This is an accelerated approval - unlike provenge - it would be easy for FDA to pull the approval if OS is not significant.
Of course if FDA really cared for the OS endpoint, it should have never allowed it to be submitted first.
My reason for being long:
1. The The rumor that OS was harmed turned out to be false.
2. FDA stats criticism about PFS was regarding the inclusion of stuff other than radiological progression, however, the sensitivity analysis (although informative censoring) which stripped off non-radiological events confirmed the primary analysis.
3. Pain progression data, although unconventional, did provide tangible measurement of patient benefit, which is crucial for an AA based on surrogate endpoint.
4. Like Walldiver said, this is a dog and pony show to set a counter example to DORB and DNDN. There is no mechanism of action issue, there is no alpha error issue, and Maha - the quartile lady would be more than pleased to learn there is no "beta error" issue, and it is a large study.
5. I like how the company rationalized Single-trial approval strategy - they must have copied it from the DNDN IV board.