A new study of US Veterans has found that exposure to Agent Orange is linked to a two-fold higher risk of developing the most lethal forms of prostate cancer. The researchers suggest a history of exposure to the agent, which contains the dioxin TCDD, a dangerous toxin and carcinogen, should be one of the first things to look for when screening Veterans as it could lead to earlier diagnosis and treatment and prolong survival.
Previous studies have already established a link between exposure to Agent Orange, a herbicide and defoliant that was heavily used as a chemical weapon in the era of the Vietnam War, but they did not clarify whether the link was specifically to the lethal forms of the disease.
In this latest study, expected to be published in the journal Cancer on 13 May, principal investigator Mark Garzotto of the Portland Veterans Administration Medical Center and Oregon Health and Science University, and colleagues found exposure to Agent Orange was not linked to an increased risk of low-grade prostate cancer, but was linked to an increased risk of high-grade prostate cancer.
In a statement to the press, Garzotto says the distinction is important because most cases of prostate cancer are non-lethal and so do not necessarily require detection or therapy.
“Having a means of specifically detecting life-threatening cancer would improve the effectiveness of screening and treatment of prostate cancer,” he adds.
For their study, the researchers analyzed clinical information and biopsy results from 2,720 US Veterans who had been referred by several different care providers for initial prostate biopsy.
The biopsy results showed that 896 of the Veterans (33%) were diagnosed with prostate cancer, 459 of them (17% of the total) with high-grade disease.
Analysis revealed that a history of exposure to Agent Orange was tied to a 52% overall risk of a biopsy showing presence of any grade of prostate cancer, a 75% raised risk of high-grade prostate cancer, and a two-fold raised risk of the highest grade, most lethal forms.
However, exposure to the herbicide was not linked to an increased risk of low-grade prostate cancer.
The researchers say their findings show knowing whether they have been exposed to Agent Orange is a readily identifiable way to improve prostate cancer screening for Veterans. Lethal cases would be spotted earlier, which with prompt treatment could potentially prolong survival and improve quality of life for patients.
Garzotto says he also hopes the study will make people more aware of the health harms of chemical agents used in warfare, and of the risks posed by dioxin or dioxin-related compounds in other chemical processes like waste handling.
The study did not investigate the mechanisms through which TCCD may increase the risk of lethal prostate cancer.
In 2007, a team from the University of Pennsylvania School of Veterinary Medicine reported a study where they found dioxin attacks mitochondria, the cellular machinery that converts oxygen and nutrients into cellular fuel, disrupting normal cell function and eventually promoting tumor progression.
TCCD (2,3,7,8-tetrachlorodibenzo-p-dioxin) was the dioxin used to poison Ukrainian President Victor Yushchenko in 2004.
Written by Catharine Paddock PhD