Incidence of heart disease and functional significance of changes in the electrocardiogram 10 years after radiotherapy for breast cancer.

Late cardiac complications after radiotherapy for breast cancer was studied in 197 patients examined before, 6 months after, and 10 years after treatment. The 10-year follow-up was done by survey of the files of patients who had died and re-examination of patients who were alive and free of cancer. Among 95 patients who died, 3 died of cardiopulmonary diseases. Autopsy in 32 patients showed serious cardiac abnormalities in 3. Of 102 patients alive at follow-up, 3 reported heart symptoms. Sixty-nine patients participated in the re-examination. Electrocardiogram (ECG) abnormalities were found in 19% of these patients before treatment; in 45% at 6 months, essentially due to T-wave changes in patients who had received left-sided irradiation; and in 45% at 10 years, with fewer T-wave abnormalities but more ST depression and ectopic beats. Average working capacity was 83 W before, 81 W at 6 months, and 84 W at ten years. Average heart volume was 680 ml before, 689 ml at 6 months, and 718 ml (P less than 0.01) 10 years after treatment. In conclusion, there was a high incidence of ECG T-wave changes, but they were reversible, and the perimyocardial damage indicated was functionally insignificant. The incidence of serious cardiac complications was low.