Low-dose occupational ionising radiation exposure and gastrointestinal cancer mortality among US radiologic technologists, 1983-2021

Objectives We evaluated the relationship between cumulative occupational ionising radiation exposure and gastrointestinal cancer mortality in a cohort of US radiologic technologists (USRT). Methods Among 106 072 USRT cohort participants who were cancer-free at completion of the baseline questionnaire (1983-1998, representing completion of the first (1983-1989) or second questionnaire (1994-1998) as baseline), protracted low- to moderate-dose occupational ionising radiation exposure was evaluated in relation to gastrointestinal cancer mortality over the follow-up period (through 2021). Poisson regression was used to calculate linear excess relative rates (ERR) of gastrointestinal cancer mortality per 100 mGy colon-absorbed dose (mean=15 mGy; range 0-754 mGy), lagged 10 years, adjusting the baseline mortality rate for attained age, sex, birth cohort, race and other potential confounders (alcohol consumption, smoking, body mass index, non-steroidal anti-inflammatory drug (NSAID) use). Results Over follow-up (mean=31.4 years), 570 pancreatic, 504 colon, 171 liver, 131 oesophageal, 106 stomach and 73 rectal cancer deaths were identified. In the full cohort, no significant dose-response relationships were observed for pancreatic, colon, liver, oesophageal or rectal cancer mortality. A non-significant positive association for stomach cancer mortality was observed in a model minimally adjusted for attained age, sex and birth cohort; however, this association was attenuated after additionally adjusting for race and NSAID use (ERR/100mGy=1.56; 95% CI <0 to 159). Evidence for effect modification for stomach cancer mortality was observed by birth year (P-interaction=0.002) and year first worked (0.004), although based on small number of deaths, most positive associations within categories were not statistically significant. Conclusions In this nationwide cohort of radiologic technologists, cumulative occupational ionising radiation exposure was not clearly associated with mortality from specific gastrointestinal cancers. Studies with cancer incidence follow-up and pooled analyses of ionising radiation-exposed populations may provide more comprehensive and robust dose-response estimates for specific gastrointestinal cancers.