According to the findings of new research, women who underwent childhood cancer treatments involving both chemotherapy and radiation may be more likely to develop breast cancer later in life, which may influence guidelines for future surveillance of cancer survivors.
In a study published last week in the medical journal JAMA Pediatrics, researchers with the National Cancer Institute indicate receiving both radiation treatment and chemotherapy during childhood appears to have a significant impact on the breast cancer risk.
Researchers used data from the North America Childhood Cancer Survivor Study to conduct a hospital-based case control study of more than 14,000 childhood cancer survivors who were diagnosed from 1970 to 1986 and had survived more than five years. Of those patients, 271 were women who developed breast cancer later in life at the average age of 39. They were matched with 1,044 control cases by age.
According to the findings, the risk of breast cancer for women was 10 times higher if they received increasing radiation doses to the breast of 10 Gy per dose. Women also faced nearly double the risk of breast cancer with cumulative doses of 100 mg/m2 of chemotherapy. However, the risk was even higher when radiation and chemotherapy treatment were combined. The risk was nearly 20 times higher for a combined dose of 10 Gy or more with chemotherapy doses of 100 mg/m2.
Patients who received higher doses of radiation for ovarian cancers in childhood also faced a risk, but it was much lower. However, most patients who received 15 Gy or more to the ovaries reported never menstruating, or went into menopause within five years of their first cancer diagnosis.
Study authors indicate the doses of radiation used to treat many childhood cancers has been dropping in the last 20 years and the amount of tissue being irradiated has also decreased. However, a similar correlation has not been seen resulting in a lower breast cancer risk later in life.
Researchers speculate this may indicate it has less to do with the dose or amount of radiation, but more to do with the combination of the two types of therapy together.
The findings of the new study can help inform future surveillance guidelines for childhood cancer survivors, the researchers said. Additionally, they indicated it may help focus treatment guidelines so that the best chance of remission can be offered with the lowest future risk of cancer later in life.