SATURDAY, May 14 (HealthDay News) -- There appears to be a link between Agent Orange and kidney cancer in U.S. veterans exposed to the herbicide in Vietnam, a new study suggests.

Researchers at the Veterans Affairs Medical Center in Shreveport, La. examined the records of 297 patients diagnosed with kidney cancer between 1987 and 2009. Thirteen of the patients, aged 39 to 63 when they were diagnosed, said they had been exposed to Agent Orange.

Documented exposure to the herbicide and pathology reports were available for 10 of the patients. The researchers reviewed these patients' age at diagnosis, tumor size, side of lesion, pathology and survival.

Nine of the 10 patients had clear-cell cancers, which typically have worse outcomes than papillary tumors, which appeared in one patient. One patient had both clear-cell and papillary cancers.

During the average follow-up of 54 months, four patients developed metastatic cancer and one patient died from his cancer.

The findings were presented Saturday during a special news conference at the American Urological Association (AUA) annual meeting in Washington, D.C. Research presented at meetings should be viewed as preliminary because it has not been subjected to the peer review that typically accompanies publication in a medical journal.

"We know that the chemicals in Agent Orange were extremely toxic, and are known to cause cancer," press conference moderator Dr. Anthony Y. Smith said in an AUA news release. "These data indicate that we may need to better determine whether exposure to these chemicals should be considered a risk factor for kidney cancer."

More information

The U.S. Department of Veterans Affairs has more about Agent Orange.