Radiation treatments -- especially those received more than five years ago -- and the drug Herceptin have been linked to heart problems in women with breast cancer.

Both radiation and the drug Herceptin have been implicated in two separate studies. However, doctors note that the associated heart problems are often preventable or treatable, and they have characterized the elevated risk level as "acceptable." They stress that women who have breast cancer should not be afraid to get the treatment they need.

In the study involving radiation, scientists at the University of Pennsylvania followed 961 women who were treated for early stage breast cancer between 1977 and 1994. Radiation to the left breast was associated with greater risk of heart disease than radiation on the right. Heart attacks were more common among the patients who had radiation on the left than those who received it on the right, as well. However, there was no apparent change in death rates from heart disease due to the treatments.

Presumably, the increased risk was due to the effect of the radiation on parts of the heart and on coronary arteries. However, the problems did not emerge until 10 years or more following the treatment.

"Women receiving radiation to the left side of their chest need to be aware of this risk," said lead author Eleanor Harris, MD, who is now Associate Professor and Clinical Director of Radiation Oncology at the H. Lee Moffitt Cancer Center & Research Institute in Tampa, Florida. She urged them to "take the appropriate steps to monitor their cardiovascular health."

A history of heart disease, high blood pressure or elevated cholesterol levels prior to the cancer treatment were found to further increase the risk.

Today's new treatment methodologies do not carry a similar risk for women today, since the heart is rarely exposed. The study results have greater implications for women who received radiation five or more years ago. Those patients should be especially vigilant about monitoring their blood pressure and cholesterol levels, say the researchers.

In the other study, investigators at the MD Anderson Cancer Center followed 173 patients who were treated with Herceptin for breast cancer that had spread.

Of those who used the drug for at least a year, 28 percent subsequently experienced a decline in their heart's ability to pump. Most responded well to medication, and the problem was reversed.

One woman in that study group died from heart failure.

Francisco Esteva, MD, Associate Professor of Medicine at M.D. Anderson and the study's senior author, pointed out that some patients will experience cardiac toxicity even though long term use of Herceptin appears to be safe. "The good news is that this toxicity appears to be reversible with medical treatment such as beta-blockers and ACE inhibitors," he commented.