BACKGROUND Biosynthesis of extragonadal androgen may contribute to the progression of castration-resistant prostate cancer. We evaluated whether abiraterone acetate, an inhibitor of androgen biosynthesis, prolongs overall survival among patients with metastatic castration-resistant prostate cancer who have received chemotherapy. METHODS We randomly assigned, in a 2:1 ratio, 1195 patients who had previously received docetaxel to receive 5 mg of prednisone twice daily with either 1000 mg of abiraterone acetate (797 patients) or placebo (398 patients). The primary end point was overall survival. The secondary end points included time to prostate-specific antigen (PSA) progression (elevation in the PSA level according to prespecified criteria), progression-free survival according to radiologic findings based on prespecified criteria, and the PSA response rate. RESULTS After a median follow-up of 12.8 months, overall survival was longer in the abiraterone acetate–prednisone group than in the placebo–prednisone group (14.8 months vs. 10.9 months; hazard ratio, 0.65; 95% confidence interval, 0.54 to 0.77; P<0.001). Data were unblinded at the interim analysis, since these results exceeded the preplanned criteria for study termination. All secondary end points, including time to PSA progression (10.2 vs. 6.6 months; P<0.001), progression-free survival (5.6 months vs. 3.6 months; P<0.001), and PSA response rate (29% vs. 6%, P<0.001), favored the treatment group. Mineralocorticoid-related adverse events, including fluid retention, hypertension, and hypokalemia, were more frequently reported in the abiraterone acetate–prednisone group than in the placebo–prednisone group. CONCLUSIONS The inhibition of androgen biosynthesis by abiraterone acetate prolonged overall survival among patients with metastatic castration-resistant prostate cancer who previously received chemotherapy. (Funded by Cougar Biotechnology; COU-AA-301 ClinicalTrials.gov number, NCT00638690.)

/pdf/abiraterone-and-increased-survival-in-metastatic-prostate-2zpqt2rwwy.pdf

Abiraterone and Increased Survival in Metastatic Prostate Cancer

Background Enzalutamide (formerly called MDV3100) targets multiple steps in the androgen-receptor–signaling pathway, the major driver of prostate-cancer growth. We aimed to evaluate whether enzalutamide prolongs survival in men with castration-resistant prostate cancer after chemotherapy. Methods In our phase 3, double-blind, placebo-controlled trial, we stratified 1199 men with castration-resistant prostate cancer after chemotherapy according to the Eastern Cooperative Oncology Group performance-status score and pain intensity. We randomly assigned them, in a 2:1 ratio, to receive oral enzalutamide at a dose of 160 mg per day (800 patients) or placebo (399 patients). The primary end point was overall survival. Results The study was stopped after a planned interim analysis at the time of 520 deaths. The median overall survival was 18.4 months (95% confidence interval [CI], 17.3 to not yet reached) in the enzalutamide group versus 13.6 months (95% CI, 11.3 to 15.8) in the placebo group (hazard ratio for de...

/pdf/increased-survival-with-enzalutamide-in-prostate-cancer-1v77512mc7.pdf

Increased Survival with Enzalutamide in Prostate Cancer after Chemotherapy

A b s t r ac t Background Abiraterone acetate, an androgen biosynthesis inhibitor, improves overall survival in patients with metastatic castration-resistant prostate cancer after chemotherapy. We evaluated this agent in patients who had not received previous chemotherapy. Methods In this double-blind study, we randomly assigned 1088 patients to receive abiraterone acetate (1000 mg) plus prednisone (5 mg twice daily) or placebo plus prednisone. The coprimary end points were radiographic progression-free survival and overall survival. Results The study was unblinded after a planned interim analysis that was performed after 43% of the expected deaths had occurred. The median radiographic progressionfree survival was 16.5 months with abiraterone–prednisone and 8.3 months with prednisone alone (hazard ratio for abiraterone–prednisone vs. prednisone alone, 0.53; 95% confidence interval [CI], 0.45 to 0.62; P<0.001). Over a median follow-up period of 22.2 months, overall survival was improved with abiraterone–prednisone (median not reached, vs. 27.2 months for prednisone alone; hazard ratio, 0.75; 95% CI, 0.61 to 0.93; P = 0.01) but did not cross the efficacy boundary. Abiraterone–predni sone showed superiority over prednisone alone with respect to time to initiation of cytotoxic chemotherapy, opiate use for cancer-related pain, prostate-specific antigen progression, and decline in performance status. Grade 3 or 4 mineralocorticoid-related adverse events and abnormalities on liver-function testing were more common with abiraterone–prednisone. Conclusions Abiraterone improved radiographic progression-free survival, showed a trend toward improved overall survival, and significantly delayed clinical decline and initiation of chemotherapy in patients with metastatic castration-resistant prostate cancer. (Funded by Janssen Research and Development, formerly Cougar Biotechnology; ClinicalTrials.gov number, NCT00887198.)

/pdf/abiraterone-in-metastatic-prostate-cancer-without-previous-502otrb7df.pdf

Abiraterone in Metastatic Prostate Cancer without Previous Chemotherapy

Purpose To update eligibility and outcome measures in trials that evaluate systemic treatment for patients with progressive prostate cancer and castrate levels of testosterone. Methods A committee of investigators experienced in conducting trials for prostate cancer defined new consensus criteria by reviewing previous criteria, Response Evaluation Criteria in Solid Tumors (RECIST), and emerging trial data.

/pdf/design-and-end-points-of-clinical-trials-for-patients-with-4ixilt7epd.pdf

Design and end points of clinical trials for patients with progressive prostate cancer and castrate levels of testosterone: recommendations of the Prostate Cancer Clinical Trials Working Group.

n this prospective, multicenter, phase 3 trial, 1088 patients with asymptomatic or mildly symptomatic Imetastatic castrate-resistant prostate cancer (mCRPC) were randomized to receive abiraterone (1000 mg) plus prednisone (5 mg twice daily) or placebo plus prednisone. Abiraterone inhibits CYP-17, a crucial enzyme in androgen biosynthesis in the testes, adrenal glands, and in prostate cancer cells. The trial was designed with 2 coprimary end points: radiographic progression-free survival and overall survival. This report was based on a planned interim analysis after 43% (333 of 773) of expected deaths had occurred. The findings were significant enough to warrant unblinding so that patients in the placebo arm could be offered abiraterone. The progression-free survival improved from 8.3 months to 16.5 months with abiraterone (hazard ratio, 0.53; 95% confidence interval, 0.45-0.62; P <.001). The median overall survival was not reached in the abiraterone group but was 27.2 months in the control arm (hazard ratio, 0.75; 95% confidence interval, 0.61-0.93; P 1⁄4 .0097). This did not reach the prespecified P value of .0008 to achieve statistical significance, so that at the time of this interim analysis, it can only be concluded that abiraterone showed a strong trend toward improved survival. Further benefits were observed in secondary end points, including time to initiation of cytotoxic chemotherapy (25.2 vs 16.8 months), to opiate use for cancer-related pain (not reached vs 23.7 months), to prostate-specific antigen progression (11.1 vs 5.6 months), and to a 1-point decline in Eastern Cooperative Oncology Group performance status (12.3 vs 10.9 months). These important milestones in the course of mCRPC were all delayed. Toxicity related to abiraterone was observed, but because prednisone was administered in both treatment groups, rates of toxicity in the control arm were not much different. Grade 3 or 4 adverse events were reported by 48% of patients in the abiraterone arm and by 42% of patients in the control arm. Fatigue, arthralgia, and peripheral edema were important adverse effects observed more frequently in the abiraterone arm. Other signs of

Commentary on: Abiraterone in Metastatic Prostate Cancer Without Previous Chemotherapy

The androgen-signaling pathway is critical to the development and progression of prostate cancer and androgen ablation is a mainstay of therapy for this disease. We performed a genome-wide expression analysis of human prostate cancer during androgen ablation therapy to identify genes regulated by androgen and genes differentially expressed after the development of resistance. Six hundred and fifty-four of 63,175 probe sets detected significant expression changes after 3 months of treatment with goserelin and flutamide. This included 149 genes that were also differentially expressed 36 hours after androgen withdrawal in LNCaP cells. These genes reflect the physiological changes that occur in treated tumors and include potential direct targets of the androgen receptor. Expression profiles of androgen ablation-resistant tumors demonstrated that many of the gene expression changes detected during therapy were no longer present suggesting a reactivation of the androgen response pathway in the absence of exogenous hormone. Therapy resistance was associated with differential expression of a unique set of genes that reflect potential mechanisms of reactivation. Specifically an up-regulation of the androgen receptor and key enzymes for steroid biosynthesis suggest that resistant tumors have increased sensitivity to and endogenous synthesis of androgenic hormones. The specific pathways of reactivation provide opportunities for classification of resistant tumors and targeted therapies.

/pdf/gene-expression-analysis-of-human-prostate-carcinoma-during-43xkq7z9b0.pdf

Jeff Holzbeierlein

Papers

Gene Expression Analysis of Human Prostate Carcinoma during Hormonal Therapy Identifies Androgen-Responsive Genes and Mechanisms of Therapy Resistance