Multicenter prospective study of switching from GnRH agonists to GnRH antagonist for patients with early stage of castration resistant prostate cancer as a second-line hormonal therapy.

183Background: It was reported that GnRH antagonist could extend progression free survival for prostate cancer patients significantly longer than GnRH agonist in a first line hormonal therapy. However, the usefulness of switching from GnRH agonist to GnRH antagonist as a second hormonal therapy remains obscure. We performed a multicentral prospective study to investigate whether the switching from GnRH agonist to GnRH antagonist (degalerix) for patients with castration resistant prostate cancer (CRPC) as the 2nd line hormonal therapy was effective. Methods: 37 patients who were pathologically diagnosed as prostatic adenocarcinoma and developed CRPC after 1st line hormonal therapy with GnRH agonist plus anti-androgens were enrolled. After confirming anti-androgen withdrawal syndrome, they were treated with switching from GnRH agonists to degalerix. The primary endpoint was PSA response (PSA decline or up to 10% over baseline PSA). Secondary endpoints were the time to 25% PSA increase from the baseline (PSA...