Veterans exposed to Agent Orange have a 48 percent increased risk of prostate cancer recurrence following surgery than their unexposed peers, and when the disease comes back, it seems more aggressive, researchers say.
"We need to be screening these patients earlier, treating their cancer aggressively and following them closely afterward because they are at higher risk for recurrence," says Dr. Martha Terris, chief of the Urology Department at the Augusta Veterans Affairs Medical Center and professor of urology at the Medical College of Georgia.
"We looked at all patients, whether they were exposed or not, to see which were more likely to develop a recurrence and patients with a history of Agent Orange exposure were more likely," says Dr. Sagar R. Shah, MCG urology resident who is presenting the data May 20 during the American Urological Association Annual Meeting in Anaheim, Calif.
The study looked at 1,653 veterans who had prostate cancer surgery at Department of Veterans Affairs Medical Centers in five cities between 1990 and 2006; 199 had been exposed to Agent Orange, a herbicide and defoliant sprayed on the dense forests of Vietnam during the war.
Agent Orange contains the carcinogen, dioxin, which can be stored in body fat and is believed to make its way into the cell nucleus and work as a tumor promoter. In the past, relatively higher mortality rates have been found in chemical plant workers and farmers with prostate cancer who were exposed to dioxin, the researchers write in their abstract.
Dioxin's impact is dose-related, and while the researchers did not measure levels of dioxin or Agent Orange, they suspect that blacks, who were more likely to be ground troops, also were more likely to have had more Agent Orange exposure.
Researchers found veterans with Agent Orange exposure more likely to be black and younger at the time of surgery to remove their prostate gland. The disease appeared to be caught earlier in exposed veterans. Most had their disease staged as T1 by pathologists, which means it appeared confined to the prostate gland, and had lower pre-operative prostate specific antigen scores, an indicator of disease aggressiveness.
However, when the disease recurred, exposed veterans experienced a more rapid biochemical progression of their disease, which PSA measures. In blacks, the PSA doubled in almost half the time of their unexposed peers.
A blood PSA level screens for prostate cancer for most men beginning at age 50 and at age 40 for blacks and men with a family history. Black men have been shown by Dr. Terris and others to have more aggressive disease earlier in life.
To account for known racial differences, researchers also compared recurrence rates in exposed and non-exposed blacks and whites and the results held up.
"As a population in general, if you were exposed to Agent Orange, you're more likely to have a recurrence," says Dr. Shah. "If you were black and exposed, you were more likely to recur than if you were black and unexposed."
If it sounds odd that men who had their prostate removed could have disease recurrence, Dr. Terris points out that microscopic cancer cells can migrate out of the area before surgery, becoming detectable later when they start pushing PSA levels back up.
In fact, following any type of prostate cancer treatment, men routinely get PSA levels checked for the rest of their lives. Without cancer recurrence, they should stay at zero.
The study was funded by the Georgia Cancer Coalition and the Department of Veterans Affairs.