Dendreon's Got Miles to Go With Provenge

Let's say you're running in the Olympic marathon and you're in the lead. You're about to enter the Olympic stadium to run the last quarter mile, and the guy in second place is still on the road at mile 24. Your gold medal is guaranteed, right?

Yes, if this marathon were a typical race. But this marathon is being run under different rules. To win, you not only need to cross the finish line first, but you also have to beat the guy in second place by 12 minutes. If the guy behind you can run the last two miles in under 12 minutes, he wins the race, not you.

Under these rules, your place on the gold medal podium is far from assured.

The bio-statistics of the Provenge study are a lot like this far-fetched marathon example. By all outward appearances, Provenge looks close to the finish line. The cancer vaccine only has to lower the risk of death by another 2% to declare victory.

But to get that last 2% survival benefit, the surviving Provenge patients in the study must live longer than those who have died already (and were therefore counted in the interim analysis).

Unfortunately, many of these latter Provenge patients are in much worse condition (they have more advanced prostate cancer) than those who came before them because Dendreon loosened the entry criteria of the study in midcourse to accelerate enrollment. The interim analysis was also probably performed with well over half the deaths of the study already recorded (perhaps as many as two-thirds), which means that there are fewer patients left alive to significantly accelerate the survival benefit.