Stretching out a dose of chemotherapy over six or more hours may reduce the risk of heart problems caused by certain commonly used cancer drugs, according to a new review of recent research.

Anthracycline drugs like daunorubicin and doxorubicin are used to treat many types of solid tumors and blood cancers such as leukemias in adults and children.

Anthracycline therapy can be very successful at controlling cancer, but heart damage caused by anthracycline treatment “is a considerable and serious problem,” said Dr. Elvira van Dalen of the Emma Children’s Hospital in the Netherlands.

She and her colleagues found that the rates of heart failure among adult patients receiving anthracycline therapy were significantly lower when the patients had an infusion of the drug that lasted six or more hours, compared to shorter infusions times.

In five studies involving 557 patients, the longer treatment cut the risk of heart failure by nearly 75 percent compared to the risk in patients who received the short treatment.

van Dalen said the prolonged dose of six hours or more “might be justified” if a patient is at high risk of heart damage or needs a high cumulative dose of the chemotherapy.

The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

In some of the studies, the prolonged dose also reduced the risk of less severe problems such as weakened heart function. Patients had the same chance of survival and tumor shrinkage whether they received the long or short therapies, the Cochrane researchers found.

“It should be emphasized that the majority of the patients included in these studies were adults with advanced solid tumors,” van Dalen and colleagues said, noting that there are few good studies about the length of anthracycline treatment in children.

Among the children in the study, there was no difference in heart damage between the long and short treatments “and no information on survival and tumor shrinkage was available,” van Dalen said.

Recent studies have shown that the toxic heart effects of anthracycline therapy can have lasting effects on children’s health. Dr. Stephen Lipshulz, a pediatric cancer specialist at the University of Miami, said childhood cancer survivors “may be at significant risk of serious cardiovascular problems at a much younger age,” than researchers believed a few years ago.

Lipshulz’s work suggests many childhood cancer survivors suffer from enlarged hearts and prematurely hardened arteries, due at least in part from their chemotherapy. “It’s alarming that we’ve found such dramatic heart damage and blood vessel risk in some survivors who are just 10 or 15 years from treatment,” he said.

van Dalen EC, et al. Different dosage schedules for reducing cardiotoxicity in cancer patients receiving anthracycline chemotherapy. The Cochrane Database of Systematic Reviews 2006, Issue 4.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.