Women who had radiation to the chest as children to treat a cancer other than breast cancer, such as Hodgkin lymphoma (cancer of the immune system) or non-Hodgkin lymphoma, have a higher risk of breast cancer.
A new study suggests this elevated risk is about 20 times higher than average -- even higher than doctors thought.
The research was published online on April 21, 2014 by the Journal of Clinical Oncology. Read the abstract of “Breast Cancer After Chest Radiation Therapy for Childhood Cancer.”
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 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 records of 1,230 women who survived childhood cancer. All the women had radiation therapy to the chest area to treat the childhood cancer. The women have been followed for between 20 and 46 years.
Overall, 203 of the women developed breast cancer. For women at average risk, doctors would expect to see 9.3 breast cancer cases in this many women.
About half the women developed breast cancer up to 23 years after they were diagnosed with childhood cancer and the other half developed breast cancer 24 or more years after being diagnosed with childhood cancer. About 30% of the women had developed breast cancer by the time they were 50 years old.
The increase in risk seemed to be linked to the size of the area that received radiation:
- women who received a lower dose of radiation (2 to 20 Gy) to a large area (the entire lung area) had a risk of breast cancer that was 43.6 times higher than average
- women who received a higher dose of radiation (about 40 Gy) to the lymph nodes in the neck, chest, and armpits (the mantle field) had a risk of breast cancer that was 24 times higher than average
It’s important to know that high-dose mantle radiation is no longer used to treat childhood Hodgkin lymphoma.
The women who received childhood radiation to the chest and then developed breast cancer were more likely to die from breast cancer than average. Of the women in the study who developed breast cancer, almost 20% died of the disease within 10 years of being diagnosed. This is double the number of women with average risk.
The researchers also compared the breast cancer risk of childhood cancer survivors to the breast cancer risk of women who have an abnormal BRCA1 or BRCA2 gene.
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 is also higher than average.
The risk of developing breast cancer by age 50 was:
- 31% for women with an abnormal BRCA1 gene
- 10% for women with an abnormal BRCA2 gene
- 35% for women who had childhood Hodgkin lymphoma
Women who had other childhood cancers had a 15% risk of developing breast cancer by age 45 -- the researchers didn’t have enough information to estimate these women’s risk by age 50.
So women who had childhood Hodgkin lymphoma and women who have an abnormal BRCA1 gene essentially had the same level of elevated risk.
This 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 heart and lung disease as well as 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 most likely 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.