It's not just that the PSA didn't go down along with tumor and bone responses, it's that it actually skyrocketed (typically doubled or more). In all other prostate treatments I am aware of (except for Dendreon's) PSA was tightly linked to improvement.
I have no idea what this means, but I'll take actual improvement in tumors, mets and pain over a biomarker any day.
I'm not impressed with the prostate portion of this trial at all. What does look promising is the bone lesion section which possibly could be used in many cancer types. Exel's results look promising compared to the new kid on the block Amgen in this indication.
Denosumab delayed prostate cancer's spread to the bones by 4.2 months compared to Excel's actually reducing or eliminating the bones mets. While there needs to be many more larger trials, when I see that 46% of the patient population stopped taking narcotics for their bone pain tells me something is happening.