Diagnostic radiation and testicular germ cell tumor risk.

Abstract

556 Background: Both incidence of testicular germ cell tumor (TGCT) and use of diagnostic radiation have increased in recent decades. In a quarter of diagnostic scans in children, direct and indirect radiation dose to the testes exceeds 20 mSv, which surpasses thresholds associated with malignancy risk (~5 mSv). Here, we examine the association between exposure to diagnostic radiation and TGCT risk in a case-control study. Methods: Cases were enrolled in a hybrid hospital- and population-based setting and controls were recruited from the community. Participants reported on exposures to x-ray/CT below the waist and lower GI series, and we derived a combined variable for any exposure. After imputation to infer missing data, we compared baseline characteristics and used multivariable logistic regression adjusting for age and race to determine the risk of developing TGCT according to number of exposures and age at first exposure. Results: As expected, cases (n = 1088) were more likely than controls (n = 1458) to be white, have a family history of TGCT, and have a history of cryptorchidism (p < 0.05). There was an increased risk of TGCT with a greater number of exposures for both x-ray/CT (ptrend= 0.002) and the combined diagnostic radiation variable (ptrend< 0.001). Compared to those without any exposure, risk was greatest among those reporting ≥6 exposures for x-ray or CT (OR, 9.6; 95% CI, 4.6-19.9; p < 0.001) and the combined variable (OR, 5.8; 95% CI, 3.2-10.4; p < 0.001), after adjusting for age at first exposure. Early first exposure before eleven years of age increased risk of TGCT for x-ray/CT (OR, 2.36; 95% CI, 1.17-4.77) and combined radiation exposure (OR, 1.96; 95% CI, 1.05-3.67) compared to later first exposure after seventeen years of age, adjusting for total exposures. Analyses limited to observed data only yielded similar results. Conclusions: Exposure to diagnostic radiation below the waist, particularly among younger individuals, may increase TGCT risk. These results should be validated. As the testes are present outside the body and rarely examined using diagnostic radiation, a unique opportunity for shielding exists. Efforts to reduce testicular dose and optimize shielding practices should be prioritized.