STORIES

Should FL believe new map?

By Cynthia Washam
3/4/2010 © Health News Florida
A new study by a team of North Florida researchers that suggests an elevated risk of pediatric cancer in two large swaths of Florida is drawing skepticism from many epidemiologists.

One of the two zones, which takes up most of the lower third of the state, has a risk 52 percent higher than that in most of the state, the researchers said. A risk zone in the north of the state is somewhat weaker, they said.

“We’re very concerned about what’s going on in our state,” said co-author Chatchawin Assanasen, pediatric hematologist/oncologist with the Nemours Center for Childhood Cancer Research in Pensacola. “Clusters of this size are unusual.”

The results, which appeared Jan. 6 in the online version of the medical journal Pediatric Blood & Cancer, are just too unusual to give many epidemiologists confidence in them.

One who tried to replicate the study and couldn’t is epidemiologist Jill MacKinnon, director of the Florida Cancer Data System at the University of Miami. Her program has a contract with the Department of Health (DOH) to collect data on all cancer cases in Florida.

The cancer data Assanasen and his Nemours colleagues used were incomplete, she said; when she plugged in data from her office, the massive clusters disappeared.

The only cluster she found was a small one in western Palm Beach County.

Epidemiologist Dana Rollison of Moffitt Cancer Center in Tampa also had doubts about the new study, saying the researchers used outdated 2000 census data.

The state agency charged with investigating cancer clusters dismissed the Nemours study.

“I don’t think the Department of Health feels we should move forward based on this one study,” said senior environmental epidemiologist Sharon Watkins. “We look at findings to be validated and replicated.”

Assanasen, meanwhile, is spreading the news of Florida’s massive childhood cancer clusters in consumer and medical media. He discussed his study at a medical meeting in Texas shortly after it was published and is scheduled to do so again at an April meeting in Montreal.

“Our article was (reviewed by other scientists) and published,” he said. “We welcome anyone to discuss the findings with us.”

Cancer rates still low in cluster

The Nemours researchers examined childhood cancer rates by counting cancer cases in each Florida zip code. The South Florida cluster they found roughly spans from Port Charlotte east to Okeechobee, and south to Homestead. It encompasses everything from waterfront mansions to ramshackle migrant housing, but stops just west of the densely populated strip of cities along the east coast.

“It appears the heavily populated areas of Miami, Fort Lauderdale, are somewhat protected,” Assanasen said.

The second, weaker cluster stretches from Ocala north to the Georgia border.

Assanasen doesn’t identify the cities at the fringes of the boundaries.

“We tried to keep ZIP code blind for privacy issues,” he said.

The Nemours researchers got their data on childhood cancers from the Florida Association of Pediatric Tumor Programs (FAPTP) at the University of South Florida. The FAPTP collects information on pediatric cancer cases from Florida hospitals, much like the Miami-based Florida Cancer Data System.

The FAPTP database is only about 80 percent complete, said Miami’s MacKinnon, which led Assanasen and his colleagues to overestimate the cancer rate in South Florida.

Moffitt epidemiologist Rollison sees little reason for concern, even if the Nemours data are accurate.

“There’s always a chance you’ll find things higher than you’d expect,” she said. An elevated risk of 52 percent is not that strong an association, Rollison said, considering how few children have cancer.

Assanasen’s study showed that in 2007, the overall childhood cancer rate in Florida was nearly 16 per 100,000. In the South Florida cluster, the rate was just under 22.

Cause tough to pinpoint

With their study showing childhood cancers concentrated in South Florida, the Nemours researchers naturally thought of an environmental link.

“We suspect (drinking) water may be involved,” Assanasen said, but added, “We have no strict conclusions. It requires further study to tease things out.”

Private wells, which are not regulated, might be contaminated by pesticides and other chemicals dispersed through South Florida’s shallow aquifer, he said. The major cities that escaped the cluster are served by municipal water supplies that must meet federal standards.

But it’s one thing to find an elevated risk and another to determine the reason.

“Most clusters that are identified and verified are never attributed to a cause,” Rollison said. “The challenge, particularly in Florida, is mobility. Children are diagnosed at a certain age. But cancer takes years to develop, particularly if it’s from an environmental exposure.”

State and federal investigators have been working for several months to find out why 13 children in West Palm Beach’s Acreage community developed brain tumors or cancer in recent years. Although some parents suspect contaminated water, health officials have found no clear link.

Rollison says she’d like to see the Nemours study repeated when there is a more up-to-date count of Florida’s children.

“They should go back,” she said, “and do it with 2010 census data.”

--Independent journalist Cynthia Washam of Jensen Beach can be reached by e-mail.