AGENT ORANGE & PROSTATE CANCER
Agent Orange is a liquid defoliant that was extensively used during the Vietnam War. During the War, an estimated 19 million gallons of herbicides were sprayed over heavily forested areas of Vietnam and Laos, the majority of which consisted of Agent Orange. (The term “Agent Orange” came about due to the orange stripe that was used to mark drums containing 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid.)
The areas around American bases were often targeted for defoliation, in an effort improve security. Additionally, many of the areas where American troops, and their allies, operated also received heavy aerial applications of Agent Orange as well. Millions of Vietnamese were also exposed to Agent Orange, and not only for the duration of the War, but throughout the decades that followed the final exodus of the American forces.
Agent Orange contains chemical contaminants known as dioxins, which are organic chemicals that tend to persist in the environment, and within exposed humans and animals, for many years. Because of this property, dioxins are often referred to as “persistent organic pollutants.” Following the publication of a research paper, in 1970, that linked Agent Orange with birth defects in laboratory animals, the use of chemical defoliants was discontinued by American forces in Vietnam during the War. By this time, however, as many as 1.5 million American soldiers, and nearly 5 million Vietnamese, had already been exposed to Agent Orange.
Many American soldiers who were heavily exposed to Agent Orange returned from Vietnam complaining of persistent skin rashes, cancers of the blood and lymph nodes (leukemia and lymphoma), psychiatric illnesses, and birth defects in their children. However, despite a successful class action lawsuit that was brought by exposed veterans in 1979, and settled in 1984, there remains a great deal of controversy regarding the short-term and long-term health effects of exposure to Agent Orange. Unfortunately, although multiple research studies have been published on the subject of Agent Orange’s potential adverse health effects, these studies have often reached contradictory conclusions.
A new research study, just published in the journal Cancer, raises concerns that Agent Orange exposure might be linked to an increased risk of prostate cancer among Vietnam War veterans who were exposed to the herbicide during the War. This study was performed by researchers at the University of California at Davis and the Veterans Administration (VA) Northern California Health Care System.
Using the VA’s clinical database, more than 13,000 veterans of the Vietnam War were assessed. Approximately 6,200 of these vets were identified as having been exposed to Agent Orange during the War, while another 6,900 veterans were considered to have been “unexposed.” Using this large clinical database, the incidence of prostate cancer in both groups of male veterans was determined. Additional important risk factors for prostate cancer were also evaluated in these 13,000 men, including age, race, smoking history, family history of cancer, presence or absence of obesity, prostate-specific antigen (PSA) levels, and prior use of finasteride (a medication used to treat enlargement of the prostate gland, and which has also been shown to decrease the risk of developing prostate cancer).
When the researchers analyzed the two groups of male veterans, they found that prostate cancer was more than twice as common among the men who had been exposed to Agent Orange during the Vietnam War. Not only was prostate cancer more common among the men who had been exposed to Agent Orange, but their prostate cancers appeared to occur at an earlier age (the average age at diagnosis was 60 years among the exposed veterans and 62 years for the unexposed vets). Moreover, the microscopic appearance, or grade, of the prostate cancers that developed in the exposed men was much more worrisome (i.e., higher grade) when compared to the cancers that occurred in the unexposed men. Finally, the exposed veterans who developed prostate cancer were more than 3 times as likely to already have spread of their cancer outside of the prostate gland at the time of diagnosis when compared to the men the men who had not been exposed to Agent Orange. When the researchers evaluated all of the other known risks factors for prostate cancer present in these two groups of men, only their Agent Orange exposure history seemed to explain the striking differences in the incidence and severity of prostate cancers that were observed in this research study.
While this was a retrospective study, which increases the risk of introducing bias into the results and conclusions of such studies, the results are nevertheless quite striking, especially in view of the fact that the researchers eliminated the most common risk factors for prostate cancer as potential explanations for the differences observed between the two groups of veterans. In summary, the group of veterans who were exposed to Agent Orange during the War, when compared to their comrades who were not exposed to this herbicide, experienced a greater incidence of prostate cancer, an earlier age of prostate cancer onset, and more aggressive forms of this disease.
The authors of this study suggest, based upon their findings, that a prior history of exposure to Agent Orange (or to dioxins) should now be considered a significant risk factor for prostate cancer, which seems reasonable based upon the results of this research study. This potential new risk factor joins the already well established risk factors of increasing age, African-American race, a family history of prostate cancer and obesity. If you believe that you may have been previously exposed to Agent Orange, or to other sources of dioxins, then you should notify your physician. Based upon the results of this study, if you have a history of significant exposure to these chemicals, then your physician should follow you carefully for any signs or symptoms of early prostate cancer, especially if you are approaching the age of 60, or you are already older than 60. Routine digital rectal examinations and measurements of the level of PSA in your blood should be performed on at least an annual basis.
Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity.
Dr. Wascher is an oncologic surgeon, professor of surgery, a widely published author, and the Director of the Division of Surgical Oncology at Newark Beth Israel Medical Center
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Copyright 2008. Robert A. Wascher, MD, FACS. All rights reserved.
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