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NEW YORK (Reuters Health) - Children born with birth defects or to mothers with a history of multiple stillbirths may have a higher-than-normal risk of brain cancer, a new study suggests.
The risks are still small, researchers say, as children only rarely develop brain cancer. Each year, about 4,000 U.S. children and teenagers are diagnosed with a tumor of the central nervous system (brain or spinal cord), according to the American Cancer Society.
A small portion are caused by specific, inherited genetic syndromes, but otherwise little is known about why children develop brain and spinal cancers.
The new findings, published in the journal Pediatrics, highlight the potential importance of genetic factors, the researchers say.
Using a California database on cancer cases in the state, the researchers found 3,733 cases of brain or spinal tumors diagnosed among children younger than 15 between 1988 and 2006.
Overall, 1.2 percent of those children had been born with a birth defect -- versus 0.6 percent of 15,000 cancer-free California children studied for comparison.
And children with a birth defect had increased risks of certain tumors.
They were nearly four times as likely as children without birth defects to develop a primitive neuroectodermal tumor -- tumors that start in immature cells of the brain, and account for about one-fifth of childhood brain tumors.
Similarly, their risk of germ cell tumors, a rare form of brain tumor in children, was elevated more than six-fold.
Children with birth defects were not, however, at higher risk for the most common type of brain cancer in the study group -- gliomas, which accounted for 57 percent of cases.
The study also found heightened tumor risks among children whose mothers had had at least two late pregnancy losses in the past -- meaning the fetus died after the 20th week of pregnancy, commonly known as a stillbirth.
These children were about three times as likely as other kids to develop some type of brain or spinal tumor.
Since both birth defects and pregnancy losses often involve some type of genetic abnormality, it's possible that that explains the higher cancer risks, according to the researchers.
"Genetics may play a larger role in central nervous system cancer than previously believed," said lead researcher Dr. Sonia Partap, of Stanford University and Lucile Packard Children's Hospital in Palo Alto, California.
Miscarriages were not linked to cancer risks in a woman's other children. So it's possible that the genetic abnormalities that cause early pregnancy loss are not connected to cancer, while gene defects that are "compatible with life to some degree" do contribute to cancer risk, Partap told Reuters Health in an email.
As for birth defects, past studies have connected them to higher risks of childhood cancers in general.
But researchers are still trying to figure out whether it's only certain birth defects that come with a higher risk. Some preliminary evidence, Partap said, suggests that defects of the heart and brain may be particularly linked to childhood cancer.
But Partap also stressed that even with a relatively increased risk of brain or spinal cancer, the absolute risk to any one child is small.
"Parents should know that there is still a very low risk of central nervous system cancer," Partap said.
At the same time, she added, pediatricians should be aware that there is a slightly higher chance of the tumors in certain children.
Symptoms of brain tumors may be vague and vary from child to child. But some possible signs include morning headaches; mental changes like memory and concentration problems; unusual sleepiness; changes in vision, hearing or speech; and balance or coordination problems.
SOURCE: bit.ly/oWBZpY Pediatrics, online August 8, 2011.