Another FDA-approved targeted cancer drug, sunitinib (SutentTM, Pfizer), may be linked to cardiac toxicity, report scientists at Childrens Hospital Boston, Dana-Farber Cancer Institute (Boston), and Thomas Jefferson University (Philadelphia). Their collaborative study, led by Ming Hui Chen, MD, MMSc, a heart specialist at Childrens who specializes in the cardiac health of cancer patients, appears in the December 15 issue of The Lancet, accompanied by an editorial.

Sunitinib is one of several new smart cancer drugs called tyrosine kinase inhibitors that targets specific signaling molecules inside cancer cells that aid cancer spread. Another targeted cancer treatment, imatinib (GleevecTM, Novartis Pharmaceuticals), was reported last year in Nature Medicine to be linked to heart failure in patients with chronic myelogenous leukemia.

Sunitinib was originally believed to be relatively free of cardiac side effects. However, a new retrospective analysis, focused on cardiovascular events, revealed a risk for heart failure, myocardial infarction and high blood pressure in 75 adult patients with imatinib-resistant, gastrointestinal stromal tumor (GIST) receiving multiple cycles of sunitinib in a phase I/II trial at Dana-Farber.

Of the 75, six (8 percent) developed symptoms consistent with moderate-to-severe congestive heart failure, and two had heart attacks. In all, eight (11 percent) had some kind of cardiovascular event while receiving sunitinib at FDA-approved or lower doses. Patients with preexisting coronary artery disease were more likely to develop cardiac problems. Nineteen percent of the 36 patients receiving the FDA-approved dose had decreases in left ventricular ejection fraction, a measure of the hearts pumping ability.

In addition, 47 percent (35 of 75) developed hypertension. High blood pressure is a common side effect with certain cancer drugs, but the degree of high blood pressure both the percentage of affected patients and the magnitude of increase in systolic blood-pressure was notable, says Chen, who is also affiliated with Brigham and Womens Hospital, Dana-Farber Cancer Institute and Harvard Medical School.

Two patient biopsies revealed abnormalities in the heart cells mitochondria (the structures responsible for energy production). Further studies, led by Maria Rupnick, MD, of the Childrens Hospital Boston Vascular Biology Program, and Thomas Force, MD, from the Center for Translational Medicine and Division of Cardiology at Jefferson, examined heart-muscle cells from mice who had received the equivalent of a human dosage of sunitinib alone, and found direct evidence of cardiotoxicity.

Early identification of cardiac side effects is an important part of keeping patients on life-saving cancer treatment over the long-term, says Chen. In this study, the cardiac dysfunction and high blood pressure were commonly medically manageable. Most importantly, patients were most often able to resume sunitinib treatment following temporary withholding of drug, addition of cardiac medications and/or dose adjustment.

This sunitinib study highlights potential concerns with agents that are multi-targeted, meaning they inhibit multiple factors involved in cancer progression, adds Force, who led the study of imatinib patients published in Nature Medicine last year. Some of these factors may also play important roles in maintenance of proper heart function, and their inhibition by cancer drugs could have adverse effects on the heart.

The most important element of this new work is the close, creative collaboration between our medical oncology and cardiology teams, says George Demetri, MD, a co-author on the paper and director of the Ludwig Center at Dana-Farber Cancer Institute and Harvard Medical School. As our molecular targeting involves more pathways, we can inform one anothers fields and identify side effects early by working together across traditional disciplinary boundaries.

We are hopeful, Chen concludes, that this type of multidisciplinary approach, from the patients bedside to the basic cell biology laboratory, will lead to further pharmaceutical advances that will make these smart cancer drugs even smarter.

Childrens has a long history of researching the cardiovascular effects of cancer drugs. In children, such side effects are particularly important to manage so they can survive the cancer in good health well into adulthood. In 1991, for example, Childrens heart specialists published the seminal finding that doxorubicin treatment for childhood leukemia can lead to clinically important heart disease.


Posted by: Jessica    Source

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