Even low doses of radiation therapy posed a risk for survivors of a childhood cancer — something not known before, according to study results presented Monday in Chicago at the annual meeting of the American Society of Clinical Oncology.That means more women might need to be screened beginning at age 25 for breast cancer.
“We find that by age 50, approximately 30 percent of women treated with radiation for Hodgkin lymphoma” as girls have developed breast cancer, said Chaya Moskowitz, a biostatistician at Memorial Sloan-Kettering Cancer Center in New York, who led the federally funded study.
That’s far higher than the 4 percent rate for the general population and comparable to the rate in women who have mutations in inherited BRCA genes that increase risk. Among women who had chest radiation for any type of childhood cancer, 24 percent developed breast cancer by age 50.
Nearly 60,000 American women alive today had chest radiation for any pediatric cancer, the study found.
Radiation treatment has saved countless children from lymphoma, leukemia, soft-tissue tumors and other cancer types, but it can damage the DNA of healthy cells, too, and lead to cancer decades later.Children treated today get much lower doses and to much smaller areas of the body than kids did in 1970 to 1986 when the women in this study were girls.
Before the 1970s, few children with cancer even survived. Yet the research reflects a growing sensitivity that “cure is not enough,” says Dr. Michael Link, outgoing president of the oncology society.
As these survivors have grown up and hit middle age, doctors are finding a substantially increased risk of breast cancer, even among girls who received what was considered to be a “lower” dose of radiation, Moskowitz says.
“We need to know how to take care of survivors and change childhood cancer therapies, so this doesn’t happen to the next group of survivors,” says Lisa Diller of Boston’s Dana-Farber Cancer Institute. “Children treated for Hodgkin lymphoma today are treated with therapies that try to maintain the excellent cure rates but use as little radiation as possible.”
The Children’s Oncology Group recommends women treated with higher doses of radiation begin breast-cancer screenings at age 25, or eight years after finishing radiation, whichever comes later, using both mammograms and MRI, or magnetic resonance imaging. Typically, medical societies recommend women at normal risk for breast cancer begin getting screening at age 40 or 50.
Moskowitz says doctors might need to re-evaluate those guidelines for pediatric cancer survivors.