Washington ? A successful cancer-fighting drug may also damage the heart, although a researcher says leukemia patients who need Gleevec should not abandon it.

While effectively treating cancer, Gleevec can lead to heart failure in some patients, said Dr. Thomas Force, who teaches medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia.

His study, published Sunday in the online edition of the journal Nature Medicine, was prompted by reports that 10 patients taking Gleevec for chronic myelogenous leukemia developed severe congestive heart failure.

Gleevec, sold under the Glivec in some countries, had worldwide sales of $1.2 billion in the first six months of this year, according to the manufacturer, Novartis Pharmaceuticals Corp.

Force said he is trying to call attention to the fact that Gleevec and other similar drugs coming along could have significant effects on the heart and that doctors need to be aware of this and watch for symptoms. These patients can be helped with heart treatment, he said.