Radiation risk of incident colorectal cancer by anatomical site among atomic bomb survivors: 1958–2009

Abstract

Radiation effects on colorectal cancer rates, adjusted for smoking, alcohol intake and frequency of meat consumption and body mass index (BMI) by anatomical subsite (proximal colon, distal colon and rectum) were examined in a cohort of 105,444 atomic bomb survivors. Poisson regression methods were used to describe radiation‐associated excess relative risks (ERR) and excess absolute rates (EAR) for the 1958–2009 period. There were 2,960 first primary colorectal cancers including 894 proximal, 871 distal and 1,046 rectal cancers. Smoking, alcohol intake and BMI were associated with subsite‐specific cancer background rates. Significant linear dose–responses were found for total colon (sex‐averaged ERR/Gy for 70 years old exposed at age 30 = 0.63, 95% confidence interval [CI]: 0.34; 0.98), proximal [ERR = 0.80, 95% CI: 0.32; 1.44] and distal colon cancers [ERR = 0.50, 95% CI: 0.04; 0.97], but not for rectal cancer [ERR = 0.023, 95% CI: −0.081; 0.13]. The ERRs for proximal and distal colon cancers were not significantly different (p = 0.41). The ERR decreased with attained age for total colon, but not for proximal colon cancer, and with calendar year for distal colon cancer. The ERRs and EARs did not vary by age at exposure, except for decreasing trend in EAR for proximal colon cancer. In conclusion, ionizing radiation is associated with increased risk of proximal and distal colon cancers. The ERR for proximal cancer persists over time, but that for distal colon cancer decreases. There continues to be no indication of radiation effects on rectal cancer incidence in this population.

Effect of Heterogeneity in Background Incidence on Inference about the Solid-Cancer Radiation Dose Response in Atomic Bomb Survivors

“…However, our primary objective was to study possible sources of, or causes of, curvature or lack of curvature in the estimated dose response for all solid cancers combined. Careful modeling is the goal of individual site-specific analyses that are ongoing (24–27). A fourth limitation is that, although several methods exist for accounting for random dosimetry error, including a Bayesian approach (16) and a simulation-extrapolation approach (28), we used only the method of Pierce et al (6) because our goal was to further understand the results of Grant et al .…”

Radiation and Risk of Liver, Biliary Tract, and Pancreatic Cancers among Atomic Bomb Survivors in Hiroshima and Nagasaki: 1958–2009

“…This study was conducted as part of an ongoing series of analyses regarding radiation risks for solid cancer in aggregate (25) and at major anatomical sites (26)(27)(28)(29). The study design and eligibility criteria were identical to those for the all-solid-cancer analysis (25).…”

Analyses of cancer incidence and other morbidities in gamma irradiated B6CF1 mice

“…The major source of data on whole-body human exposures to gamma radiation is the Life Span Study (LSS) cohort that includes over 120,000 survivors of the atomic bombing in 1945 [3][4][5][6]. While these data have been a remarkable resource for epidemiological studies determining risks associated with acute exposures [5,[7][8][9][10][11][12][13], extrapolation of health risks to humans exposed intermittently to lower doses of radiation remains uncertain. Different mathematical modelling approaches have been used over the past 50 years to extrapolate health risks but they were met with variable enthusiasm from the scientific community [1,[14][15][16][17][18].…”