UPDATE 1-Avastin raises risk of blood clots in veins-study
(Embargoed for release at 4 p.m. EST/2100 GMT) (Adds details, background; byline)
CHICAGO, Nov 18 (Reuters) - The popular cancer drug Avastin raises the risk of blood clots in the veins by a third when added to chemotherapy, U.S. researchers said on Tuesday.
An analysis of 15 clinical trials involving nearly 8,000 people found Avastin, marketed by Roche (ROG.VX) and Genentech DNA.N, raises the risk of a blood clot in the veins from about 10 percent of patients to about 13 percent.
The study shows "a significant increased risk with Avastin for patients while they are taking chemotherapy," said Dr. Shenhong Wu of Stony Brook University Cancer Center in New York, whose study appears in the Journal of the American Medical Association.
Wu said the findings should not dissuade cancer patients from taking the drug. Instead, doctors and patients need to be on the lookout for signs of blood clots.
Many cancer patients already have an elevated risk of blood clots in the body's veins, known as venous thromboembolism. These clots can break off and travel through the bloodstream, potentially blocking blood flow to the lungs.
"These patients are at high risk for venous thromboembolism even without Avastin. On top of that, Avastin increased the risk by about 33 percent," Wu said in a telephone interview.
"In 100 patients, if they get chemotherapy about 10 many develop blood clots. With Avastin, about 13 patients will develop blood clots," he said.
Avastin, known generically as bevacizumab, is a monoclonal antibody, a genetically engineered immune system molecule that targets vascular endothelial growth factor or VEGF. VEGF helps tumors grow a blood supply and Avastin is a so-called angiogenesis inhibitor that helps choke off that supply.
KNOWN ARTERY RISK
The Avastin label already carries a warning about blood clots in the arteries, which could break loose, travel through the arteries and cause strokes and heart attacks.
It also notes that some people taking Avastin and chemotherapy have had blood clots in the veins.
"It's not a new safety signal for Avastin. The risk is referenced in the adverse reaction section of the label," said Charlotte Arnold, a spokeswoman for Genentech.
Wu said the study attempts to clarify the risk for blood clots in the veins, where studies have been inconsistent. He said it is important patients are fully informed of the risks.
Dr. Gary Lyman of Duke University, who chaired a panel for the American Society of Clinical Oncology that set guidelines on managing blood clots in cancer patients, said the overall risk is fairly small. Continued...
