The results of a study confirm that girls who undergo radiation for cancer in childhood have an increased long-term risk of developing breast cancer, regardless of their age at the time of treatment.
When such treatment included a high dose to the ovaries, however, women seemed to be protected against future breast cancer risk.
Radiation is a common, and highly effective, treatment for cancers such as Hodgkin's lymphoma, and adolescents and adults who receive such treatments are known to be at higher risk of developing breast cancer late in life, Dr. Peter D. Inskip of the National Cancer Institute, Bethesda, Maryland, and colleagues note in their report.
Inskip's team studied 120 women diagnosed with cancer when they were younger than 21 years old, were treated between 1970 and 1986, and survived for at least 5 years.
Those cases were each compared with four women who developed cancer at the same age but did not receive radiation.
Overall, chemotherapy for the initial cancer did not increase the risk of a second cancer. However, the more radiation a woman received as a child, the higher her risk of a later tumor, Inskip and colleagues report in the Journal of Clinical Oncology.
However, according to the researchers, the risk associated with radiation treatment of the breasts was "sharply reduced" in women whose treatment of the initial cancer included a high dose of radiation to the ovaries.
Because the women in the study were relatively young, there may still be effects later in life that were not yet seen, the authors point out.