Radiation and lung cancer: epidemiological and genetic findings from studies among atomic-bomb survivors

Studies on the Japanese atomic-bomb survivors have been providing important knowledge on late effects of ionizing radiation exposure at low/moderate doses. In particular, the long-term follow-up in the Life Span Study (LSS) of survivors has played major roles to characterize the radiation-induced risks of various cancer and non-cancer outcomes. Lung cancer, the most common cancer worldwide and the second most in the LSS, is among those cancers strongly associated with radiation exposure. While numerous studies have linked radon and other types of radiation to lung cancer, questions remain about how smoking interacts with radiation for this predominant cause of death. It has not been clear how such joint effects differ by histological subtype of lung cancer. In addition, molecular mechanisms of the late effects of radiation exposure on lung cancer development are not clear, and thus there is considerable interest in the radiation-associated lung carcinogenesis, which is believed to involve multiple stages with potentially many genetic and epigenetic alterations. In attempts to find answers to these questions, some studies have been conducted with data of atomic-bomb survivors, a couple of which will be introduced in the following. (author)