Caution - Testosterone Flare During Transition from Degarelix to Leuprolide

Degarelix (Firmagon) is a newer hormone therapy drug (ADT) that is used to shut down the production of testicular testosterone.  It is used as an alternative drug to the older and less expensive drug Leuprolide (Lupron).

Degarelix is considered superior to Lupron for initiating ADT because it drops testosterone levels quicker than the alternative drugs and is not accompanied with a PSA flare that is common with the older synthetic gonadotropin-releasing hormone drugs like Lupron.

Because of its higher cost, Degarelix is sometimes used only to initial the ADT and is then replaced with Lupron, or a similarly acting drug.

Given this common practice of changing treatments, there was a study initiated to evaluate for a possible testosterone surge during a transition of therapy from degarelix to leuprolide (Lupron).  Researchers conducted a prospective, single-arm, open-label trial evaluating the possibility that there might be a PSA flare during the transition from Firmagon to Lupron. In this study, men were administered three (3) monthly depot injections of degarelix, followed by one 3-month depot injection of leuprolide.

The researchers considered a rise in serum testosterone to be clinically relevant in previously castrate men whose testosterone rose above 50 ng/dl.

At the conclusion of the study, there were forty-five men aged 59-86 years included in the final analysis.

They found that there were fluctuations in serum testosterone after the transition from degarelix to Lupron, but they characterized them as mild and short-lived with 8.9% of men experiencing testosterone elevations to non-castrate levels as defined by their research criteria.

Today’s standard of care dictates that ADT treatment should not be considered successful in obtaining castrate levels until the testosterone levels are under 20 ng/dl, not 50 ng/dl.

At Cancer ABCs we have significant concerns and disagree with the study author’s conclusions describing the adverse effects as being mild, short-lived and only including just 8.9% of the subjects.   The researchers used the measure of castration of 50 ng/dl; we believe that the proper standard should be 20 ng/dl.

Without seeing the raw data, we cannot say if this more stringent measure was used how many additional men would have been determined to have become non-castrate, but we do assume that the number would be much more significant.

Given the data, we believe that there should be a clinical recommendation that Casodex is given before the transition just like we give when initially starting Lupron.  Providing Casodex as a part of the drug transition will protect the 8.9% of the known men who will experience a flare as well as those unknown additional numbers whose testosterone levels might fall between 20 ng/dl and 50 ng/dl.


Zuckerman JM, Eure G, Malcolm J, Currie L, Given R Urology. 2014 Mar;83(3):670-4.

doi: 10.1016/j.urology.2013.10.036

PMID: 24360065

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 Appendiceal Cancer a rare cancer.