Even low doses of chest radiation in childhood boosts breast cancer risk via City of Hope

Radiation therapy can help cure many children facing Hodgkin lymphoma and other cancers. When the radiation is delivered to a girl’s chest, however, it can lead to a marked increase in breast cancer risk later in life.

Smita Bhatia, M.D.
In a new study, Smita Bhatia, M.D., found that women who received even low doses of radiation therapy to their chests as children have an increased breast cancer risk later in life.
A recent multi-institutional study that included City of Hope’s Smita Bhatia, M.D., the Ruth Ziegler Chair in Population Sciences, examined the long-term effects of chest radiation on female survivors of childhood cancers, primarily Hodgkin lymphoma. The researchers wanted to determine whether more current therapies using less radiation could reduce the breast cancer risk, and if the amount of area exposed was a factor.

Past research has shown that standard doses of radiation therapy to the chest increase breast cancer risk, with incidence rates among these women ranging from 5 percent to 14 percent by age 40.

For the current chest radiation study, lead author Chaya Moskowitz, Ph.D., of Memorial Sloan Kettering Cancer Center in New York, and the research team looked at more than 1,200 women who received various amounts of radiation in treatment of childhood cancers. They found that even women who received lower amounts of radiation as children still were much more likely to develop breast cancer than the average woman, with as many as 30 percent developing breast cancer by age 50.
The scientists also examined whether the amount of tissue exposed to those lower levels of radiation made a difference. While less exposure meant less risk, the risk was still higher than the average woman’s. The researchers found a significant rise in breast cancer risk for women as the amount of tissue exposure increased.

Further, the study compared — possibly for the first time — these women’s risk of breast cancer with that of women with mutations in their BRCA1 genes. That’s the mutation that prompted Angelina Jolie to undergo surgery to remove her breasts to prevent breast cancer, known as a prophylactic surgery. The scientists found that the survivor’s risk by age 50 was nearly the same as if they had BRCA1 mutations.

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