNA repair, and inflammation might be promising candidates. In order to evaluate whether the impact of genetic polymorphisms on lung cancer differs between elderly and younger people, we evaluated potential 31 genetic polymorphisms in a stratified analysis by age category (aged ≥65 and <65 years). Seven polymorphisms, namely, CYP1A1 rs4646903, CYP1A1 rs1048943, GSTM1 deletion, GSTP1 rs1695, SULTA1 rs9282861, TP53BP1 rs560191, and CRP rs2794520, were associated with lung cancer risk in the elderly. However, there was little difference in the impact of polymorphism on lung cancer risk between the elderly and non-elderly groups. In this chapter, we would like to discuss the importance of the prevention of smoking (the best established and strongest avoidable risk factor) at early age for successful aging.