UPDATE 1-Pfizer cancer drug Sutent linked with heart risks

(Adds Pfizer comment in paragraphs 18-19)

By Julie Steenhuysen

CHICAGO, Dec 13 (Reuters) - Pfizer Inc's (PFE.N: Quote, Profile, Research, Stock Buzz) cancer drug Sutent may have toxic effects on the heart, U.S. researchers said on Thursday.

Nearly half of 75 patients with rare gastrointestinal tumors who took the drug in a clinical trial developed high blood pressure, 8 percent developed heart failure and two patients had heart attacks, according to a new analysis of clinical trial data.

The analysis, conducted by researchers at Children's Hospital Boston, the Dana-Farber Cancer Institute in Boston and Thomas Jefferson University in Philadelphia, suggests patients taking the drug -- and especially those with heart risks -- should be closely monitored.

"If a patient develops shortness of breath, fatigue and swelling of the feet and hands, they should seek medical attention," said Dr. Ming Hui Chen, a cardiologist at Children's, whose study was published in the Lancet medical journal.

Most of the patients in the study responded to medications to control their symptoms, she said.

The finding follows the discovery last year that the Novartis AG (NOVN.VX: Quote, Profile, Research, Stock Buzz) drug Gleevec, a pill that transformed treatment for leukemia patients, caused heart failure in 10 patients.