FALLON, Nev. -- Children in a Northern Nevada leukemia cluster are more likely to have a variation in a gene that helps combat unsafe chemicals, and more research is needed to learn why, federal researchers said yesterday.
The study released by the Centers for Disease Control and Prevention is the latest to suggest genetics and toxins play a role in the cancer cluster plaguing the agricultural community.
Since 1997, 17 children with ties to Fallon have been diagnosed with acute lymphocytic leukemia, and three have died. Health officials say about one leukemia case in five years would be expected.
"All we can say is we saw a difference, but we don't know what that means yet. The significance is that researchers need to investigate this," said Dr. Karen Steinberg, chief science officer of the CDC's Coordinating Center for Health Promotion.
The gene variation "might mean that it alters susceptibility [to leukemia] but it doesn't cause leukemia," she said at a media briefing Wednesday. There would have to be other factors to affect susceptibility, she added.
An earlier study headed by the CDC failed to find an environmental cause for the cluster. It reported that Fallon-area residents had higher levels of tungsten and arsenic in their blood and urine but that there was no evidence the substances caused leukemia.
The latest DNA study found that all 11 children with leukemia who were tested had a variation in the SUOX gene, which tells the body how to make sulfite oxidase. Sulfite oxidase is an enzyme that normally helps convert sulfites to sulfate for excretion. Lack of this enzyme because of a genetic defect can cause neurological problems and early death.
By comparison, 10 of 24 healthy Fallon-area children who were tested had the gene variation. Sulfite oxidase changes an unsafe chemical into a safer one.
CDC officials said that even if the variation in the SUOX gene adds to the risk for leukemia, other factors must be involved. Researchers have not identified those factors or the cause of the Fallon cluster, they said.
Scientists must determine the effect of variations in the SUOX gene and whether the variation changes the likelihood that a child will get leukemia, they added.
"The genetics test took it [the research] to the next logical level, and what we have to do is build on it," said Dr. Carol Rubin, chief of the CDC's health studies branch.
The call for more research was praised by the incoming Senate majority leader, Harry Reid, Democrat of Nevada. "While the exact cause of the cancer cluster is still unknown, I remain committed to finding answers," he said.