PCa Recurrence, Agent Orange Linked
ANAHEIM, Calif.—Among black Vietnam veterans with prostate cancer, those who had been exposed to Agent Orange are at significantly increased risk of cancer recurrence following surgery, according to a study.
“We suggest earlier screening of African Americans with Agent Orange exposure, treating their cancer aggressively and following them closely due to the potential higher risk for recurrence,” said study investigator Martha Terris, MD, chief of urology at the Augusta (Ga.) Veterans Affairs Medical Center and professor of urology at the Medical College of Georgia in Augusta.
She and her colleagues studied 1,653 veterans who had prostate cancer surgery at the VA medical centers in five cities between 1990 and 2006. Among these men, 199 had a history of exposure to Agent Orange, an herbicide and defoliant sprayed on the dense forests of Vietnam during the war, and 1,454 were not exposed. The exposed and unexposed men had a mean age 58.4 and 62.4 years, respectively. A total of 532 men (33%) experienced biochemical progression, defined at a PSA level greater than 0.2 ng/mL, two consecutive PSA measurements of 0.2 ng/mL, or secondary treatment for an elevated postoperative PSA.
Exposed veterans were more likely to be black and younger at the time of surgery to remove the prostate, Dr. Terris' group found. Most had their disease staged as T1 and had lower preoperative PSA scores.
Among black men, Agent Orange exposure was associated with a significant 75% increased likelihood of biochemical recurrence after adjustment for multiple clinical characteristics. Exposure also was associated with a shorter mean adjusted PSA doubling time at the time of recurrence (9.1 vs. 16 months). The researchers observed no significant association between Agent Orange exposure and prostate cancer recurrence or PSADT at the time of recurrence in non-black men.
Agent Orange contains dioxin, a carcinogen that can be stored in body fat and is believed to make its way into the cell nucleus and work as a tumor promoter. Relatively higher mortality rates have been found in chemical plant workers and farmers with prostate cancer who were exposed to dioxin, Dr. Terris said. Dioxin's impact is dose-related. Although the researchers did not measure levels of dioxin or Agent Orange, they suspect that blacks, who are more likely to be ground troops, also were more likely to have had greater exposure to Agent Orange.
“To our knowledge, this is the first study to actually compare recurrence rates to Agent Orange exposure,” Dr. Terris told Renal & Urology News. “The jury is still out on how this will impact the care of these patients. Vietnam veterans are just now entering the age where most of them are at risk for prostate cancer. We certainly need to screen those patients diligently and be sure to monitor them carefully for recurrence after treatment.”
Findings were reported here at the American Urological Association annual meeting.