TUESDAY, July 21 (HealthDay News) -- Female survivors of childhood cancer have an increased risk of breast cancer that has a linear relationship with radiation dose, according to a study published online July 20 in the Journal of Clinical Oncology.
Peter D. Inskip, of the National Cancer Institute in Bethesda, Md., and colleagues conducted a case-control study of five-year cancer survivors treated between 1970 and 1986 that included 120 breast cancer patients who were each matched (by age of diagnosis with childhood cancer and number of years since the childhood cancer) to four selected controls.
The researchers found that compared to survivors who did not receive radiation, those who received local breast doses of 40 Gy were 11 times more likely to develop breast cancer. They also found that the carcinogenic effects of breast irradiation were reduced by irradiation of the ovaries at doses above 5 Gy. Women who received a breast dose of 40 Gy and an ovarian dose greater than 5 Gy were only 3.4 times more likely than nonirradiated women to develop breast cancer.
"These data point to an important role of hormonal stimulation on radiation-related breast cancer," the authors conclude. "The cohort is still relatively young, and the largest part of the radiation-related absolute excess occurrence of breast cancer may yet be seen."
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