Women who have survived breast cancer may have to fight another killer down the road -- heart failure, researchers report.
They found a much higher rate of heart failure among breast cancer survivors than has previously been reported, and said their findings likely reflect the real-world risks that women have. The 12,000 women studied for the report had a 20 percent risk of developing heart failure over just five years if they got a common chemotherapy regimen, compared to just 3.5 percent of breast cancer patients who did not get chemo.
"I think these drugs are critical to improving breast cancer survival," said Erin Aiello Bowles of the Seattle-based Group Health Research Institute, who led the study published in the Journal of the National Cancer Institute. "But these drugs are toxic. They are meant to target disease but they can often damage other parts of the body."
Clinical trials of breast cancer patients -- designed to discover whether drugs fight disease and to show how safe they are -- have shown that the drugs can damage the heart and cause higher rates of heart failure. They generally demonstrate about a 4 percent increase in heart failure over three to five years for women getting chemo. But clinical trials usually involve a select group of patients who are healthy in other ways.
Bowles said her team set out to look at real-world patients of all ages and with a range of health conditions on top of their breast cancer. They went through the medical records of women at eight health systems who were treated between 1999 and 2007 with two very common cancer drugs: a group of drugs called anthracyclines, such as adriamycin, and a targeted antibody drug called Herceptin or trastuzumab.
Each drug raised the risk on its own, but the combination greatly raised heart failure rates.
"It is important to note that these rates do vary by age," Bowles said in a telephone interview. "They are much lower in the younger women." More than 40 percent of the women over the age of 75 who got a combination of an anthracycline and Herceptin also developed heart failure within five years. Just 13.7 percent of the breast cancer patients that age who did not get chemo developed heart failure.
The study highlights a growing problem. The American Cancer Society estimates there are 12 million cancer survivors alive in the United States now. As many cancer patients survive their disease and lead ever-longer lives, they find they must fight second battles against the long-term effects of the treatments that saved their lives. Even so-called targeted therapies, which were designed to better target tumor cells while leaving healthy tissue alone, have been shown to cause long-lasting damage.
And as they leave the care of a specialized oncologist and return to day-to-day care, they may not know they’re at special risk of other conditions – and their primary care doctors may not be aware, either. The American Society of Clinical Oncology has been warning about the problem for years, and released research at its annual meeting last June showing that 94 percent of primary care doctors didn't know about the potential long-term effects of drugs commonly used to treat breast and prostate cancer.
Breast cancer is the leading cancer killer of U.S. women, after lung cancer. It is diagnosed in more than 220,000 women a year, according to the American Cancer Society, and will kill nearly 40,000 this year. About 20 percent of cases are a kind called HER-2 positive, and Herceptin was formulated to especially target this kind. It’s very effective and has saved thousands of lives, but it was known to also damage the heart, although doctors don’t understand just how.
Heart failure is also very common. The National Heart, Lung and Blood Institute estimates 4.8 million Americans have congestive heart failure, which is a chronic condition in which the heart doesn’t pump blood effectively. Half of patients with heart failure die within five years, and 400,000 people get newly diagnosed every year.
So what can women do if they’ve had chemo for breast cancer and want to watch their hearts?
Cardiologist Dr. Larry Allen of the University of Colorado in Denver, who also worked on the study, said they first of all need to be educated about what drugs they have taken and what the side-effects are.
“Second, patients should ask about what heart tests may be indicated before, during, and after treatment,” Allen said in a statement. These may include tests of how well the heart is pumping blood – tests that most women won’t get during a routine physical or well-woman visit.
“Third, in addition to allowing doctors to monitor for heart problems, patients can monitor themselves for worsening heart function by understanding how heart problems may present -- including shortness of breath especially when lying flat, leg swelling, palpitations/heart fluttering, and exercise intolerance (these symptoms can represent non-heart disease too, but generally warrant additional evaluation),” Allen added.
“Unfortunately, it is unknown if medications that are typically used to treat heart failure (such as beta-blockers and ACE inhibitors) might protect against heart damage from certain chemotherapy.”