MONDAY, Dec. 12 (HealthDay News) -- Children of parents who survived childhood cancer are unlikely to suffer from birth defects, finds a new study that should allay some concerns about long-term effects of treatment.

It appears that DNA damage done by chemotherapy and radiation of the reproductive organs doesn't increase the risk that children will inherit those damaged genes, researchers say.

"We found that DNA damage from radiation and chemotherapy with alkylating agents are not associated with the risk of genetic birth defects in the offspring," said lead researcher Lisa Signorello, an associate professor of medicine at Vanderbilt University in Nashville.

"This is really reassuring," she said. "This is one less thing for childhood cancer survivors to worry about." The prevalence of birth defects among the children of cancer survivors is similar to that of the general population, added Signorello, who's also a senior epidemiologist at the International Epidemiology Institute in Rockville, Md.

While life-saving in many cases, radiotherapy and chemotherapy with alkylating agents, such as busulfan, cyclophosphamide and dacarbazine, can damage DNA.

Signorello noted that childhood cancer survivors have a higher rate of infertility and a greater risk of having miscarriage, preterm birth and low birth-weight infants.

Although cancer treatment can cause DNA damage to the sperm and eggs, "it may be that these damages get filtered out," she said.

Genetic-based birth defects are rare, accounting for about 3 percent of births. Although earlier research found little or no increased risk for birth defects among the children of cancer survivors, the studies were small in size and lacked detailed data about radiation and chemotherapy, such as radiation doses to the testes and ovaries, the researchers noted.

The report was published in the Dec. 12 issue of the Journal of Clinical Oncology.

For the study, Signorello and colleagues collected data on more than 20,000 children who had survived cancer. The data were taken from the 1970 and 1986 Childhood Cancer Survivor Study. Fifty-seven percent of them had been treated for leukemia or lymphoma.

The researchers also looked at the health of nearly 4,700 children of these survivors.

Of the parents treated for cancer, 63 percent had radiation therapy and 44 percent of men and 50 percent of women had chemotherapy.

Among their children, 2.7 percent had at least one birth defect such as Down syndrome, achondroplasia (dwarfism), or cleft lip.

Three percent of the mothers exposed to radiation or treated with alkylating chemotherapy had a child with a genetic birth defect, compared with 3.5 percent of mothers who survived cancer, but weren't exposed to these treatments, the researchers found.

Only 1.9 percent of children of the cancer-surviving fathers had these birth defects, compared with 1.7 percent of children of fathers who did not have chemotherapy or radiation, they said.

"This is very encouraging, because there has been a worry," said Dr. Michael Katz, senior vice president for research and global programs at the March of Dimes.

Dr. Jeanette Falck Winther, a senior researcher at the Institute of Cancer Epidemiology at the Danish Cancer Society in Copenhagen and co-author of an accompanying journal editorial, said the study findings should address some of the reproductive concerns of childhood cancer survivors, geneticists and pediatric oncologists.

"Our hope is that this reassuring information will be used by the physicians in counseling childhood cancer survivors who desire and are able to have children," she said.

More information

For more information on childhood cancer, visit the American Cancer Society.