NEW YORK (Reuters Health) - As a treatment for breast cancer, radiation, even modern regimens, appears to increase the risk of cardiovascular disease, according to a report in the Journal of the National Cancer Institute for March 7.

Earlier reports have indicated that radiotherapy regimens used in the 1970s elevate heart disease risk, but it has been less clear if more recent regimens also increase the risk.

Apart from the "clear benefits" of radiotherapy, doctors should still be aware of the potentially increased risk of cardiovascular disease following specific radiotherapy regimens in long-term breast cancer survivors, Dr. Flora E. van Leeuwen, from the Netherlands Cancer Institute in Amsterdam, and colleagues note in the report.

A total of 942 cardiovascular events were logged during a median follow-up period of 18 years.

According to the results, radiation that was limited to the breast did not increase the risk of cardiovascular disease. Inclusion of the surrounding breast tissue, however, did increase the risk.

Radiation to the breast and surrounding tissue performed in the 1970s appeared to increase the risk of heart attack and heart failure by 2.55- and 1.72-fold, respectively, compared with no radiation.

By contrast, radiotherapy in the 1980s did not raise the risk of heart attack, but was associated with 2.66- and 3.17-fold increased risks of heart failure and heart valve dysfunction, respectively.

In the 1980s, adding chemotherapy to radiotherapy increased the risk of congestive heart failure by 1.85-fold. Moreover, a 3-fold increased risk of heart attack was seen in radiotherapy-treated patients who also smoked.

In a related editorial, Dr. Sharon H. Giordano and Dr. Gabriel N. Hortobagyi, from the M.D. Anderson Cancer Center in Houston, comment that the study "provides important new information on the cardiac toxicity of radiation therapy."

They also praise the study's methodology, calling the 18-year follow-up period "impressively long" and citing certain unique features, including evaluation of both morbidity and mortality, and comparison of toxicity by radiation fields.