Aging veterans exposed to Agent Orange during the Vietnam War now have more reason to worry about prostate cancer, according to a UC Davis study.
UC Davis Cancer Center physicians announced the results last week of the largest study to date that shows Agent Orange exposure is a high risk factor for developing the disease in veterans.
Agent Orange is a mixture of chemicals that contains TCDD, which is classified as a known human carcinogen, according to the American Cancer Society website. U.S. forces sprayed large quantities of the substance on Vietnam during the war to kill plants that enemies used for cover.
Research has linked the now-banned herbicide with varying extent to many different types of cancer.
“There is limited evidence so far associating [Agent Orange] with prostate cancer,” said Karim Chamie, lead author of the study, in an online briefing.
He and other physicians at the department of urology analyzed medical reports for over 13,000 veterans enrolled in the Department of Veteran Affairs Northern California Health Care System. Roughly half of the veterans were exposed to Agent Orange and the rest had no documented exposure while stationed in Vietnam during the years it was widely sprayed.
Several shortcomings in previous studies – small sample size and young age of patients – were not a factor in the current study, Chamie said. By examining a large population, the authors compared other prostate cancer risk factors between the exposed and non-exposed groups with statistical confidence. The study examined medical reports from 1998 – 2006, reflecting the tendency for the disease to develop in men later in life.
Analysis showed that twice as many veterans in the exposed group had prostate cancer, while other risk factors – race, body-mass index and smoking – did not differ significantly between the two groups. Exposed veterans were also more likely to be diagnosed with the most aggressive form of the disease and at a younger age compared to non-exposed veterans.
“Just as those with a family history of prostate cancer or who are of African American heritage are screened more frequently, so too should men with Agent Orange exposure be given priority consideration for all the screening and diagnostic tools we have at our disposal in the hopes of early detection and treatment of this disease,” said Ralph deVere White, a study co-author and UC Davis Cancer Center director, in an online briefing.
Like other high-risk groups, Vietnam veterans exposed to Agent Orange during the war are advised to screen yearly for prostate cancer, said Robert Owen, chief of environmental medicine at San Francisco VA Medical Center, who is not connected to the study. They are eligible for monetary compensation and medical treatment for the disease from VA.
“The VA has been following these veterans as high risk [for prostate cancer] for years,” Owen said. “The additional attention this study brings to the issue should be helpful in reaching veterans who are not already aware of this association and their need for active surveillance.“
The National Academy of Sciences Institute of Medicine has established a committee of experts to evaluate evidence of health effects from exposure to herbicides, including Agent Orange, and to advise the Secretary of Veteran Affairs on related policy issues. The Institute currently designates prostate cancer as having limited suggestive evidence of association with Agent Orange exposure.
“[This] study will be reviewed for the next update along with all of the other relevant information on prostate cancer that has been developed,” said David Butler, senior program officer at the National Academy of Sciences Institute of Medicine, in an e-mail interview. “The committee will weigh the strengths and weaknesses of these studies and make its determination [for the designation] based on all of the available evidence.“
The study will be published in the Sept. 15 issue of the journal Cancer.
ELAINE HSIA can be reached at campus@californiaaggie.com.
