Breast Cancer Drug May Harm the Heart More Than Thought
It has been known that women treated with anti-cancer drugs known as anthracyclines and Herceptin (trastuzumab) are at higher risk for heart failure and cardiomyopathy, a weakening of the heart muscle.
But, that information on risks has come primarily from clinical trials, which typically exclude women aged 70 and older and those with co-existing chronic diseases, so it doesn't necessarily give a real-world picture, the researchers noted.
"The risk of heart failure associated with these drugs might be higher than what has been shown in clinical trials," explained study author Erin Aiello Bowles, an epidemiologist at Group Health Research Institute, in Seattle. Her report is published online Aug. 30 in the Journal of the National Cancer Institute.
Bowles and her colleagues evaluated 12,500 women diagnosed with invasive breast cancer from 1999 through 2007 in eight different health systems. The patients' average age was 60. The follow-up time ranged from more than two years to nearly seven.
The researchers used data from medical records and other sources to track type of cancer treatment and diagnoses of cardiac problems.
The risk of heart failure was 1.4 times higher in those treated only with an anthracycline at the five-year mark. That was about the same increase as those treated with other types of cancer drugs. However, those on Herceptin alone had more than four times the risk of heart problems compared to those who did not take the medication, the study stated.
And, the biggest increase in risk was seen in those on both anthracyclines and Herceptin. Those patients showed a sevenfold increased risk at the five-year mark, the researchers said.
The increased risk reported in clinical trials has been 2 percent with anthracyclines and 4 percent with anthracyclines and Herceptin.
"These drugs are important to take [if needed]," Bowles stressed. "They improve survival."
However, she said, "women and providers need to be aware of the risk and what can be done to monitor [it]."
Dr. Joanne Mortimer, director of Women's Cancers Program at the City of Hope Comprehensive Cancer Center in Duarte, Calif., said the study does give some "real-world" perspective, said
"We know that Herceptin and Adriamycin [an anthracycline] are associated with an increased risk of heart problems," Mortimer said. "We know that any exposure to Adriamycin increases your risk of heart failure in later years, especially in older women."
"Heart problems that occur on Adriamycin do not usually improve when you stop the drug, whereas changes in heart functioning with Herceptin often reverse when you stop Herceptin," she said. "The fact that the risk of these heart problems continues long after the Herceptin is stopped [as the new study found] is sobering."
Monitoring may help.
"The early effects of these drugs on the heart can sometimes be picked up on testing before they are felt by the patient as symptoms of heart failure," said study co-author Dr. Larry Allen, an assistant professor of medicine at the University of Colorado Anschutz Medical Center, in Aurora.
"Therefore, women exposed to these drugs are often asked to do a pre-therapy test of heart function followed by intermittent testing during [and sometimes after] chemotherapy," he said.
Typically, Allen said, a doctor measures the heart's left ventricular ejection fraction (LVEF), a test of how well the heart pumps with each beat. There are many ways to measure it. Often an echocardiogram, which uses sound waves to evaluate the heart, is done.
The cost for this varies greatly, from $150 to much more, and insurance coverage varies.
It's not clear, Allen said, why the drugs affect heart function.
"The mechanism by which different chemotherapies impair and damage the heart vary widely," he said, "and, in some cases, are not completely understood."
Women need to understand the benefits and risks of any treatment, said Ann Geiger, an associate professor of public health sciences at Wake Forest Baptist Medical Center, and author of an editorial that accompanied the study. "The study suggests the long-term risk for heart failure may be higher in women treated in the community than in clinical trials, particularly women who are older and/or have [other diseases besides the cancer]."
To learn more about heart monitoring tests, visit the Cleveland Clinic.
Posted: August 2012
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