Repeated exposures to diagnostic imaging, such as X-rays and computerized tomography (CT) scans, may increase the risk of testicular germ cell tumor (TGCT), according to a new study.

Researchers at the University of Pennsylvania (Penn; Philadelphia, USA), the Lee Moffitt Cancer Center and Research Institute (Tampa, FL, USA), and other institutions conducted a case-control study of 315 men with and 931 men without TGCT, recruited from hospital- and population-based settings. Study participants reported on exposures to x-ray or CT below the waist and lower gastrointestinal (GI) series or barium enema, which include a series of x-rays of the colon. Adjusted risk of TGCT was then calculated according to number of exposures and age at first exposure.

The results revealed that after adjustment for known risks of testicular cancer, including cryptorchidism and family history, race, age, and other factors, there was a statistically significant increased risk (59%) of TGCT among those reporting at least three exposures to X-ray, including a colon X-ray, and CT below the waist, compared to men with no such exposure. TGCT risk was also elevated for those exposed to diagnostic radiation during the first decade of their life, compared to those first exposed at age 18 years or older. The study was published on November 11, 2020, in PLOS One.

“The steady rise in TGCT cases over the past three or four decades suggests there is an environmental exposure risk at play, but no definitive risk factor has ever been identified,” said senior author Professor Katherine Nathanson, MD, of Penn. “Our data suggests that the increased use of diagnostic radiation below the waist in men over that same time may contribute to the increase in incidence. If our results are validated, efforts to reduce medically unnecessary and avoidable testicular exposure should be considered.”

TGCT is the most common cancer in white men aged 15–44 years of age, and incidence has increased rapidly in recent decades, particularly among those of European ancestry. Although multiple hypotheses investigating the impact of environmental exposures on risk of TGCT have been proposed, few were found to be robustly associated with the increasing incidence. One factor contributing to the rise in TGCT incidence may be the 20-fold increased use of diagnostic radiation in recent decades.

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