Women who overcome breast cancer have every reason to celebrate. But a heart filled with joy may also be a heart damaged by life-saving cancer therapies, a growing body of research shows.
“Most breast cancer therapies today – including new treatments still under development – increase long-term risk of cardiovascular disease,” said Lee W. Jones, Ph.D., an exercise physiologist and assistant professor in the Department of Surgery at Duke University Medical Center, Durham, NC.
“We don’t know exactly how large the added risk is, but we believe it’s substantial. Recent gains in breast-cancer-specific survival could be markedly diminished by an increase in the long-term risk of cardiovascular death.”
In an article published in the October 9, 2007, issue of the Journal of the American College of Cardiology (JACC), Dr. Jones and his colleagues call for taking the long view in breast cancer therapy—focusing not just on the immediate cancer threat but also on long-term cardiovascular health.
“There are millions of American women living with breast cancer,” said Pamela S. Douglas, M.D., chief of cardiology at Duke and a co-author of the JACC paper. “It’s important that they don’t squander their second lease on life.”
Breast cancer is the most common form of cancer among American women, accounting for more than 200,000 new cases each year. Thanks to new and better therapies, death rates from breast cancer are falling dramatically—by nearly 24 percent between 1990 and 2000, for example. That means that more women than ever before will live for years with the cardiovascular effects of cancer therapy.
Many middle-aged and older women who are diagnosed with breast cancer already have age-related risk factors for cardiovascular disease, such as high blood pressure. In addition, physical inactivity and obesity have been linked to both breast cancer and heart disease. This pre-existing risk only heightens the likelihood that breast cancer therapies will harm the cardiovascular system.
Cancer therapies damage the heart and blood vessels in a variety of ways. Conventional chemotherapeutic agents silently injure the heart muscle in as many as half of patients, diminishing the heart’s pumping ability and increasing the risk of heart failure years later. Radiation therapy can cause scarring and tissue damage in the heart and lungs. Herceptin, a monoclonal antibody used in treating women with high-risk genetic profiles, is also associated with cardiac toxicity and heart failure. Experimental therapies that limit the growth of blood vessels in tumors can cause abnormal blood clotting, high blood pressure and reduced cardiac function. Even hormone therapy with aromatase inhibitors raises concern, given the long-term reduction in estrogen levels. Equally important, many women become physically inactive during cancer therapy, resulting in significant weight gain.
Keeping heart health in mind during breast cancer therapy can be as simple as performing a baseline evaluation of standard cardiovascular risk factors including age, blood pressure, cholesterol levels, smoking history and body weight. Depending on the results, the patient may need a prescription or a referral to a cardiologist.
Exercise is an important component of any treatment program. Even during cancer therapy, exercise will likely help a woman to feel better. In addition, Dr. Jones is doing research to determine whether exercise improves blood flow to the tumor, thereby enhancing delivery of cancer drugs to their intended target.
He is also studying whether exercise can protect the heart against the harmful effects of chemotherapy, for example, by improving blood pressure, reducing body weight and strengthening the heart’s pumping ability. “If exercise can improve tumor outcomes while protecting the cardiovascular system, that would be a very important finding,” he said.
Dr. Jones believes that if oncologists emphasize the importance of exercise, patients will listen. “Women with breast cancer are very motivated, well-informed and proactive,” Dr. Jones said. “They’re very interested in knowing how to live healthy lives.”