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Clinical outcomes and survival surrogacy studies of prostate-specific antigen declines following enzalutamide in men with metastatic castration-resistant prostate cancer previously treated with docetaxel.

ABSTRACT: In the AFFIRM trial, enzalutamide significantly increased overall survival (OS) for men with metastatic castration-resistant prostate cancer (mCRPC) after chemotherapy versus placebo and significantly decreased prostate-specific antigen (PSA) levels. The goal of this post hoc analysis was to associate levels of PSA decline from baseline after enzalutamide with clinical outcomes in the postchemotherapy mCRPC setting.Men in the AFFIRM trial (n = 1199) were grouped by maximal PSA decline in the first 90 days of treatment. Kaplan-Meier estimates evaluated the association of defined PSA changes from baseline with OS, progression-free survival (PFS), radiographic PFS (rPFS), and pain response. Each PSA decline category was assessed for OS surrogacy using Prentice criteria, proportion of treatment effect explained (PTE), and proportion of variation explained.Men treated with enzalutamide had improved OS (hazard ratio, 0.63; P < .001) and higher rates of PSA decline (odds ratio, >19.0; P < .001) versus placebo. PSA declines of any, ?30%, ?50%, and ?90% with enzalutamide were strongly associated with greater OS, PSA PFS, rPFS (P < .001), and pain response (P < .026) versus PSA increase/no decline. Any, ?30%, and ?50% declines in PSA resulted in the PTE range of 1.07-1.29, where treatment was no longer significant after adjustment for decline measures (P > .20).PSA declines of any, ?30%, and ?50% following enzalutamide were associated with greater clinical and pain response and improvements in PFS and OS. Surrogacy of PSA decline for OS was not fully established, possibly due to lack of PSA declines with placebo, and discordant results between PSA and imaging responses over time, and because some declines were not durable due to rapid resistance development. However, a lack of PSA decline by 90 days following enzalutamide treatment was a poor prognosis indicator in this setting. Conclusions from sensitivity analyses of maximal PSA decline from baseline over the entire treatment period are consistent with PSA declines restricted to the first 90 days. Cancer 2017;123:2303-2311. © 2017 American Cancer Society.

SUBMITTER: Armstrong AJ

PROVIDER: S-EPMC5484320 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Clinical outcomes and survival surrogacy studies of prostate-specific antigen declines following enzalutamide in men with metastatic castration-resistant prostate cancer previously treated with docetaxel.

Armstrong Andrew J AJ Saad Fred F Phung De Dmuchowski Carl C Shore Neal D ND Fizazi Karim K Hirmand Mohammad M Forer David D Scher Howard I HI Bono Johann De J

Cancer 20170207 12

<h4>Background</h4>In the AFFIRM trial, enzalutamide significantly increased overall survival (OS) for men with metastatic castration-resistant prostate cancer (mCRPC) after chemotherapy versus placebo and significantly decreased prostate-specific antigen (PSA) levels. The goal of this post hoc analysis was to associate levels of PSA decline from baseline after enzalutamide with clinical outcomes in the postchemotherapy mCRPC setting.<h4>Methods</h4>Men in the AFFIRM trial (n = 1199) were groupe ...[more]

PMID: 28171710

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Project description:Two randomized clinical trials have demonstrated a survival advantage with enzalutamide over placebo in both docetaxel (D)-pretreated and D-naïve metastatic castration-resistant prostate cancer (mCRPC) patients. Cross-resistance between androgen receptor-directed therapies and taxanes has been suggested, possibly leading to lower efficacy of enzalutamide in the post-D setting.We aimed to examine the impact of prior D treatment on the clinical activity of enzalutamide in patients with mCRPC. We retrospectively reviewed an institutional database to identify men with mCRPC treated with standard-of-care enzalutamide. Patients were classified as D-naïve or D-pretreated. The efficacy end points were prostate-specific antigen (PSA) response rates (??50% PSA decline), time to PSA progression (TTPP) and clinical/radiographic progression-free survival (PFS) in response to enzalutamide. Differences between groups (D-naïve and D-pretreated) were assessed by univariate and multivariable analyses using logistic and Cox regression models.One-hundred-seven (107) consecutive patients were included: 60 were D-pretreated and 47 were D-naïve. PSA responses were 43.2% in D-naïve patients and 25.4% in D-pretreated patients (P?=?0.089). Median TTPP was 7.2 months (95% CI?=?4.5?-?17.2) in the D-naïve group versus 2.6 mo (95% CI?=?1.9?-?3.5) in the D-pretreated group (P?<?0.0001). Median PFS was not reached for D-naïve men and was 3.3 mo (95% CI?=?2.5?-?4.8) for D-pretreated men (P?<?0.0001). After adjusting for potential confounders including prior abiraterone use, differences remained statistically significant for TTPP (HR?=?2.32; 95% CI?=?1.19?-?4.50; P?=?0.013) and marginally significant for PFS (HR?=?1.90; 95% CI?=?0.94?-?3.84; P?=?0.073) in multivariable analyses. Among patients who achieved a PSA response to enzalutamide (n?=?34), results suggested a trend towards shorter duration of response in D-pretreated patients.The clinical activity of enzalutamide appears to be blunted in patients who have previously received docetaxel chemotherapy. These results support the concept of cross-resistance between these two agents.

Project description:BackgroundThe optimal sequencing of the multiple active agents now available for metastatic castration-resistant prostate cancer (mCRPC) is unclear. Prior reports have suggested diminished responses to sequential lines of androgen receptor (AR)-targeted therapies, but it is unknown whether subsequent taxane-based chemotherapy may be more effective than sequential AR-targeting treatment. We sought to evaluate the clinical activity of enzalutamide versus docetaxel in men with mCRPC who progressed on abiraterone.MethodsWe performed a single-institution retrospective analysis of consecutive mCRPC patients who had progressed on abiraterone therapy and subsequently received either enzalutamide (n=30) or docetaxel (n=31). We evaluated clinical outcomes including prostate-specific antigen decline of >30% (PSA30) or >50% (PSA50), PSA-progression-free survival (PSA-PFS), and clinical/radiographic PFS. We performed multivariable modeling to control for baseline and on-treatment differences between groups.ResultsCompared to subjects who received enzalutamide post-abiraterone, subjects who received docetaxel post-abiraterone had more bone metastases, more visceral metastases, higher baseline PSA, and had more frequent PSA tests while on-treatment. There were no significant differences in PSA30 (41% for enzalutamide vs. 53% for docetaxel) or PSA50 (34% vs. 40%) response rates between the two groups; there remained no difference after stratifying by presence/absence of prior response to abiraterone. Median PSA-PFS was 4.1 versus 4.1 months for the enzalutamide and docetaxel cohorts, respectively (HR 1.35, 95% CI, 0.53-3.66, P=0.502). Median PFS was 4.7 versus 4.4 months, respectively (HR 1.44, 95% CI, 0.77-2.71, P=0.257). PSA-PFS and PFS did not differ after stratifying by prior response to abiraterone. In multivariable analyses, there were no significant differences in PSA-PFS or PFS between the two groups.ConclusionsTreatment with either enzalutamide or docetaxel produced modest PSA responses and PFS intervals in this abiraterone-pretreated mCRPC population. In this retrospective study with small sample size, no significant differences in outcomes were observed between groups. Therefore, either enzalutamide or docetaxel may be a reasonable option in men who have progressed on abiraterone.

Project description:BackgroundMen with nonmetastatic, castration-resistant prostate cancer and a rapidly rising prostate-specific antigen (PSA) level are at high risk for metastasis. We hypothesized that enzalutamide, which prolongs overall survival among patients with metastatic, castration-resistant prostate cancer, would delay metastasis in men with nonmetastatic, castration-resistant prostate cancer and a rapidly rising PSA level.MethodsIn this double-blind, phase 3 trial, we randomly assigned, in a 2:1 ratio, men with nonmetastatic, castration-resistant prostate cancer and a PSA doubling time of 10 months or less who were continuing androgen-deprivation therapy to receive enzalutamide (at a dose of 160 mg) or placebo once daily. The primary end point was metastasis-free survival (defined as the time from randomization to radiographic progression or as the time to death without radiographic progression).ResultsA total of 1401 patients (median PSA doubling time, 3.7 months) underwent randomization. As of June 28, 2017, a total of 219 of 933 patients (23%) in the enzalutamide group had metastasis or had died, as compared with 228 of 468 (49%) in the placebo group. The median metastasis-free survival was 36.6 months in the enzalutamide group versus 14.7 months in the placebo group (hazard ratio for metastasis or death, 0.29; 95% confidence interval, 0.24 to 0.35; P<0.001). The time to the first use of a subsequent antineoplastic therapy was longer with enzalutamide treatment than with placebo (39.6 vs. 17.7 months; hazard ratio, 0.21; P<0.001; such therapy was used in 15% vs. 48% of patients) as was the time to PSA progression (37.2 vs. 3.9 months; hazard ratio, 0.07; P<0.001; progression occurred in 22% vs. 69% of patients). At the first interim analysis of overall survival, 103 patients (11%) receiving enzalutamide and 62 (13%) receiving placebo had died. Adverse events of grade 3 or higher occurred in 31% of the patients receiving enzalutamide, as compared with 23% of those receiving placebo.ConclusionsAmong men with nonmetastatic, castration-resistant prostate cancer with a rapidly rising PSA level, enzalutamide treatment led to a clinically meaningful and significant 71% lower risk of metastasis or death than placebo. Adverse events were consistent with the established safety profile of enzalutamide. (Funded by Pfizer and Astellas Pharma; PROSPER ClinicalTrials.gov number, NCT02003924 .).

Dataset Information

Clinical outcomes and survival surrogacy studies of prostate-specific antigen declines following enzalutamide in men with metastatic castration-resistant prostate cancer previously treated with docetaxel.

Publications

Clinical outcomes and survival surrogacy studies of prostate-specific antigen declines following enzalutamide in men with metastatic castration-resistant prostate cancer previously treated with docetaxel.

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