November 16, 2020
Early and repeated exposure to radiation from diagnostic tests, such as X-rays and CT scans, may heighten the risk of developing testicular cancer, according to a new study from researchers at the University of Pennsylvania.
The incidence of testicular cancer has risen significantly in the United States and Europe over the past several decades, from about 3 in 100,000 men in 1975 to 6 in 100,000 men by 2020. About 9,500 American men and boys are diagnosed each year, usually between the ages of 15 and 45.
Much of the increase in diagnoses is linked to testicular germ cell tumor cases, but research into what has caused this trend has generally been limited to occupational exposure, such as in military and nuclear facility settings.
"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 Katherine L. Nathanson, deputy director of Penn’s Abramson Cancer Center and senior author of the new study. "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."
Radiation, a known risk factor for cancer, can damage DNA, resulting in genetic mutations. Use of diagnostic radiation comes with risks, but is often an important tool in identifying health issues.
Penn researchers conducted an observational study of 1,246 men between the ages of 18 and 55 with and without testicular cancer. The men completed a questionnaire covering their history of diagnostic testing along with other known and presumptive risk factors for testicular cancer. Tumor samples were also collected from those who had been diagnosed.
The study adjusted for known risk factors, such as cryptorchidism and genetic factors, in order to assess the role of diagnostic testing.
Among those with three or more exposures to diagnostic radiation, there was a 59% increase in the risk to develop TGCT compared to men with no exposure. The highest increase in risk was observed among those with at least three exposures to X-ray, including a colon X-ray, and CT below the waist.
The risk was also elevated among men exposed to diagnostic radiation during the first decade of their life.
"If our results are validated, efforts to reduce medically unnecessary and avoidable testicular exposure should be considered, in part through efforts to reduce radiation dose and optimize shielding practices when appropriate," the study authors wrote.
The study was published this month in the journal PLOS ONE.