Zytiga Then Xtandi or Xtandi Then Zytiga?

You have become castrate resistant and already have taken Provenge.  Now, what treatment should be next?  Currently, the two best options are either Zytiga (abiraterone) or Xtandi (enzalutamide).  Which should come first?

They both are FDA approved for this stage of advanced prostate cancer, they are both hormonal therapies, but their modes of action are different.  Zytiga blocks the production of androgens and Xtandi blocks the androgens being produced from interacting with the cancer cells. 

This decision is probably the most perplexing question faced by men with advanced prostate cancer at this juncture of their cancer.  Which drug to take first, Zytiga (abiraterone) or Xtandi (enzalutamide)? 

In a recent retrospective study looking at data from 198 men at Kyoto University Hospital in Kyoto, Japan and at the Johns Hopkins Cancer Center in Baltimore, MD this question was researched.

The researchers at these two institutions compared both the progression-free survival and overall survival (OS) between men who first took Zytiga then moved on, at disease progression, to Xtandi to a group of men who first took Xtandi then, on disease progression, moved on to Zytiga. 

They concluded that the men who first used Zytiga have a slightly longer progression-free survival on the abiraterone-enzalutamide sequence than on the enzalutamide-abiraterone sequence, but the actual sequence will have little to no impact on a man’s overall survival.

The total murkiness of this finding indicates that this decision might best depend upon the patient and the type of prostate cancer they are fighting. This lack of clarity provides us with one of those situations where the experience of a very competent medical oncologist can offer the best guidance.   

To really get the right answer will require a comprehensive controlled clinical trial.  Until this type of trial is conducted, we will need to continue to fly by the seat of our pants.



Joel T. Nowak, MA, MSW wrote this Post.  Joel is the CEO/Executive Director of Cancer ABCs.  He is a Cancer Thriver diagnosed with five primary cancers - Thyroid, Metastatic Prostate, Renal, Melanoma, and the rare cancer Appendiceal cancer.