Vietnam War veterans exposed to Agent Orange may have greatly increased risks of getting the most aggressive form of prostate cancer, according to US scientists. Agent Orange is a powerful herbicide that was used to destroy dense forests to better visualize enemy activity.

UC Davis Cancer Center physicians involved a large population of men in their 60s, and the prostate-specific antigen (PSA) test to screen for the disease in their study, which they claim is the first to link the herbicide with this form of cancer.

"While others have linked Agent Orange to cancers such as soft-tissue sarcomas, Hodgkin's disease and non-Hodgkin's lymphoma, there is limited evidence so far associating it with prostate cancer," said Karim Chamie, lead author of the study and resident physician with the UC Davis Department of Urology and the VA Northern California Health Care System.

"Here we report on the largest study to date of Vietnam War veterans exposed to Agent Orange and the incidence of prostate cancer," the researcher added.

During the study, the researchers stratified over 13,000 Vietnam veterans enrolled in the VA Northern California Health Care System into two groups - exposed or not exposed to Agent Orange between 1962 and 1971.

Based on medical evaluations conducted between 1998 and 2006, the study revealed that twice as many men exposed to Agent Orange were identified with prostate cancer.

Furthermore, Agent Orange-exposed men were diagnosed two-and-a-half years younger, and were nearly four times more likely to present with metastatic disease.