Genentech's Avastin: How Big Is The Risk?

Warning on risks of leading cancer drug sends Genentech shares down... Genentech and the U.S. Food and Drug Administration warned doctors on Friday that Genentech's colon cancer drug, Avastin, can increase the risk of blood clots in some patients, a condition that may lead to stroke or heart attack. This sent the stock down more than 6%, to 44.23. A company spokeswoman acknowledged that heart ailments had killed some patients who took the drug, and that additional trials data led to the "dear doctor" letter on August 12. But is this, as Jim Cramer of CNBC said, "much ado about nothing"?