New Cancer Drug Tied to Heart Problems

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The researchers looked back at the medical records of these patients, noting those who died from heart disease or had suffered heart attacks or congestive heart failure. They also looked at the effect of sunitinib on the heart's ability to pump blood and on blood pressure.

Chen's group found that eight patients given repeated cycles of sunitinib had cardiovascular events. Two had heart attacks, and six had heart failure. Of 36 patients given the approved dose of sunitinib, 10 had a 10 percent or more reduction in the ability of their heart to pump blood, and seven had a 15 percent or more reduction in heart function.

In addition, sunitinib was associated with increases in blood pressure, with a total of 35 (47 percent) of the patients developing hypertension. However, these effects were not permanent: When sunitinib treatment was stopped and patients began therapy to ease heart problems, levels of heart failure and heart functioning improved, the researchers found.

"Most of the patients who had heart problems were able to resume taking sunitinib with either a modification in their dose or initiation of heart failure medication," Chen said.

In addition, in experiments with mice and rat heart cells, Chen's team found that sunitinib triggered heart cells damage and death.

However, in their statement, Pfizer noted that, "Lower incidences of cardiovascular effects have been observed in subsequent randomized Phase 3 prospective Sutent studies in both renal cell carcinoma and gastrointestinal stromal tumor[s]." That includes a lower incidence of events such as congestive heart failure, impaired heart function, and high blood pressure that were noted in Chen's retrospective analysis, the company said.

Chen stressed that patients taking sunitinib who develop shortness of breath and fatigue and swelling of the arms or legs should be checked for heart problems. "These symptoms can be ascribed to cancer, but since this drug may have a cardiovascular effect, these may be signs of heart problems," she said.