Risks not higher for early-stage breast cancer treated with external beam radiotherapy
Patients with early-stage breast cancer who receive external beam therapy are not at higher risk for serious long-term side effects in the chest area, including increases in deaths from cardiac disease and secondary malignancies. These research results were presented at the American Society for Radiation Oncology's 55th Annual Meeting in Atlanta, Georgia.
The study utilized patient information from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database. It evaluated women identified as having primary Stage T1aN0 breast cancer (tumor of 5mm or less that has not spread to the lymph nodes), who received surgery, with or without postoperative radiation therapy, between 1990 and 1997. The analysis was done to determine if external beam radiotherapy was associated with increased mortality due to breast cancer, secondary cancer in the chest area, or cardiac conditions for these patients; only patients with breast cancer identified as the first malignancy were included. The women had a median age of 55 to 59 years and were divided into two groups: 2,397 who received external beam radiotherapy after surgery, and 2,988 who did not receive it after surgery.
Cause-of-death codes were used to identify cardiac mortality, breast cancer mortality, and deaths from secondary chest cancers in order to assess overall survival, breast cancer survival, second-tumor specific survival and cardiac-cause specific survival, and then compared between those who did or did not receive external beam radiotherapy.
At 10 years post-treatment, overall survival rates were 91.6% for the patients who received external beam radiotherapy and 87% for those who did not receive external beam radiotherapy; breast cancer survival rates were 97% with and 95.7% without external beam radiotherapy; cardiac-cause specific survival was 96.7% with and 92.7% without external beam radiotherapy.
After a median follow-up of 14 years, no statistically significant difference occurred in deaths from subsequent nonbreast cancers in the chest area, the majority of which were lung cancers. The number of deaths from cardiac causes was not significantly higher for those patients treated with external beam radiotherapy for left-sided breast cancer, compared with those with right-sided breast cancer among the patient sample and time period reviewed. More women who did not receive external beam radiotherapy died from all causes, including cardiac causes, suggesting that those patients had worse general health conditions than the women who received radiation therapy.