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 (-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.