Radiotherapy for breast cancer linked with increased CV mortality risk

Bouillon K. J Am Coll Cardiol. 2011;57:445-452.

Issue: March 2011

Women with breast cancer who underwent radiotherapy up until the mid-1980s were more likely to die of a cardiovascular disease, according to results from a long-term study.

Researchers in France and Sweden tracked mortality in 4,456 women who survived at least 5 years of breast cancer radiotherapy at a single center. The women received the therapy between 1954 and 1984, and were followed until the end of 2003, for an average of 28 years.

“During the second part of the 20th century, the radiation doses delivered to these structures were high. … Although radiation therapy for breast cancer has long been known to induce damage in the heart, it is still important to investigate the magnitude of the risk of cardiovascular disease following radiotherapy for breast cancer,” the researchers wrote. They added that only a small number of studies have conducted the long-term follow-up necessary to assess the true risk of CV mortality.

From 1954 to 1957, women received radiotherapy from a 200-kV X-ray machine. From the late 1950s onward, cobalt-60 units were gradually introduced, the researchers wrote. They observed 421 total deaths due to CVD. Of these, 236 were due to cardiac diseases, conferring a 1.76-fold (95% CI, 1.34-2.31) higher risk of cardiac mortality for women who underwent radiotherapy. For vascular diseases, the women had a 1.33-fold (95% CI, 0.99-1.80) higher risk of dying.

In total, the excess risk of death due to radiotherapy was 56% for CVD and 76% for cardiac diseases, the researchers wrote. “In our cohort, among the cardiac diseases, the highest risk associated with radiotherapy was observed for death from valvular heart disease (RR=9.01; 95% CI, 1.16-70),” they wrote.

Women who were treated for left-sided breast cancer had a 1.56-fold (95% CI, 1.27-1.90) higher risk of dying from cardiac disease than women treated for right-sided breast cancer, a risk that was positively correlated with time since diagnosis (P=.05).

“Very few women received chemotherapy in this cohort. Therefore, we were not able to investigate in detail the impact of this treatment on cardiovascular mortality. Similarly, we were not able to investigate the role of hormonal suppression because all women who had received hormonal therapy had also received radiotherapy,” the researchers wrote.

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