After a couple of disappointing trials for Pfizer's (NYSE:PFE) Sutent, it was nice for investors to get some good news about the drug -- even when everyone already knew what it would be.

Earlier this year, an independent data monitoring board ended a trial testing Sutent against pancreatic islet cell tumors, a type of pancreatic cancer, because the drug was working better than placebo. When a drug is clearly working, trials are ended so that patients who are taking the placebo can be switched over to the effective drug, but the actual results are often saved for a scientific meeting.

Today investors got to see how effective Sutent really is against pancreatic islet cell tumors. The median time for progression of disease was more than double for patients taking Sutent compared to those taking placebo. That's pretty darn impressive.

The nice thing about expanding labels for drugs -- Sutent is already approved to treat two other kinds of cancer -- is that companies don't have to wait for approval to see an uptick in sales. Given the few treatment options for pancreatic islet cell tumors, doctors are likely to prescribe it off label before the drug is approved for that use. In fact, the company's presentation of the data at the World Congress on Gastrointestinal Cancer acts as a perfectly legal way to promote the use of the drug.

Sutent could use a little push to get sales growth back in gear; after growing sales 166% from 2006 to 2007 and 46% the following year, sales were up just 7% year over year in the first quarter of this year. Tough competition from Onyx Pharmaceuticals' (NASDAQ:ONXX) Nexavar and Wyeth's (NYSE:WYE) Torisel in kidney cancer, and the fact that Sutent is only recommended after Novartis' (NYSE:NVS) Gleevec in gastrointestinal stromal tumors -- cancer of the digestive system -- mean Pfizer is going to have to look elsewhere for sales growth.

Pfizer might not find too many additional sales expanding into pancreatic islet cell tumors, though. The type of pancreatic cancer is fairly rare -- there might be just 600 to 1,200 patients diagnosed with it each year in the U.S. -- but there has been at least one famous sufferer: Steve Jobs of Apple (NASDAQ:AAPL). The expansion into pancreatic cancer will add a little to the sales figure, but large growth will need to come from Pfizer showing that Sutent works in tumors with larger markets like breast and lung cancer.

Investors in Pfizer are going to need to remain patient. It's going to take time to work through the merger with Wyeth and it'll take a while before Sutent becomes the multibillion blockbuster it's capable of becoming.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.