SUNDAY, May 20, 2007 (HealthDay News) -- Exposure four decades ago to Agent Orange in the Vietnam War appears to boost veterans' risk for a recurrence of prostate cancer even after the organ is surgically removed, a new study shows.
And if the cancer does return, it tends to be more aggressive among veterans exposed to Agent Orange than in those not exposed to the chemical defoliant, the researchers found.
Black veterans are especially vulnerable to these tough-to-treat recurrences, the researchers said.
"This means that we need to make sure that these patients are not lost to follow-up, that their PSAs [prostate specific antigen levels] are checked regularly and that Vietnam veterans are screened aggressively for prostate cancer," said lead researcher Dr. Sagar Shah, a urology resident physician at the Medical College of Georgia. "The quicker that we catch [a recurrence], the more treatment options we have."
Shah's team was to present its findings Sunday at the annual meeting of the American Urological Association, in Anaheim, Calif.
Agent Orange was used to clear dense jungle cover during the Vietnam War. It contains dioxin, which, Shah said, "isn't really a tumor mutagen -- it doesn't cause cancer -- but it is a tumor-promoter. So, if the cancer is there, it makes it more prominent."
Exposure to dioxin and Agent Orange has long been linked to increased risks for a variety of malignancies, including leukemias, lymphomas, prostate cancer and lung tumors, according to Phil Kraft, program director for the National Veterans Services Fund, which lobbies on behalf of U.S. veterans.
"Agent Orange -- and its bad-guy ingredient, dioxin -- affects everyone who is exposed genetically," he said.
In the new study, Shah's team sought to determine if there were any differences in the rate or type of prostate cancer recurrences seen among a group of 1,653 black and white Vietnam veterans -- 199 of whom had been exposed to Agent Orange. All of the veterans were treated after first being diagnosed with prostate cancer between 1990 and 2006. Their treatment included surgical removal of the prostate gland.
Examination of biopsy samples under a microscope showed no pathological differences between the tumors of men exposed to Agent Orange and those who were not exposed, Shah said.
Differences did emerge, however, when the researchers compared rates of "biochemical recurrence."
Biochemical recurrence means that blood levels of the marker prostate-specific antigen -- produced by prostate cancer cells -- rose sharply and steadily in the months after surgery. Doctors routinely test men for their blood levels of PSA to help spot prostate cancer.
In this study, the shorter the time it took for a man's PSA level to double, the more aggressive his cancer appeared to be, Shah explained.
Veterans exposed to Agent Orange "had a higher relative risk of having a biochemical recurrence" than unexposed veterans, Shah said.
The rate of post-surgical prostate cancer recurrence among white veterans rose by 42 percent if they had been exposed to Agent Orange, compared to non-exposed veterans, the researchers found. Black veterans exposed to the herbicide fared even less well, with a recurrence rate that was 75 percent higher than their non-exposed peers.
And when prostate cancer did recur among veterans exposed to Agent Orange, "it seemed that they had a much shorter PSA doubling time, a surrogate for aggressiveness," Shah said.
Among black men with a cancer recurrence, PSA levels doubled in just nine months for those exposed to Agent Orange, compared to 16 months for those unexposed to the toxin.
Why might black Vietnam veterans be most vulnerable? Numerous studies conducted among the general population have already suggested that genetics or other factors put black American men at higher prostate cancer risk compared to whites.
In addition, black troops serving in Vietnam "were also more likely to have higher levels of exposure than whites," Shah noted. "They were more likely to be ground troops and less likely to be officers away from Agent Orange exposure," he said.
What does it all mean in terms of veteran's health? "When you are counseling patients on their treatment options, this is something that you can make them aware of -- that this puts you at higher risk for a recurrence," Shah said.
Shah stressed that the study did not look at recurrence rates for prostate cancer patients treated with methods other than surgery -- for example, with radiation. "We just don't know about those outcomes," he said.
"However, if he has surgery, the patient and I need to be on the same page, and I need to say, 'You have to make sure that you come in for your regular PSA test,' " Shah said. "We really have to be aware of this."
Kraft agreed that veterans' health deserves closer scrutiny, and he said that the experiences of the men and women who served in Vietnam have much to teach today's physicians and policymakers.
"We are the guys who are learning the lessons," said Kraft, himself a Vietnam veteran. "We hope we're passing that knowledge on to the Persian Gulf, Iraqi Freedom and Afghanistan veterans."
More information
Find out more about Agent Orange and its effects at the U.S. Department of Veterans Affairs.
