Fans of biotech bigwig Genentech ( DNA) are hoping big sales of Avastin and Lucentis will carry the day as the company reports fourth-quarter results after the close.

Analysts say Avastin, the company's highly touted colorectal cancer drug, could see a boost from strong sales growth as a nonsmall-cell lung cancer treatment.

"Avastin use in nonsmall-cell lung cancer is on pace to grow quarter over quarter by over 50% vs. our prior estimate of 25%," says Rodman & Renshaw analyst Michael King.

In October, Avastin received a new Food and Drug Administration approval as a first-choice treatment for nonsmall-cell lung cancer in a combination with chemotherapy drugs. Based on recent cancer treatment regimens and sales trends noted by drug market research firm IMS Health, King raised his Avastin sales estimates to $485 million from the $465 million he previously expected.

King says sales of Genentech's eye drug Lucentis could blow past consensus estimates of $152 million, reaching $204 million. The analyst previously expected Lucentis sales of $169 million, and says results could still exceed his higher target.

Even before its launch in the third quarter, Lucentis was touted by researchers as the most effective treatment for macular degeneration. Unlike its competitors -- Visudyne sold by Novartis ( NVS) and Macugen from OSI Pharmaceuticals ( OSIP) -- Lucentis not only slowed or stopped vision loss, it actually improved vision in a number of patients.

But some observers worry that Genentech's performance on other fronts may drag down the overall numbers.

One weak spot on sales could be Genentech's rheumatoid arthritis drug Rituxan. With fewer new patients receiving the drug, sales were soft in the third quarter and growth could continue to slow. Meanwhile, sales of cancer drug Tarceva, which has been overshadowed by Avastin, are also expected to be flat.

However, says Miller Tabak analyst Les Funtleyder, "I think so-so Tarceva sales and possible Rituxan sales are more or less priced into the stock."

Leerink Swann analyst William Tanner is less optimistic than his colleagues. He expects Genentech to earn 51 cents a share, 4 cents short of consensus estimates excluding stock options expenses. He sees fourth-quarter revenue of $2.5 billion vs. consensus estimates of $2.54 billion and the $2.66 billion expected by Jefferies & Co. analyst Adam Walsh.

But while Rituxan "is still a question mark," according to King, at least its sales shouldn't take a hit yet from recent safety concerns, says Leerink's Tanner. In December, Genentech said a number of lupus patients had an increased risk of developing the same rare brain disease that led to Biogen Idec's ( BIIB) Tysabri being pulled off the market in 2005.

King expects the fourth-quarter sales of Rituxan to reach $528 million, short of the $541 million consensus estimate. Rituxan is jointly marketed by Genentech and Biogen Idec.

A year ago , Genentech's shares dropped after the company met, but didn't exceed, its fourth-quarter estimates. But if recent hopes have fallen with the company's share price, which sank more than 12% in 2006, the post-earnings move this time may not be as severe.