The overall rate of cancer among children is mounting steadily, and the increase for the two most common childhood malignancies, leukemia and brain tumors, is particularly sharp, the National Cancer Institute in Bethesda says in a new report.
Researchers said that they had few clues to the reasons for the jump, and many are just now learning of the latest statistics.
But scientists emphasized that childhood cancer remained relatively rare, amounting to an estimated 7,800 new cases this year, and some suggested that at least part of the apparent increase was probably a result of better detection and reporting of the disease.
"There may be a suggestion of a trend, and there could be more cases occurring," said Dr. Leslie Robison, associate professor of pediatrics at the University of Minnesota Medical School in Minneapolis, who is participating in a study of leukemia in children. "But the numbers are still small, and it's possible that some of them are due to better diagnosis and collection of case information."
Some scientists say another potential risk factor may be electromagnetic radiation such as that emitted by television sets, toaster ovens and other common household devices. Researchers continue to quarrel over the link between electricity and cancer, but even skeptics admit that they cannot dismiss a connection out of hand, and studies of electromagnetism as a possible cancer risk factor are proceeding.
According to a report released this week by the National Cancer Institute, the rate of cancer among white U.S. children up to 14 years old increased more than 4.1 percent from 1973 to 1988.
For the most common childhood malignancy, acute lymphocytic leukemia, the rate of increase over the 15-year period was 10.7 percent, and for brain tumors, the second most prevalent cancer among the young, the incidence soared by 30.5 percent.
As stark as those figures sound, scientists stressed that the numbers of cases involved were small. In the case of leukemia, the rate rose to 3.2 cases for every 100,000 children in 1988 from 2.4 cases per 100,000 children in 1973.
For brain cancer, the figure increased to a rate of 3.4 cases for every 100,000 children in 1988 from 2.3 cases per 100,000 children 15 years earlier.
"I'm not going to use the word 'disturbing,' because that's too strong," said Lynn A. Ries, a health statistician at the cancer institute who helped compile the new figures. "But the numbers are statistically significant, and now it's up to others to determine what, if anything, may explain them."
The latest figures on childhood cancer are part of the institute's annual review of cancer trends in the United States. The statistics are calculated from data gathered at hospitals and registries throughout the nation that cover about 10 percent of the population.