That Happened!

New York - According to a study published by a university research team in the Journal of the American Medical Association, Genentech’s cancer drug Avastin significantly ups the risk of blood clotting in patients.

The biotech giant disputes the findings of the report.

Avastin, an angiogenesis inhibitor, works to block the ability of the protein VEGF (vascular endothelial growth factor), to provide a blood supply to cancerous tumors. Used in tandem with chemotherapy, Avastin helps to improve the prognosis of certain patients with lung or colon cancer.

Headed by Dr. Shenhong Wu of the Stonybrook University Cancer Center in Stonybrook, N.Y., the study involved the analysis of 8,000 patients in 15 separate clinical trials. The results indicate that the use of Avastin increased the risk of blood clots in the arteries of chemotherapy patients by a significant 33%.

Arterial blood clots pose a serious health threat; clots that break off may become lodged in the lungs and cause a fatal pulmonary embolism. Symptoms of a blood clot include shortness of breath, leg pain, and edema (swelling). According to Dr. Gary Lyman of Duke University, blood clots are not uncommon in cancer patients in general; oncologists typically use blood thinners to reduce the risk of a pulmonary embolism.

Genentech researchers disagree with Dr. Wu’s findings, citing a 2007 analysis of 5 separate trials that revealed only a slightly increased risk of blood clots with the use of Avastin. Genentech’s head of clinical development for Avastin, Dr. Philippe Bishop, states that the results of Dr. Wu’s study could have been slanted by several factors, such as the different methods used to report data in each of the 15 trials.

Dr. Bishop acknowledges that there has been evidence of an elevated risk of clotting with Avastin, and points out that drug warnings to that effect have been issued to the medical community. He disagrees, however, that the increased risk could be as high as 33%.

The findings of Dr. Wu’s study, as he emphasizes himself, should not be a reason to avoid the use of Avastin. He stresses only that patients taking the drug, along with their doctors, should be aware of the risks and remain on the alert for symptoms of an arterial blood clot. He agrees with Dr. Bishop that a larger-scale study is needed to uncover other possible causes of clotting in patients who take Avastin.

Treating cancer is a complex problem, and doctors must carefully weigh the benefits of any particular treatment against the risks to their patients’ health on a case-by-case basis. Dr. Wu reasons that his findings warrant that the risk of clotting should be included in the “black box” warning (the FDA’s highest alert) on the label of Avastin.