Researchers have found that men exposed to Agent Orange chemicals during the Vietnam War carry a higher risk for developing life-threatening prostate cancer than those who were not exposed to the chemicals.

Additionally, they found that those exposed to the chemicals were diagnosed with cancer on average around five years earlier than those who were not.

"This is a very, very strong predictor of lethal cancer," urologist Dr. Mark Garzotto, MD, of the Portland Veterans Administration Medical Center and Oregon Health & Science University, said. "If you're a person who's otherwise healthy and you've been exposed to Agent Orange, that has important implications for whether you should be screened or not screened."

During the Vietnam War, the U.S. military used the Agent Orange chemicals to destroy foliage, mostly in southern Vietnam. It often contained a type of dioxin and was named after the giant orange drums in which the substance was contained.

In coming to their conclusion, the researchers examined the medical records of 2,720 veterans referred for a prostate biopsy to the Portland VA. According to interviews, around one in 13 had been exposed to Agent Orange. One third of the men were diagnosed with prostate cancer and the researchers found that those exposed to Agent Orange were 52 percent more likely to contract the cancer.

While the chemicals were not linked to low-grade cancer, they were associated with a 75 percent higher chance of developing aggressive prostate cancer.

If the study is accurate, then determination of Agent Orange exposure could lead to improved prostate cancer screenings for U.S. veterans.

"It also should raise awareness about potential harms of chemical contaminants in biologic agents used in warfare and the risks associated with waste handling and other chemical processes that generate dioxin or dioxin-related compounds," Garzotto said.

The study is published Monday May 13 in the American Cancer Society's journal Cancer.