What is the effect of ionizing radiation on a women's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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The knowledge that ionizing radiation to the chest in cumulative moderate-to-high doses (eg, 1-3 Gy) at young ages substantially increases breast cancer risk comes from several lines of evidence, including atomic bomb survivor studies, studies of diagnostic-therapeutic uses of radiation, and occupational studies. Among survivors of the atomic bombing of Hiroshima and Nagasaki, breast cancer risk was strongly associated with estimated breast tissue dose of radiation. [21] Further, the excess risk of breast cancer associated with each radiation dose depended heavily upon the age at the time of the bombing, being highest for women exposed before age ten years. For women exposed after age 40 years, there was no significant elevation in subsequent breast cancer risk.

Studies of diagnostic radiation have revealed a similar pattern of excess risk of breast cancer associated both with higher doses and with younger ages at exposure. Studies of therapeutic radiation for nonmalignant and malignant disease have revealed the same pattern. In a study of women exposed to radiation therapy to the chest as treatment for Hodgkin disease, the excess risk of breast cancer was dependent on dose and age at irradiation. [82]

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