Gastrointestinal Cancer Survival Among Atomic Bomb Survivors

Abstract

Radiation exposure is a strong, established risk factor for the development of several forms of cancer, including gastrointestinal cancers. However, few studies have investigated the relationship between pre-diagnostic radiation exposure and survival after cancer diagnosis. Using data from the Life Span Study (LSS) of atomic bomb survivors, we identified N=8,461 LSS participants diagnosed with a first primary invasive stomach or colorectal cancer (CRC) between 1958-2009. Cancer incidence data were linked with mortality data for years 1958-2014. Cox regression was used to calculate hazard ratios and 95% confidence intervals for associations of radiation dose due to atomic bomb exposure with overall survival (i.e., death from any cause) and gastrointestinal cancer-specific survival (i.e., death attributed to CRC or stomach cancer) after cancer diagnosis. Analyses were adjusted for age at diagnosis, year of diagnosis, and sex. Among LSS participants with a gastrointestinal cancer, data showed significantly more favorable survival for combined gastrointestinal cancers for individuals exposed to 0.50 – 0.99 Gy and modestly poorer survival among those exposed to higher levels of radiation (≥1 Gy) compared to those with no to very low exposure (<0.005 Gy), with associations differing across gastrointestinal cancer sites. Similar associations, although not statistically significant, were observed in stratified analyses restricted to those with stomach cancer and colon cancer. No associations were observed in analyses of LSS members with rectal cancer. In addition to the established increased risk of cancer, these results suggest that pre-diagnostic radiation exposure may affect survival after gastrointestinal cancer diagnosis for certain cancer sites.