The drug, doxorubicin, is used in the treatment of many cancers, from leukemia and breast tumors to lung and testicular cancers. The new research doesn't second-guess the therapy. However, experts say it should prompt cancer specialists to be especially vigilant about budding congestive heart failure, particularly in patients most vulnerable to the problem, such as children, the elderly and those who've had radiation therapy.
"What this paper has demonstrated is that while we thought we had a pretty good idea of exactly what the risks are of doxorubicin, we have to be a little more cautious" in using it, says study co-author Dr. Michael Ewer, a heart expert at the University of Texas' M.D. Anderson Cancer Center. "If you have signs of decreasing function then you do need to stop the drug right away, but that's usually a little later than you wished you would have stopped it."
A report on the findings appears in the June 1 issue of Cancer. The work was funded by Pharmacia, which makes a version of doxorubicin called Adriamycin.
Ewer's group, led by Dr. Sandra Swain of the National Cancer Institute, reviewed three earlier studies of doxorubicin, also known as Rubex, and heart failure in patients with lung and breast cancer. Of the 630 subjects, 32 were diagnosed with congestive heart failure.
The risk of the complication rose with the cumulative dose of the drug. Heart failure occurred in 1.7 percent of patients taking a low dose -- measured in milligrams per meters squared -- but it occurred in 26 percent of people on a moderate to high regimen. Nearly half of patients on the highest doses developed the condition.
The overall rate of heart failure in people on doxorubicin was roughly 5 percent at a medium dose, higher than the rate reported in the most recent study to examine the effect.
In addition to the greater prevalence of heart problems, Ewer's group noted two other areas of concern with the cancer drug. People over age 65 were about 20 percent more likely than younger patients to suffer the complication. And a heart output test doctors have been using to monitor heart function in people taking doxorubicin doesn't seem to be of much use. Some patients with no problems have abnormal test results, while others with failing pumps go undetected. "It's just an imperfect test," Ewer says.