Prostate cancer is the second most commonly diagnosed cancer in men, and it will affect one in six men at some point during their lives. Fortunately, the vast majority of prostate cancers are considered low grade and thus pose no serious threat. That’s why the US Preventive Services Task Force recommends against routine prostate cancer screening—because such screening can lead to more tests and treatments that needlessly cause pain, incontinence and erectile dysfunction in men whose slow-growing prostate cancers are unlikely to ever pose a threat.

However: Prostate cancer screening is very important for a certain group of men—those who served in the Vietnam War in areas where the herbicide Agent Orange was used.

During that war, millions of gallons of Agent Orange were sprayed in forests and on mangroves to remove the enemy’s protective cover of vegetation. Exposure to the toxic dioxins in Agent Orange has been linked to increased risk for many diseases, including type 2 diabetes, Parkinson’s disease, Hodgkin’s disease—and prostate cancer.

What the researchers in a new study wanted to determine was whether Vietnam veterans exposed to Agent Orange were particularly at risk of developing aggressive, potentially lethal, high-grade prostate cancers. To find out, they studied 2,720 men undergoing prostate biopsies at one Veterans Administration medical center who did not have a history of prostate cancer or a previous prostate biopsy.

When prostate cancer was found, pathologists determined each patient’s Gleason score (a number from two to 10 that reflects the severity of the tumor, with higher numbers being more severe). Then the researchers linked that score to a database of veterans’ information so that other risk factors—including exposure to Agent Orange—could be analyzed for each patient. Veterans were considered to have been exposed to the herbicide if they had served in a location where Agent Orange was known to have been used.

Study findings: Veterans who were exposed to Agent Orange had a 52% greater risk than unexposed veterans of being diagnosed with prostate cancer. When researchers considered only high-grade cancers (a Gleason score of at least seven), the exposed vets’ risk was 75% greater…when considering those with Gleason scores of eight or higher, the exposed vets’ risk was more than double that of the unexposed veterans. What’s more, the men exposed to Agent Orange were, on average, nearly five years younger (61.4 years) when they had their prostate biopsies, compared with unexposed veterans (66.1 years)—indicating that not only were exposed vets more likely to get advanced prostate cancer, they developed it earlier, too.

Vietnam vets: Speak to your doctor about being screened for prostate cancer. If there’s a chance that you were exposed to Agent Orange, the general guidelines against routine screening do not apply to you. Screening could lead to earlier detection and treatment of prostate cancer, potentially prolonging your life. And of course, any man with possible symptoms of prostate cancer—trouble urinating, decreased force in the urine stream, blood in the urine or semen—should be tested as well.