In 2002, about 42% of women with breast cancer received adjuvant radiation therapy after surgery. Adjuvant radiation therapy decreases a woman's risk of local recurrence of her cancer but can increase her risk of death from ischemic heart disease. Patients with left-sided breast tumors receive a higher radiation dose to the heart than patients with right-sided tumors. However, modifications in radiation techniques over time have been able to reduce the radiation dose to the heart, which may affect the risk of cardiac death.
To determine whether the risk of death from ischemic heart disease resulting from radiation therapy to the breast has decreased over time, Sharon H. Giordano, M.D., M.P.H., of the University of Texas M. D. Anderson Cancer Center in Houston, and colleagues examined data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. They compared ischemic heart disease mortality in women diagnosed with left-sided versus right-sided breast cancer from 1973 to 1979, 1980 to 1984, and 1985 to 1989.
The researchers found that the risk of death from ischemic heart disease among these women declined over time. Among women diagnosed between 1973 and 1979, those with left-sided tumors had a higher rate of 15-year mortality from ischemic heart disease (13.1%) compared with women with right-sided tumors (10.2%), but there was no statistically significant mortality difference among women diagnosed from 1980 to 1984 (9.4% versus 8.7%) or from 1985 to 1989 (5.8% versus 5.2%). The authors note that the increase in the risk of death from ischemic heart disease was not apparent until late in the first decade of follow-up.
"These encouraging data suggest that advances in radiation techniques have been translated into substantial benefits for women with breast cancer. Whether the risk of ischemic heart disease mortality resulting from radiotherapy has been entirely eliminated cannot be determined definitely from this study. Continued follow-up of the women diagnosed and treated in the late 1980s will be necessary to answer this question," the authors write.
In an editorial, Jack Cuzick, Ph.D., of Cancer Research U.K. in London, discusses the use of radiotherapy in the treatment of breast cancer and how this latest research shows that changes in radiation administration have affected mortality. "Radiotherapy is now used for very-good-prognosis invasive tumors and even for in situ breast cancers, for which life expectancy is almost equal to that of the general population and will exceed 20 years in many cases," he writes. "A major advancement in the use of this modality appears to be emerging, but it is still too early to declare an absolute victory. We owe it to women with breast cancer to remain vigilant and continue follow-up of this and related cohorts for at least another decade."
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JNCI Journal of the National Cancer Institute