Scottish clues to a viral cause of leukemia.

Scottish clues to a viral cause of leukemia 

Scientists have long speculated that viruses can cause certain kinds of leukemia. Now a Scottish researcher adds new backing to the theory that childhood leukemia is caused by an infectious agent, probably a virus.

Leo Kinlen of the Cancer Epidemiology Unit at the University of Edinburgh says the increased incidence of childhood leukemia seen in several British towns may be related to their extreme geographic isolation followed by a population boom. His study, published in the Dec. 10 LANCET, postulates that clusters of childhood leukemia near Britain's Dounreay and Sellafield nuclear power plants cannot be explained by radiation exposure alone. Kinlen suggests leukemia clusters in remote areas may result from exposure to a common virus brought in by outsiders.

"It's an intriguing idea," comments Clark Heath of the American Cancer Society in Atlanta. He says a similar hypothesis was discussed during the 1960s, when U.S. scientists investigated leukemia clusters in rapidly growing suburban areas.

Both Dounreay and Sellafield reprocess nuclear fuel, and both are located in secluded areas: Dounreay at the tip of Scotland about 300 miles north of Edinburgh and Sellafield near the English Lake District. Both grew rapidly as power plant workers and their families moved there during the 1950s. Thurso, a small town 8 miles from Dounreay, saw its district population rise by 147 percent, from 3,249 in 1951 to 8,037 in 1961. The area around Seascale, a town near Sellafield, grew by 50 percent, from 1,328 to 1,990, during the same period.

To test his theory, Kinlen had to find an isolated area that had undergone a similar population boom but without a nuclear power plant. His search turned up only one town that fit the description: The New Town of Glenrothes, located in a rural region of Scotland that had undergone a 96 percent population increase during the 1950s from its base of 10,069 in 1951.

Kinlen studied death records for the area and found an excess of childhood leukemia from 1951 to 1967. "There is a significant excess of leukemia deaths below age 25 in the Glenrothes area -- 10 observed and 3.60 expected," Kinlen reports. "The finding of a significant excess of childhood leukemia in this area therefore supports tht hypothesis."

Kinlen's research findings may represent a long-awaited first step. "The ideas have been talked about for 25 years with respect to leukemia, but the evidence is hard to come by," Heath says. Kinlen agrees, saying larger studies of rural areas should be conducted. Yet the hypothesis accurately predicted an excess of leukemia in Glenrothes. "It is difficult to escape the concusion that at least some of the excesses near Dounreay and Sellafield have a similar explanation, since they represent more extreme degrees of isolation combined with population influx," he adds.

Kinlen's evidence supports the idea that childhood leukemia may be caused by a virus. But in the end, proof o that theory rests on discovery of an infectious agent. "One would hope that virologists would renew their efforts to identify a virus," Kinlen says.

Scientists already have implicated several viruses in the development of certain types of adult leukemia. The HTLV-1 retrovirus is associated with adult T-cell leukemia, a disease that is endemic in parts of Japan and the Caribbean. HTLV-2 has been linked to the T-cell variant of hairy-cell leukemia that also strikes adults.