Patt DA et al. (2005) Cardiac morbidity of adjuvant radiotherapy for breast cancer. J Clin Oncol 23: 7475–7482

Radiotherapy following breast-conserving surgery improves overall outcomes and decreases the risk of local recurrence; however, left-sided breast irradiation can cause cardiac damage and might be associated with increased risk of cardiac morbidity. The long-term effects of adjuvant breast irradiation are not well defined, and risk assessment based on early studies might not be valid because modern techniques have reduced the radiation dose and the volume of heart tissue exposed to radiation.

Patt et al. followed women with nonmetastatic breast cancer (8,363 left-sided and 7,907 right-sided) who had received adjuvant radiotherapy between 1986 and 1993. Cox's proportional hazards model was used to compare the incidence of hospitalization caused by ischemic heart disease, valvular heart disease, conduction abnormalities, or cardiomyopathy or heart failure in women with left-sided versus those with right-sided cancer. After a mean follow-up of 9.5 years, there was no significant difference in the rates of hospitalization for cardiac events between women treated with radiotherapy for left-sided and those treated for right-sided breast cancer. The risk of ischemic heart disease increases with time; however, in an additional analysis with 10–15 years of follow-up, there was no difference in left-sided versus right-sided breast cancer.

In summary, the data suggest that modern adjuvant radiotherapy does not cause significant cardiovascular disease. Nevertheless, there is a strong correlation between doses of radiation to the myocardium and risk of death from cardiac events; therefore, additional reductions in myocardial radiation are likely to be beneficial.