Last week brought good news about cancer. Deaths from most forms of the disease have been falling in the United States since 1993; between 2002 and 2004, the rate of decline among men and women doubled. Breast cancer figures prominently here: More than 240,000 women are affected yearly, and the ranks of survivors have swelled beyond 2.4 million. The success is a tribute to two decades of early-detection campaigns, including mammograms, and the many recent strides in breast cancer therapy.
But success brings its own challenges, and this happy news for women comes with the sobering reality that the heart pays a price for ridding the body of breast cancer. That is, as breast cancer deaths move down, heart attacks and heart failure risk related to the curative treatments inch up. In fact, for many survivors of breast cancer today, pleased to be around to see those few gray hairs set in, the risk of heart disease is greater than the chance of having recurrent cancer. Living for the long haul calls on survivors to pay added attention to these added risks—and manage them.
Chemotherapy and radiation treatments are now standard fare in breast cancer therapy and are well known to bring on collateral damage to hair follicles and bone marrow as the price of admission to the club of cancer survivors. Less recognized are the cardiac side effects that occur in as many as 20 percent of patients. Often not evident to them, the effects include transient bouts of hypertension, abnormal heartbeats, heart inflammation, and weakening heart muscle and occur more commonly in older women. Some drugs pose greater risks to the heart than others. Tamoxifen, for example, has no adverse cardiac effects, whereas a class of drugs called the anthracyclines, highly effective in combating breast cancer, are particularly toxic to heart muscle in a cumulative and lasting way. Even when oncologists strictly limit the net dose that's administered to any one patient, some still develop a low level of heart muscle injury that confers vulnerability to heart failure later in life.
Radiation therapy for breast cancer has its way with the heart as well, and here it's a matter of geography. The heart lies behind the left breast and cannot entirely escape the anticancer rays. (Not surprisingly, treatment poses a greater danger when it's administered to the left as opposed to the right breast.) Radiation can damage the lining of the coronary arteries and some heart cells, leaving scars behind; typically, the consequences don't show up for 20 or so years, with a small but significant increase in heart failure and heart attacks. The left anterior descending coronary artery, the principal artery that feeds the left ventricle, is especially vulnerable, as it lies on the surface of the heart close to the chest wall. And any cardiac surgeon will tell you that the mammary arteries favored for coronary bypass operations can be damaged as well. Newer technology decreases the radiation exposure outside the target area and seems to lessen these effects, but the heart cannot be entirely spared.
Fixable factors. The cardiac effects of individual drugs or radiation pile on when given in combination, as they typically are, creating a risk of heart disease that is more than additive. But even if these unique risks from cancer treatment linger, the well-known threats of smoking, high blood pressure, elevated cholesterol, obesity, and inactivity are all fixable. Those who have so courageously taken on breast cancer surely have the strength and motivation to attack them to ensure that their hard-won cancer battle is not in vain.
First, a breast cancer survivor needs to know her individual heart risks, including specific information about her drugs and radiation treatments. These exposures should be discussed with her primary care doctor, and a baseline evaluation of heart function after therapy makes sense as well. Then, she can begin to control the controllable risk factors that will aggravate any pre-existing cardiac vulnerability. One good place to start is regular exercise, which may also protect against breast cancer recurrence.