ATLANTA – A decade after treatment for early-stage breast cancer, women who underwent surgery and radiation had higher survival rates than women who had surgery alone, with no increase in radiation-related cardiac or secondary cancer deaths, investigators reported at the annual meeting of the American Society for Radiation Oncology.
An analysis of Surveillance, Epidemiology and End Results (SEER) data on women treated for stage TIA N0 breast cancer in their mid to late 50s showed that after a median follow-up of 14 years, 10-year overall survival among the 2,397 women who received lumpectomy or mastectomy and radiation was 91.6%, compared with 87% for 2,988 women who had lumpectomy or mastectomy only (P less than .001).
Ten-year cardiac cause–specific survival was 96.7% vs. 92.7% (P less than .001), respectively. Breast cancer–specific survival was also higher among women who had undergone radiation, at 97% vs. 95.7% (P = .01), reported Dr. Jason C. Ye, a resident in radiation oncology at Weill Cornell Medical College, New York.
Dr. Jason Ye
The data also suggest that breast irradiation does not increase the risk of lung cancer death, which occurred in 6 patients (1.9%) who underwent lumpectomy and radiation, and in 48 (1.6%) of those who had lumpectomies only, a difference that was not significant.
Dr. Ye noted, however, that between-group differences may begin to show up with longer follow-up.
"Although 14 years is a long time, studies have found increases in cardiac mortality and secondary cancers at 20 and 30 years after radiation. Also, there might have been a selection bias by physicians treating at the time, based on patients’ comorbidities and the patient’s health status. This might explain why the overall survival and the cardiac cause–specific survival were different between the two groups, with the no-radiation arm doing worse," he said at a media briefing.
In addition, changes in techniques introduced since the 1990s, such as three-dimensional conformal radiation, prone irradiation, hypofractionation, and intensity-modulated radiation therapy, may have effects on cardiac-specific and overall survival rates in the future, Dr. Ye said.
Dr. Ye and his colleagues reviewed SEER records on 5,385 women treated for early breast cancer during 1990-1997, and stratified them according to treatment with external-beam radiation or no radiation.
They included only patients with stage TIA N0 breast cancer identified as their first malignancy.
The authors used cause-of-death codes to identify cardiac deaths (either from cardiac disease or from atherosclerosis, breast cancer mortality, and deaths from second cancers in the chest area).
Radiation was associated with significantly lower overall mortality (relative risk, 0.69; P less than .001), breast cancer mortality (RR, 0.75; P = .02), and cardiac mortality (RR, 0.53; P less than .001).
Women with tumors in the left breast, whose hearts would presumably receive a larger dose of radiation than women with right breast tumors, were not at increased risk for cardiac-specific death. Deaths from second cancers included lung cancer in 2%; lymphomas and leukemias, each in 0.4%; soft-tissue malignancies (including the heart) in 0.06%; and cancer of the esophagus in 0.04%.
There were no significant differences between the radiation and no-radiation groups in incidence of death from second cancers.
The study was supported by the National Cancer Institute. Dr. Ye reported having no relevant disclosures.