Study supports testicular shielding and efforts to reduce radiation in men and children during diagnostic scans.
X-rays and CT scans can be critical diagnostic tools. But, for men who are exposed to the radiation repeatedly or early in their lives, these imaging studies can increase the risk of testicular cancer by more than half.
Testicular germ cell tumor (TGCT) is the most common form of cancer in younger men, ages 15 to 45 – and the incidence is rising. In 1975, only three in 100,000 men were diagnosed. But, today, six out of every 100,000 men get the diagnosis with nearly 9,500 cases expected by the end of 2020. However, the reason behind the spike has been unclear.
A team from Penn Medicine set out to find out what the cause might be. They published their results, which could lead to changes in how these imaging scans are conducted, on Nov. 11 in PLOS ONE.
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“The steady rise in testicular germ cell tumor 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 Katherine L. Nathanson, M.D., deputy director of Penn Medicine’s Abramson Cancer Center. “Our data suggest that the increased use of diagnostic radiation below the waist in men over that same time may contribute to the increase in incidence.”
Currently, there is limited data looking at how the diagnostic radiation from X-rays and CT scans in clinical care could be involved in TGCT, said Nathanson, who is also the Pearl Basser Professor of BRCA-Related Research at the University of Pennsylvania Perelman School of Medicine. Instead, previous studies have examined the impact of occupational exposures, such as from the military or nuclear workers.
Consequently, to pinpoint whether these studies do, in fact, affect the development of TGCT, the team, that was led by Kevin Nead, M.D., before he moved from Penn Medicine to MD Anderson Cancer Center, conducted an observational study that included 1,246 men between ages 18 and 55 who both did and did not have testicular cancer. Participants provided details, via questionnaire, on any imaging prior to diagnosis conducted during their lifetimes, including body location and number of exposures. Tumor samples were also included.
Based on their evaluations, the team discovered that diagnostic radiation exposure did create a statistically significant increase in the risk for testicular cancer. After adjusting for known risk factors for the disease, including cryptorchidism, family history, age, and race, they found that men with at least three exposures to X-ray, including colon X-ray, and CT below the waist had a 59-percent increased risk for TGCT than men who received no diagnostic radiation. The risk was also higher for men who had these scans during their first 10 years of life.
“If our results are validated, efforts to reduce medically unnecessary and avoidable testicular exposure should be considered,” the team said, “in part through efforts to reduce radiation dose and optimize shielding practices when appropriate.”