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The drug was approved for advanced kidney cancer and a rare form of gastrointestinal cancer.
"Our data support a role for routine cardiac monitoring for patients receiving sunitinib [Sutent] and careful study of adverse cardiac events in future studies," said study author Dr. Melinda Telli, a postdoctoral fellow in medical oncology at Stanford University School of Medicine. "This is especially important, because sunitinib is being investigated in over 30 different tumor types for advanced as well as early forms of cancer. Determining what factors put patients at increased risk will allow us to administer this medication more safely for patients whose benefits clearly outweigh the risks."
Telli was to present the findings at the 2008 Genitourinary Cancers Symposium in San Francisco. She spoke to reporters at a Tuesday teleconference.
Other experts agreed that monitoring of patients on Sutent is advisable, but they also cautioned that there is still little reason for alarm.
"This is a small study and one that makes us want to look further into it . . . but this is not a crystal clear characterization of injury," said Dr. Patrick Lowry, an assistant professor of surgery at Texas A&M Health Science Center College of Medicine and section head of laparoscopy and endourology at Scott & White Memorial Hospital in Temple.
"At the same time, this certainly is more patients with heart failure than they saw with the initial studies," Lowry said. "Perhaps, as they suggested, we need to follow patients a little bit closer from a cardiac standpoint."
And, Lowry pointed out, patients being treated with Sutent often have incurable metastatic cancer. At that point, "we're just trying to improve and extend their life as long as we can, and there are going to be pluses and minuses to anything," he said.
The study -- which was funded by Sutent's maker, Pfizer -- looked at 48 patients in a "real-world" setting who were taking the drug for either advanced kidney cancer or a gastrointestinal stromal tumor (GIST).
Fifteen percent of the patients experienced heart conditions such as symptomatic left ventricular dysfunction or heart failure while taking Sutent. The problems began between 22 days and 435 days after beginning therapy, although most started within the first three months of treatment.
The 15 percent incidence of heart trouble shown in this setting is almost double that seen in clinical trials, which had found that up to 8 percent of patients had experienced heart failure.
Heart failure involves a decline in the heart's ability to pump blood.
In this study, individuals with a history of heart failure, coronary artery disease or low body-mass index were at an even higher risk if they took Sutent, the researchers noted.
Three of five patients followed long term continued to have heart problems even after they stopped taking the drug.
Two recent studies, one published in January in the New England Journal of Medicine and another in December in The Lancet, also found that use of Sutent can boost patients' blood pressure and add to their risk of heart failure.
At the time of the release of The Lancet paper, Pfizer released a statement agreeing that these heart risks do exist. However, the company added that the cardiovascular events "were medically manageable in most patients and underscore the importance of having a collaborative team of health-care professionals working together to appropriately manage patients who have limited available options" in treating their cancer.
A second study, also being presented at the conference, found that a procedure known as partial nephrectomy is being underutilized in treating patients with small kidney tumors.
Partial nephrectomy involves removing only the part of the kidney bearing the tumor, while radical nephrectomy involves removing the whole kidney.
"Radical nephrectomy has essentially been the gold standard since the 1940s and 1950s," said study author Dr. William Huang, an assistant professor of urologic oncology at New York University School of Medicine. "There is a greater than 90 percent cure rate, but the procedure does increase the risk of going on to develop chronic kidney disease."
Partial nephrectomy appears to be equally effective in tumors less than 4 centimeters and even in some up to 7 centimeters in size. Although there are potential complications here as well, partial nephrectomy does a better job of preserving kidney function and preventing chronic kidney disease.
Huang and his colleagues found that women, older patients and patients with cerebrovascular disease such as stroke were more likely to have the entire kidney removed. Only 20.5 percent of men and 22.4 percent of patients aged 66 to 69 had the partial procedure, versus 16 percent of women and 7.1 percent of patients aged 85 and over.
"Most of the newly diagnosed kidney tumors are amenable to partial nephrectomy but in those newly diagnosed, many continue to undergo radical nephrectomy," Huang said. "Partial nephrectomy is an option for most patients with newly diagnosed tumors and may be a better option, because people with kidney tumors may have other conditions."
SOURCES: Patrick Lowry, M.D., assistant professor, surgery, Texas A&M Health Science Center College of Medicine, and section head, laparoscopy and endourology, Scott & White Memorial Hospital, Temple, Texas; Feb. 12, 2008, teleconference with Melinda Telli, M.D., postdoctoral fellow, medical oncology, Stanford University School of Medicine, and William Huang, M.D., assistant professor, urologic oncology, New York University School of Medicine
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