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Radiation to Chest for Childhood Cancer Increases Breast Cancer Risk

Radiation therapy to the chest for the treatment of childhood cancer increases a girl’s risk of developing breast cancer at a young age, even if fairly low doses of radiation are given. These results were presented at the 2012 Annual Meeting of the American Society of Clinical Oncology. 

Radiation therapy is an important component of the treatment of several types of childhood cancer. Radiation to the chest, however, can increase the risk of breast cancer. For girls who receive moderate or high levels of radiation (20 Gy or more) to the chest, the Children’s Oncology Group recommends breast cancer screening with annual mammography and breast magnetic resonance imaging (MRI) starting at age 25 or eight years after the radiation (whichever is later).  

To further explore the effects of radiation therapy to the chest (including the effects of lower doses of radiation), researchers conducted a study among more than 1,200 female survivors of childhood cancer; all had received radiation to the chest. Breast cancer risk in these women was compared with the breast cancer risk among women with a BRCA1 or BRCA2 gene mutation. These inherited gene mutations are known to greatly increase a woman’s risk of breast cancer.    

  • Overall, the risk of breast cancer by the age of 50 was 24% among the childhood cancer survivors. In the subset of survivors who had been treated for Hodgkin’s lymphoma, the risk of breast cancer by the age of 50 was 30%. 
  • By comparison, the risk of breast cancer by the age of 50 was 31% among women with a BRCA1 mutation and 10% among women with a BRCA2 mutation. In the general population, the risk of breast cancer by the age of 50 is 4%. 
  • When looking at dose of radiation, the risk of breast cancer by the age of 40 was 7% among girls who had received 10-19 Gy of radiation and 12% among girls who had received 20 Gy or more. Both of these results are much higher than what is observed in the general population. 

This study suggests that for girls who received radiation to the chest for the treatment of childhood cancer, the likelihood of developing breast cancer at a young age is much higher than that of the general population, and similar to what is seen among women with a BRCA mutation. Breast cancer risk is increased even for girls who received lower doses of radiation to the chest, and these girls may benefit from the same breast cancer screening strategy that is recommended for girls who received higher doses of radiation. 

Reference: Moskowitz CS, Chou JF, Wolden SL et al. New insights into the risk of breast cancer in childhood cancer survivors treated with chest radiation: a report from the Childhood Cancer Survivor Study (CCSS) and the Women’s Environmental Cancer and Radiation Epidemiology (WECARE) Study. Paper presented at: 2012 Annual Meeting of the American Society of Clinical Oncology; June 1-5, 2012; Chicago, IL. Abstract CRA9513. 

 

Posted June 14, 2012