Clinical outcomes of abiraterone acetate (AA) or enzalutamide (E) as first-line therapy (Rx) for men aged ≥75 with metastatic castration-resistant prostate cancer (mCRPC) according to previous use of docetaxel (D) for metastatic castration-sensitive prostate cancer (mCSPC) in a multicenter international registry: A SPARTACUSS – Meet-URO 26 study

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Background: The optimal management of mCRPC in men aged ≥75 is challenging, and there is a paucity of clinical data in the literature. Although AA and E are commonly used as 1st line Rx for mCRPC, it is unclear whether use of upfront D for mCSPC may impact their clinical efficacy or safety in this elderly population. Methods: Patients aged ≥75 who started AA or E as 1st line Rx for mCRPC within January 2015 - April 2019 were identified from the IRB approved databases of 10 institutions in Europe, South and North America. Demographic and clinicopathological data were collected from available medical records, including Gleason, prior local therapy, newly diagnosed metastatic disease, disease volume, ECOG, PSA and sites of metastases. Patients were classified by use of upfront D for mCSPC. The primary endpoints were overall survival (OS) from AA/E onset and OS from ADT start and safety of AA/E. The endpoints distributions including median (95% CI) were estimated by Kaplan-Meier method. Results: Of the 337 patients selected, 24 (7.1%) received ADT+D and 313 (92.9%) ADT alone for mCSPC. Patients with ADT+D tended to be younger (78 vs 81, p=0.022) and, albeit not statistically significant, had higher rates of Gleason score >8 (81.0% vs 62.6%, p=0.10), newly diagnosed (83.3% vs 65.6%, p=0.08) and high volume disease (45.8% vs 34.6%, p=0.28), compared to those with ADT alone. Median follow-up was 18.8 months. No significant difference of OS from ADT start or from AA/E onset was observed between the 2 cohorts (see table). Despite OS from ADT start being longer in those having ADT+D, OS from AA/E start was approximately 2 years in both cohorts. Rates of adverse events (AEs) of any grade (58.3% vs 52.1%, p=0.67) and grade ≥3 (12.5% vs 15.7%, p=1.0) did not significantly differ between the 2 cohorts. Conclusions: While limited by small sample size for ADT+D and retrospective study design, patients aged ≥75 having AA/E as 1st line mCRPC Rx showed similar survival outcomes and tolerability regardless of previous use of D for mCSPC. [Table: see text]

Efficacy and safety of docetaxel (D) vs androgen-receptor signaling inhibitors (ARSi) as second-line therapy (Rx) after progression on alternative ARSi as first-line Rx for patients who are elderly (≥75 years old) with metastatic castration-resistant prostate cancer (mCRPC) in a multicenter international database: A SPARTACUSS–Meet-URO 26 study

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Background: About 2/3 of all prostate cancer (PCa) deaths occur in patients aged ≥75, who are frequently diagnosed with advanced PCa. ARSi abiraterone acetate (AA) and enzalutamide (E) are the most common 1st line Rx for patients with mCRPC. Yet, the optimal treatment sequence for the elderly ≥75 after ARSi failure is still unclear. Methods: Using available medical records, patients aged ≥75 who started ARSi as 1st line Rx for mCRPC within January 2015 - April 2019 and, upon progression, 2nd line alternative ARSi or D were identified from the IRB approved hospital registries of 10 centers in Europe, North and South America. Patients were categorized by type of 2nd line Rx for mCRPC into cohorts AA/E and D. Primary endpoints were overall survival (OS) from 1st line AA/E start, OS and radiographic progression-free survival (rPFS) from 2nd line Rx start, and safety. The Kaplan Meier method was used to calculate endpoint distributions and medians (95% CI). Results: Of the 122 patients identified, 57 (46.7%) had AA/E and 65 (53.3%) D, as 2nd line Rx for mCRPC. Median follow-up was 26.3 months (95% CI, 23.1-27.9 months). Cohort AA/E tended to be older (81 vs 78 years; p=0.001) and with high-volume disease (45.5% vs 25.0%; p=0.022) compared to cohort D. No significant difference in OS from 1st line ARSi onset and OS or rPFS from 2nd line Rx start was found between the 2 cohorts. Cohort AA/E had longer rPFS than cohort D, albeit not significant (18.5 vs 12.0 months; p=0.13). Rates of adverse events (AEs) of any grade (42.1 vs 53.8; p=0.21) and AEs of grade ≥3 (19.3% vs 18.5%; p=1.0) did not show significant differences between the 2 cohorts. Conclusions: Within the limitations of small cohorts and retrospective design, treatment sequences with 2nd line AA/E or D after failure of 1st line alternative ARSi for mCRPC showed similar efficacy and safety in the elderly ≥75 years old.

Correlation between time to prostate cancer metastasis and overall survival after androgen-deprivation therapy initiation

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Background: Currently,overall survival (OS) is used to determine treatment efficacy in trials for advanced prostate cancer (PC). Reliable intermediate endpoints could hasten drug development efforts. We therefore sought to determine the association between an intermediate endpoint—time to metastasis (TTM)—and OS in PC patients receiving androgen deprivation therapy (ADT) for biochemical recurrence (BCR). Methods: The Dana-Farber PC database identified 415 patients who received ADT for non-metastatic BCR with median 6.4 years follow-up. Associations between TTM and OS were measured from (i) time of ADT initiation (n=398) and (ii) time of castration-resistance (n=247) using a non-parametric Kendall tau rank correlation for bivariate time to event outcomes. A Cox regression model was used to assess the association of development of metastasis and OS for landmark timepoints. Results: Among 398 subjects analyzed from start of ADT, 180 (45%) developed metastases with median TTM 6.25 years. A total of 152 (38%) died, with a median OS of 8.5 years. For men developing metastases within five years of ADT initiation, hazard ratio (HR) for mortality was 7.42 (p<0.0001, 95% CI 4.18-13.17). Among 247 subjects assessed from time of castration resistant PC (CRPC), 172 (70%) developed metastases with a median TTM 2.6 years. In this subgroup, 140 (56%) patients died with median OS 5.25 years. For men developing metastases within three years of developing castration-resistance, HR for mortality was 5.25 (p<0.0001, 95% CI 3.20-8.61). Overall, correlation between TTM and OS from ADT initiation and OS was 0.25 (P<0.0001, 95% CI 0.20-0.29). Correlation between TTM and OS from CRPC was 0.32 (P<0.0001, 95% CI 0.25-0.37). Conclusions: TTM was significantly correlated with OS in PC patients treated with ADT for BCR. Prospective data in a large validation cohort will help determine whether TTM is suitably predictive of OS to serve as a primary endpoint in clinical trials.