Children who are treated for cancer with anthracyclines should have their heart function monitored for the rest of their lives, Dutch researchers say. That's because the damage the chemotherapy can do to the heart appears to get worse over time, they report in the Annals of Oncology.

The study was led by Inge Brouwer of the pediatric oncology department of the University Medical Center in Groningen, the Netherlands. It involved 22 long-term survivors of bone cancer who were treated with doxorubicin (sold as Adriamycin, Doxil, and Rubex) between 1977 and 1990. Doxorubicin is commonly used against childhood cancers, leukemia, lymphoma, and other tumors.

It is well-known that doxorubicin can cause heart damage; about 5% of people who get the drug develop heart failure, Brouwer said. But she and her colleagues wondered if survivors might also have other, less obvious heart problems, and how those problems might develop and change over time.

To find out, the team checked the survivors' heart function about 9 years after treatment, again around 14 years after treatment, and finally about 22 years after treatment. The number of patients who had heart problems increased in that time span.

At the 14-year mark, just 2 survivors were found to have decreased systolic function, but by 22 years out, 6 patients had developed this problem. Systolic function measures how well the heart pumps blood. The researchers also looked at diastolic function, or how well the heart relaxes after pumping. Just 4 survivors showed problems in this area at the 14-year point, but 11 had a problem at 22 years. Most of the survivors also had a problem with their heart rate that could be a sign of future, more serious heart issues.

Only one of these patients though, had symptoms of heart failure such as shortness of breath or leg swelling.

The heart problems didn't appear to be related to how much doxorubicin the survivors had received during treatment. All had gotten high or moderate doses of the drug; none had received the lower doses that are often used to treat patients today. (Patients today can also be given drugs to protect their heart which were not available when the people in this study were treated.)The researchers also didn't find any differences according to the age of the survivors at diagnosis, or their current age (27-59 at the time of the final analysis).

The findings are important, Brouwer said, because no other studies have followed survivors for such a long time. That may be why these results differ from those of previous, shorter studies that didn't find worsening heart damage.

They're also important because they point out a silent threat many childhood cancer survivors may not know about. Brouwer said doctors need to be looking for heart problems, even if none are suspected, and be ready to take action.

"We need to keep checking [survivors] and be ready to start medication to stabilize their heart function in order to prevent further cardiac deterioration and development of cardiac complaints," she said in a statement. "It is important to be ready to treat cardiovascular risk factors -- for example, high blood pressure or cholesterol -- and to encourage patients to make helpful lifestyle changes such as stopping smoking, reducing their weight if necessary, and taking exercise."

Citation: "Long-term cardiac follow-up in survivors of a malignant bone tumour." Published online July 20, 2006, in the Annals of Oncology. First author: C.A.J. Brouwer, University of Groningen, Netherlands.