Expected and extraordinary news today on the new treatment front. Medivation and Astellas’ Xtandi (enzalutamide) was approved for use in men with castrate resistant prostate cancer.

The new FDA approved label for Xtandi says that it is for the treatment of men with metastatic castration-resistant prostate cancer. This label is basically the same as for Zytiga. Both encompass the pre-chemo and post-chemo stages in castrate resistant prostate cancer. However, in the clinical section of the Xtandi label says that there is statistically significant improvement in overall survival when compared to Zytiga.

I must remind you that this seeming advantage to Xtandi comes from a statistical conundrum stemming from the way the Xtandi and Zytiga clinical trials were conducted. Zytiga never showed a statistical survival advantage because the trial was stopped early (before the data matured) as a result of the drug demonstrating so much promise that it was felt that it was unethical to continue the trial. We do not know and we will never know the statistical survival advantage that Zytiga might provide.

What is important and worthy of celebration is that Xtandi is now FDA approved in the pre-chemotherapy stage of castrate resistant prostate cancer. It joins Zytiga and Provenge in the pre-chemotherapy stage.

Approval Based on Improved Overall Survival, Delayed Time to Radiographic Progression and an Overall Positive Benefit-Risk Profile

Joel T. Nowak, M.A., M.S.W.