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WASHINGTON (Reuters) - Women who underwent chest radiation as part of treatment for childhood cancer often are not getting recommended breast cancer screenings despite being at high risk for the disease, researchers said on Tuesday.
Their study involved women in the United States and Canada who had cancers such as Hodgkin's disease as children or young adults and were treated with moderate- to high-dose radiation to the chest, which can raise the risk of breast cancer.
Experts recommend these women have an annual mammogram, or breast X-ray, to screen for breast cancer starting at age 25, or eight years after radiation treatment, whichever is later.
But among women ages 25 to 39 in this group, 47 percent had never had a mammogram, and only 23 percent had undergone one in the past year, the researchers wrote in the Journal of the American Medical Association.
"The rates were quite low, lower than what we anticipated," said Dr. Kevin Oeffinger of Memorial Sloan-Kettering Cancer Center in New York, who led the study.
By age 45, up to 20 percent of these women get breast cancer, many of them in their 30s, he said.
"It's not a question of the women avoiding screening," Oeffinger said in a telephone interview. "It's a lack of them understanding their risk and physicians being unfamiliar with the risk in this population, especially for the younger patients."
The study tracked 625 women ages 25 to 50 who had chest radiation when they were young to treat cancer.
About 70 percent had been treated for Hodgkin's disease, a cancer of the lymphatic system. Others survived non-Hodgkin's lymphoma, a kidney cancer called Wilms' tumor, the nerve cell cancer neuroblastoma and others.
Mammograms are important in spotting breast cancer at an early stage when it is most treatable. The American Cancer Society recommends women start getting annual mammograms at age 40, so doctors do not usually discuss it with younger women.
Oeffinger played down the potential harm from the radiation doses in annual mammograms for these women.
The reason they have a high breast cancer risk is the whopping dose of radiation they got in their childhood cancer treatment, and a lifetime of mammograms would amount to less than 1 percent of that earlier radiation exposure, he said.
A second study published on Tuesday in the Journal of the National Cancer Institute looked at early mammograms in another group of young women at high risk for breast cancer -- those under age 30 who have a mutation in the genes BRCA1 or BRCA2.
Women with these mutations are encouraged to start mammograms annually at age 25 to 30.
Amy Berrington de Gonzalez of Johns Hopkins University in Baltimore and colleagues used a mathematical model to conclude that radiation from mammograms themselves may raise breast cancer risk when these women start getting them before age 34, and may overshadow the benefits of early cancer detection.
Women with such mutations typically have not been exposed previously to high doses of radiation, unlike childhood cancer survivors, meaning that the radiation in mammograms starting at a young age may be more problematic, Oeffinger said.
Editing by Maggie Fox and Bill Trott