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Radiation Therapy to Chest as Child Increases Breast Cancer Risk in Adulthood

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A study found that women treated for childhood cancer with radiation therapy to the chest area have a much higher-than-average risk of breast cancer later in life. This risk is about the same as it is for women who have an abnormal breast cancer gene.

The study was presented at the 2012 American Society of Clinical Oncology Annual Meeting. Read the abstract of Risk of breast cancer in childhood cancer survivors treated with chest radiation.

In recent decades, some of the most important medical discoveries have been in treating childhood cancer. Still, some childhood cancer patients develop a second cancer or another serious medical condition later in life that's believed to be related to treatment for childhood cancer. Doctors don’t completely understand why childhood cancer survivors are more likely to be diagnosed with a different cancer later in life. For some, it could be that genetics that make them more likely to develop cancer. For others, the higher cancer risk is probably related to the childhood cancer treatment. For example, radiation used to treat childhood cancer also can affect normal cells that are exposed to the radiation, causing a new, different cancer -- like breast cancer -- to develop decades later.

As part of the Childhood Cancer Survivor Study, researchers reviewed the health histories of 1,268 women who survived childhood cancer. All the women had radiation therapy to the chest area to treat the childhood cancer. Half the women had been followed for more than 26 years since childhood cancer diagnosis; the other women were followed for shorter times.

The researchers found that 175 of the women were diagnosed with breast cancer from 7 to 38 years after childhood cancer treatment. The women’s ages ranged from 24 to 53 when they were diagnosed with breast cancer.

The researchers projected the overall risk of the women being diagnosed with breast cancer by age 50 and compared it to the breast cancer risk by age 50 of two other groups of women:

  • women with an average breast cancer risk
  • women with either of the two abnormal breast cancer genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two)

Women with an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Their risk of ovarian cancer also is higher than average.

The projected breast cancer risk by age 50 was 24% for women who had been treated with radiation therapy to the chest for childhood cancer. The average breast cancer risk for women by age 50 is 4%.

Breast cancer risk was highest in the women who received higher doses of radiation to the chest area and was similar to the risk of women with an abnormal breast cancer gene:

  • Breast cancer risk by age 50 was projected to be 31% for women who received high-dose radiation therapy (called mantle radiation) to the chest area to treat childhood Hodgkin lymphoma (cancer of the immune system). Breast cancer risk by age 50 also is projected to be 31% for first degree female relatives of someone with an abnormal BRCA1 gene. It’s important to know that high-dose mantle radiation is no longer used to treat childhood Hodgkin lymphoma.
  • Breast cancer risk by age 50 was projected to be 10% for women who received lower-dose radiation therapy to the chest area to treat other childhood cancers. While lower than the risk faced by women who received high-dose childhood radiation, this 10% risk is still higher than the average of 4% and identical to the projected risk by age 50 for first degree female relatives of someone with an abnormal BRCA2 gene.

The study strongly suggests that even when relatively low-dose radiation therapy to the chest area is used to treat childhood cancer, breast cancer risk goes up.

Other research has shown that childhood cancer survivors are at much higher risk for a number of health problems in adulthood, including cancer. Because of these risks, people who have been treated for childhood cancer should take aggressive steps to minimize their risk of another cancer. These people also should have regular screenings for any complications of earlier treatment, including cancer.

If you've been treated in the past for cancer, it's important to regularly see a doctor who:

  • is familiar with your past medical history
  • understands your special risks
  • can give you the necessary counseling, monitoring, and screening for possible complications of your earlier treatment

If your childhood cancer treatment included radiation therapy to the chest area, your risk of breast cancer is probably higher than average. You and your doctor should consider a more aggressive breast cancer screening plan. This plan might include more frequent mammograms starting at an earlier age and possibly using different screening techniques, such as breast MRI.

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