Diagnostic radiation below the waist may increase risk for testicular cancer
Exposure to diagnostic radiation below the waist may increase risk for testicular germ cell tumors, according to results of a case-control study published in PLOS One.
If subsequent studies validate these results, efforts should be made to reduce diagnostic radiation doses to the testes, researchers wrote.
“We’ve been studying risk factors for testicular cancer for almost 20 years and have been collecting reported exposures. Kevin T. Nead, MD, MPhil, a radiation oncologist, was interested in studying how diagnostic radiation may affect risks for testicular cancer,” Katherine L. Nathanson, MD, deputy director of University of Pennsylvania's Abramson Cancer Center and Pearl Basser professor of BRCA-related research at Perelman School of Medicine at University of Pennsylvania, told Healio. “We hope to contribute to the discussion about the importance of testicular shielding for boys and men if they are getting diagnostic radiation.”
Testicular germ cell tumor is the most common form of cancer among white men aged 15 to 44 years. Incidence has doubled since 1975, from three out of 100,000 men to six out of 100,000 men, according to researchers.
The increased incidence could be linked, in part, to the 20-fold increase in the use of diagnostic radiation in the past several decades. During that time, the mean effective dose of diagnostic radiation has increased sevenfold, according to study background.
Nathanson and colleagues studied the association of diagnostic radiation exposure and testicular germ cell tumor risk among 1,246 men aged 18 to 55 years with (n = 315) and without (n = 931) testicular germ cell tumors. The men reported X-ray or CT exposure below the waist and exposure to a lower GI series or barium enema, consisting of a series of X-rays of the colon. Researchers also developed a combined measure of exposure.
The investigators used logistic regression to calculate the risk for developing testicular germ cell tumors based on number of exposures (0, 1-2 or 3) and age at first exposure. They then adjusted for age, year of birth, race, county, BMI at diagnosis, family history of the disease and personal history of cryptorchidism.
Results showed that, compared with no exposures, men who reported at least three exposures to X-ray or CT had a significantly higher risk for testicular germ cell tumors (OR = 1.78; 95% CI, 1.15-2.76), as did men who had three or more exposures to a lower GI series or barium enema (OR = 4.58; 95% CI, 2.39-8.76) or three or more exposures with the combined variable (OR = 1.59; 95% CI, 1.05-2.42).
Those exposed to diagnostic radiation at age 10 years or younger demonstrated a higher risk for testicular germ cell tumors than those first exposed at age 18 years or older, although the association was not statistically significant (OR = 2; 95% CI, 0.91-4.42).
“It is very difficult to perform a prospective study examining this question unless you have a huge number of participants,” Nathanson said. “We have a relatively small sample group, but a retrospective matched case-control study is the only option at this point in time because other study designs aren’t logistically feasible.”
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Katherine L. Nathanson, MD, can be reached at firstname.lastname@example.org.