Exposure to procedural ionizing radiation and cancer risk among physicians

Abstract

Background. Physicians in certain specialities are routinely exposed to procedural ionizing radiation. Their risk of cancer is unknown, including by cancer sub-types. Aims. To assess cancer risk among exposed physicians. Methods. This population-based case–control study was completed in Ontario, Canada, where healthcare is universal, using linkage of physician billing claims to a province-wide cancer registry. Up to five cancer-free physician controls were matched to each cancer-affected physician, by sex, and both age at and year of, entry into practice. Cumulative exposure to procedural ionizing radiation was captured by physician billing claims. Conditional logistic regression generated an odds ratio (OR) of cancer per 1000 procedures performed and as a binary exposure comparing physicians above the upper 95th percentile cumulative number of procedures (≥200) to those below this cut point. Results. Mean (standard deviation) age of the 1265 cases and 5772 non-cancer controls was 39.7 (10.7) and 37.7 (9.0) years, and 45% and 49% were female, respectively. After a median (interquartile ranges) of 13.0 (6.9–20.4) and 12.5 (6.5–20.1) years of lookback among cases and controls, the OR of cancer was 1.02 (95% confidence interval 0.99–1.05; P = NS) per 1000 additional procedures performed. Modelling the cumulative exposure to procedures nonlinearly did not change the observed association (P > 0.40 for each). Comparing physicians above versus below the upper 95th percentile cumulative number of procedures, the OR of cancer was 1.23 (95% confidence interval 0.75–2.01, P = NS). Conclusions. Physician exposure to procedural ionizing radiation was not associated with a higher risk of cancer. Measures that minimize radiation exposure should continue.