The radiation therapy regimens used to treat breast cancer in the 1970s and early 1980s increase the risk of death from heart disease and lung cancer, according to a study published in Lancet Oncology. Breast cancer patients who received radiation therapy during that time may wish to speak with their physician regarding screening for heart or lung disease.

Radiation therapy to the breast for early-stage breast cancer is a common treatment modality. Unfortunately, radiation therapy to the breast cancer may also expose the heart and lungs to radiation. When the heart and lungs are exposed, the amount of radiation they receive varies with the side of the body that is treated. Radiation therapy to the left breast results in more radiation exposure to the heart than radiation therapy to the right breast. In the lungs, radiation exposure is the greatest for the lung on the side of the body that is irradiated.

To assess the effect of radiation therapy for breast cancer on subsequent heart disease and lung cancer risk, the researchers evaluated 308,861 women with early breast cancer diagnosed between 1973 and 2001. These women were identified from the U.S. Surveillance Epidemiology and End Results (SEER) cancer registries. The researchers evaluated whether women who received radiation for a left-sided breast cancer were more likely to die of heart disease, and whether lung cancer occurred more commonly on the side of the body that had been irradiated. Women with cancer in both breasts were excluded.

Among women diagnosed with breast cancer between 1973 and 1982, those who received radiation to the left breast were more likely to die of heart disease than women who received radiation to the right breast. After 10 to 14 years of follow-up, women who received radiation to the left breast were 42 percent more likely to die of heart disease than women who received radiation to the right breast; after 15 years of follow-up, they were 58 percent more likely to die of heart disease. There was no evidence of an association between the side of the breast cancer (left or right) and heart disease mortality among women who received radiation during later years (1983-2001), but there is less follow-up available for these women.

Radiation therapy for breast cancer between 1973 and 1982 also appeared to increase the risk of dying from lung cancer. Among women who received radiation and also developed lung cancer, the lung cancer most often developed on the side of the body that had been irradiated. This effect was especially apparent after 15 years of follow-up. There was no evidence of an association between lung cancer and radiation among women diagnosed with breast cancer between 1983 and 2001.

The researchers conclude that the radiation therapy regimens used for breast cancer in the 1970s and early 1980s increase a woman’s long-term risk of death from heart disease and lung cancer. Women who received radiation therapy for breast cancer during these years may wish to talk with their doctor about their heart and lung health. More recent radiation therapy regimens for breast cancer are likely to have much less of an effect on the heart and lungs.

Reference: Darby SC, McGale P, Taylor CW et al. Long-term mortality from heart disease and lung cancer after radiotherapy for early breast cancer: prospective cohort study of about 300,000 women in US SEER cancer registries. Lancet Oncology. 2005;6:557-65.

Additional Information:Radiation Therapy for Breast Cancer

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