Now that Genentech ( DNA) has a strong third-quarter earnings report behind it, investors are turning their attention to a possible buyout by Swiss drugmaker Roche and a large clinical trial of cancer treatment Avastin that could add billions of dollars in sales to the drug's already blockbuster status. Several interim analyses of the phase III study, which is testing Avastin as an adjuvant therapy in patients with colon cancer, have been conducted already. None have resulted in strong enough data to stop the study. The next scheduled examination of the data will occur this quarter, Sue Desmond-Hellmann, Genentech's president of product development, said Tuesday. At that point, Genentech will determine whether to release the results or indicate instead that the trial will proceed. If the findings this quarter aren't unequivocally in Avastin's favor, the review will continue to a final analysis, currently expected in mid-2009, according to the company. Adjuvant cancer therapy involves treating patients with drugs (or radiation or hormones, in some cases) soon after surgery in which the patient's primary tumor is removed. The idea is to kill any residual cancer cells that surgery may have missed and, by doing so, lower the risk that the cancer will return. Right now, Avastin is approved as a treatment for patients with colon, lung and breast cancers. U.S. sales totaled $2.3 billion in 2007 and almost $2 billion through the first nine months of this year. But adjuvant use of Avastin in patients undergoing successful colon cancer resection surgery could tack on another $5 billion in sales, according to one estimate from the analysts at Cowen & Co.