With biotech, the devil is often in the details. So investors have been anxiously awaiting the release of data from Onyx Pharmaceuticals' (NASDAQ:ONXX) phase 2 trial testing Nexavar against breast cancer -- though you couldn't tell that from today's stock-price movement.

Onyx and marketing partner Bayer said in July that Nexavar passed the trial, but there's a big difference between knowing the drug performed statistically better than placebo and knowing how much better it performed -- especially in a crowded breast-cancer market.

But it doesn't look as though investors had much to worry about, after all. Nexavar, when taken with Roche's Xeloda, extended the time it took for tumors to start growing again by an additional 2.3 months compared with using Xeloda alone.

Because it's being combined with another drug, Nexavar doesn't have to show an overwhelming improvement to get approved. It's the same strategy that Pfizer (NYSE:PFE) is using to test Sutent in breast cancer. Of course, this approach doesn't always work: sanofi-aventis (NYSE:SNY) and Regeneron Pharmaceuticals (NASDAQ:REGN) stopped a trial last week because it didn't appear that their oncology drug in combination with Eli Lilly's (NYSE:LLY) Gemzar was working any better than Gemzar alone.

The solid data is great news for Onyx, which doesn't have much else going for it in the near term except expanding Nexavar into additional cancers. Breast cancer is a much larger market than the liver- and kidney-cancer markets that Nexavar is currently approved for. It's not unreasonable to expect sales to double from here if Nexavar is approved to treat breast cancer.

While the data looks good, Nexavar still has to perform in a phase 3 trial to get approved. Fortunately, investors should have an even better idea of how it'll perform in a larger trial after Onyx and Bayer release data from three other ongoing phase 2 trials.