Investors in Dendreon (Nasdaq: DNDN) and Cell Genesys (Nasdaq: CEGE) who were hoping their companies would have the world's first approved cancer vaccine are going to have to duke it out for the U.S. title. Yesterday, Antigenics (Nasdaq: AGEN) claimed the world title with the Russian approval of its kidney cancer vaccine, Oncophage.

This isn't a vaccine in the traditional sense -- it doesn't keep patients from getting cancer. Cancer vaccines induce the patient's immune system to attack the tumor after the patient has already been afflicted with cancer.

There's apparently a very simple reason that Antigenics went to Russia to gain approval for Oncophage: There's no way that the U.S. would approve the treatment given its current data. Its phase 3 trial failed to show that Oncophage could slow down the recurrence of kidney cancer after surgery.

The company reanalyzed the data and found that a subset of patients -- those who have lower-stage tumors and thus a better prognosis of survival without treatment -- responded well to the drug. Oncophage improved the chance of cancer not recurring in this subset of patients by 45%.

However, the FDA doesn't accept subset analyses for support of marketing applications. Such analysis is just an observation, not actually testing of a hypothesis. Of course, the company's observation could become a testable hypothesis. If Oncophage were to be tested in just these better-prognosis subjects in another trial, it could lead to FDA approval. Instead, Antigenics decided to try to get the drug approved in Russia and, possibly, the European Union.

Whether they have a different scientific method in Russia or they're just willing to take a flier on an unproven treatment, I don't know. Either way, Antigenics plans to begin selling the drug starting in the second half of this year.

Hopefully, it'll be able to use the money it makes off treatments in Russia and fund another trial. Until then, U.S. kidney cancer patients will just have to stick with proven conventional treatments like Pfizer's (NYSE: PFE) Sutent and Onyx Pharmaceuticals' (Nasdaq: ONXX) Nexavar. Or fly to Moscow for the unproven stuff.

Get treated to some more oncology-focused Foolishness:

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Fool contributor Brian Orelli, Ph.D., likes to talk about the scientific method at parties. He doesn't own shares of any company mentioned in this article. Pfizer is a pick of both the Income Investor and the Inside Value newsletters. The Fool's disclosure policy avoids Brian at parties.