As of of April, the median survival for the even smaller hi dose GVAX subgroup that received subsequent docetaxel was >35.2 months and had not been reached.The Vital-1 control arm is docetaxel which in the TAX 327 Ph 3 trial reported median survival of 22 to 23 months in asymptomatic AIPC. If the number of events required for the interim is 200 and the allocated alpha p value for the interim is 0.01, what are the chances that Vital-1 will be statistically significant?
Placebo median of 22.5 months and treated median of 36 months if representative of the true efficacy is probably an HR>=2.0 (depends on curve shapes to really pin it down). And with 200 events that is probably a power in the 97 to 99 percent class.
What if the median survival is only 30 months?
Again, it depends on details like curve shape etc, but I'd guess it to be in the 90-95 percent powered class.
Given that almost no one actually powers their trials at 99.9 percent (which is what that implies for, say, 400 events at completion) I'd bet VERY confidently that CEGE doesn't actually believe that their HR is that high.
