Chest Radiation as a Child Ups Risk for Breast Cancer Later in Life

Women treated with chest radiation as children have a significantly increased risk for developing breast cancer later in life, according to the results of a recent study.

In fact, researchers, led by Chaya S. Moskowitz, PhD, of the department of epidemiology and biostatistics at Memorial Sloan Kettering Cancer Center, estimated that these women have a risk for breast cancer similar to that of BRCA gene mutation carrier.

“Women who have been treated with high doses of chest radiation for Hodgkin lymphoma have previously been shown to have a high risk of breast cancer, but how this risk compares to the risk of breast cancer in another population thought to have one of the highest risks of breast cancer, women with BRCA mutations, is unknown,” Moskowitz told Diagnostic Imaging. “Further, the risk of breast cancer in women treated with lower doses of radiation has not previously been well-characterized.”

Moskowitz and colleagues evaluated 1,230 female childhood cancer survivors treated with chest irradiation for their cumulative breast cancer risk. Data on the cancer diagnosis and radiation exposure, including radiation field and dose, were extracted from medical records. The results of the study were published in The Journal of Clinical Oncology.

“The Children’s Oncology Group recommends annual breast cancer screening with mammography and breast MRI for women who were treated with at least 20 Gy of chest radiation,” Moskowitz said. “We found that women treated with lower doses of radiation to a large area of their chest who are not covered by the Children’s Oncology Group guidelines also have a very high risk of breast cancer and may derive benefit from a similar breast cancer screening schedule.”

Data revealed that women treated even with doses of radiation from 10 Gy to 19 Gy had an increased risk for breast cancer (standardized incidence ratio=30.6; 95 percent CI, 18.4-50.9). Overall, survivors treated with a median dose of 14 Gy (range from 2 Gy to 20 Gy) to a large volume, such as the whole lung field, had a high risk of breast cancer (SIR=43.6; 95 percent CI, 27.2-70.3). Survivors treated with a high dose of radiation to the mantle field also had an increased risk for breast cancer (SIR=24.2; 95 percent CI, 20.7-28.3).

“We found that survivors of Hodgkin lymphoma treated with chest radiation have a risk of breast cancer that is comparable to the risk of breast cancer in women with BRCA1 mutations,” Moskowitz said. “Further, we found that survivors of other childhood cancers who were treated with chest radiation also have a high risk of breast cancer, similar to the risk of breast cancer seen in carriers of BRCA2 mutations.”

By age 50, survivors had a cumulative incidence for breast cancer of 30 percent; survivors of Hodgkin’s lymphoma had a cumulative incidence of 35 percent. Results indicated that the breast cancer-specific mortality at five years and 10 years was 12 percent and 19 percent, respectively.