Researchers report in a new study that breast cancer radiation therapy does increase a woman’s risk of suffering a heart attack or other heart problems. However, the increase is small enough that it does not appear to outweigh the benefits of the treatment.
The study was published in the New England Journal of Medicine on March 13, looking at concerns over the fact that radiotherapy for breast cancer results in incidental exposure of the heart to ionizing radiation.
Researchers found that those who received the treatments do experience a small increase in ischemic heart disease risk.
The population-based, case-control study of major heart problems involved 2,168 women who received radiation treatment for breast cancer. The study included 963 women who had major coronary events and 1,205 controls in Sweden and Denmark between 1958 and 2001.
The average dose of radiation to the heart of women who underwent radiotherapy for breast cancer was 4.9 Gray, with a range between 0.03 to 27.72. Women with breast cancer in the left breast received an average of 6.6 gray, while women with tumors in the right breast received an average of 2.9 gray.
According to the findings, the rate of major coronary events increase linearly by 7.4% for every Gray of radiation the heart received.
A Gray is a unit of measurement used to determine how much ionizing radiation an object has absorbed. One gray equals the absorption of one joule of energy per kilogram of matter.
The increase in the risk of actual heart problems, like heart attacks, appears to begin about five years after exposure, and continues for at least 20 ears. The researchers found that women with preexisting cardiac risk factors have a greater absolute increase in risk from radiotherapy than other women with breast cancer.