Efficacy and Safety of Radiotherapy Plus Relugolix in Men With Localized or Advanced Prostate Cancer

Importance

Combination androgen deprivation therapy (ADT) with radiotherapy is commonly used for patients with localized and advanced prostate cancer.

Objective

To assess the efficacy and safety of the oral gonadotropin-releasing hormone antagonist relugolix with radiotherapy for treating prostate cancer.

Design, Setting, and Participants

This multicenter post hoc analysis of patients with localized and advanced prostate cancer receiving radiotherapy in 2 randomized clinical trials (a phase 2 trial of relugolix vs degarelix, and a subset of the phase 3 HERO trial of relugolix vs leuprolide acetate) included men who were receiving radiotherapy and short-term (24 weeks) ADT (n = 103) from 2014 to 2015 and men receiving radiotherapy and longer-term (48 weeks) ADT (n = 157) from 2017 to 2019. The data were analyzed in November 2022.

Interventions

Patients receiving short-term ADT received relugolix, 120 mg, orally once daily (320-mg loading dose) or degarelix, 80 mg, 4-week depot (240-mg loading dose) for 24 weeks with 12 weeks of follow-up. Patients receiving longer-term ADT received relugolix, 120 mg, orally once daily (360-mg loading dose) or leuprolide acetate injections every 12 weeks for 48 weeks, with up to 90 days of follow-up.

Main Outcomes and Measures

Castration rate (testosterone level <50 ng/dL [to convert to nmol/L, multiply by 0.0347) at all scheduled visits between weeks 5 and 25 for patients receiving short-term ADT and weeks 5 and 49 for patients receiving longer-term ADT.

Results

Of 260 patients (38 Asian [14.6%], 23 Black or African American [8.8%], 21 Hispanic [8.1%], and 188 White [72.3%] individuals), 164 (63.1%) received relugolix. Relugolix achieved castration rates of 95% (95% CI, 87.1%-99.0%) and 97% (95% CI, 90.6%-99.0%) among patients receiving short-term and longer-term ADT, respectively. Twelve weeks post-short-term relugolix, 34 (52%) achieved testosterone levels to baseline or more than 280 ng/dL. Ninety days post longer-term ADT, mean (SD) testosterone levels were 310.5 (122.4) (106.7) ng/dL (relugolix; n = 15) vs 53.0 ng/dL (leuprolide acetate; n = 8) among the subset assessed for testosterone recovery. Castration resistance-free survival was not statistically different between the relugolix and leuprolide acetate cohorts (hazard ratio, 0.97; 95% CI, 0.35-2.72; P = .62). Adverse events grade 3 or greater for short-term or longer-term relugolix (headache, hypertension, and atrial fibrillation) were uncommon (less than 5%).

Conclusions and Relevance

The results of these 2 randomized clinical trials suggest that relugolix rapidly achieves sustained castration in patients with localized and advanced prostate cancer receiving radiotherapy. No new safety concerns were identified when relugolix was used with radiotherapy.

A Phase 2 Randomized Open-label Study of Oral Darolutamide Monotherapy Versus Androgen Deprivation Therapy in Men with Hormone-sensitive Prostate Cancer (EORTC-GUCG 1532)

BACKGROUND AND OBJECTIVE

Darolutamide is an androgen receptor inhibitor that increases overall survival in combination with androgen deprivation therapy (ADT) in patients with metastatic hormone-sensitive and nonmetastatic castration-resistant prostate cancer (PCa). This phase 2 study assessed the efficacy and safety of darolutamide as monotherapy without ADT in patients with eugonadal testosterone levels.

METHODS

This was a 24-wk, open-label, randomized study of patients with hormone-sensitive, histologically confirmed PCa requiring gonadotropin-releasing hormone (GnRH); an Eastern Cooperative Oncology Group performance status score of 0/1; and life expectancy >1 yr. All patients received darolutamide 600 mg bid or a commercially available GnRH analog. The primary endpoint is a prostate-specific antigen (PSA) response, defined as a ≥80% decline at week 24 relative to baseline in the darolutamide study arm. The GnRH arm is used as an internal control. The secondary endpoints included changes in T levels, safety/tolerability, and quality of life.

KEY FINDINGS AND LIMITATIONS

Among 61 men enrolled, the median (range) age was 72 yr (53-86 yr); 42.6% of them had metastases. In the darolutamide arm, the evaluable population with available PSA values at baseline and week 24 consisted of 23 patients. Twenty-three (100%) evaluable darolutamide patients achieved a PSA decline of >80% at week 24 (primary endpoint), with a median (range) decrease of -99.1% (-91.9%, -100%). Serum T levels increased by a median (range) of 44.3 (5.7-144.0) at week 24, compared with baseline. In the darolutamide arm, 48.4% of men reported drug-related adverse events (AEs; mostly grade 1 or 2). The most frequent treatment-emergent AEs included gynecomastia (35.5%), fatigue (12.9%), hot flush (12.9%), and hypertension (12.9%). Health-related quality of life measures are descriptive, and GnRH arm results will be presented as an internal reference.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Darolutamide monotherapy was associated with a significant PSA response in nearly all men with hormone-naïve PCa. Testosterone-level changes and most common AEs (gynecomastia, fatigue, hypertension, and hot flush) were consistent with potent androgen receptor inhibition.

PATIENT SUMMARY

In this study, we report the first use of darolutamide, a novel antiandrogen, as monotherapy without androgen deprivation therapy (ADT). The study shows that darolutamide induce a profound suppression of prostate-specific antigen in all patients, with a safety profile different from that of ADT.

Discrete-Choice Experiment to Understand the Preferences of Patients with Hormone-Sensitive Prostate Cancer in the USA, Canada, and the UK

BACKGROUND

Treatment options for patients with metastatic hormone-sensitive prostate cancer (mHSPC) have broadened, and treatment decisions can have a long-lasting impact on patients' quality of life. Data on patient preferences can improve therapeutic decision-making by helping physicians suggest treatments that align with patients' values and needs.

OBJECTIVE

This study aims to quantify patient preferences for attributes of chemohormonal therapies among patients with mHSPC in the USA, Canada, and the UK.

METHODS

A discrete-choice experiment survey instrument was developed and administered to patients with high- and very-high-risk localized prostate cancer and mHSPC. Patients chose between baseline androgen-deprivation therapy (ADT) alone and experimentally designed, hypothetical treatment alternatives representing chemohormonal therapies. Choices were analyzed using logit models to derive the relative importance of attributes for each country and to evaluate differences and similarities among patients across countries.

RESULTS

A total of 550 respondents completed the survey (USA, 200; Canada, 200; UK, 150); the mean age of respondents was 64.3 years. Treatment choices revealed that patients were most concerned with treatment efficacy. However, treatment-related convenience factors, such as route of drug administration and frequency of monitoring visits, were as important as some treatment-related side effects, such as skin rash, nausea, and fatigue. Patient preferences across countries were similar, although patients in Canada appeared to be more affected by concomitant steroid use.

CONCLUSION

Patients with mHSPC believe the use of ADT alone is insufficient when more effective treatments are available. Efficacy is the most significant driver of patient choices. Treatment-related convenience factors can be as important as safety concerns for patients.

A phase 2 randomized open-label study of oral darolutamide monotherapy vs. androgen deprivation therapy in men with hormone-naive prostate cancer (EORTC-GUCG 1532)

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Background: Darolutamide is androgen-receptor (AR) inhibitor with low blood–brain barrier penetration and limited potential for clinically relevant drug–drug interactions. Darolutamide has been shown to increase overall survival in combination with androgen deprivation therapy (ADT) in patients with newly diagnosed metastatic hormone sensitive prostate cancer (PC) and, in combination with docetaxel, in men with non-metastatic castration resistant PC. This phase 2 study assessed the efficacy and safety of DARO as a monotherapy without ADT in patients with non-castrate testosterone (T) levels (≥230 ng/dL). Methods: This was a 24-wk, open-label, randomized study of patients with hormone-naïve, histologically confirmed prostate cancer (all stages, with a max of 4 metastatic lesions) requiring hormonal treatment, an ECOG PS score of 0, and a life expectancy >1 y. All patients received DARO 600 mg bid or commercially available LHRH analogue. The primary endpoint is PSA response defined as a ≥ 80% decline at week 24 relative to baseline, in the DARO study arm. The ADT arm is used as an internal control. Secondary endpoints included changes in T levels, safety/tolerability, and quality of life. Results: Among 61 men enrolled, the median (range) age was 72 y (53-86y); 49.2% had metastases; 14.8% and 62.3% had undergone prostatectomy or radiotherapy before study entry. The median (range) of PSA at baseline was 8.9 ng/mL (2.2-333.8). In the DARO arm, the evaluable population with available PSA values at baseline and week 24 consisted of 21 patients. The PSA response rate (>80% PSA decline at wk 24) was 100%, with a median (range) decrease of -99.6% (-94.3, -100) at wk 24 in the DARO arm. Serum T levels increased by a median (range) of 43.4% (5.7-144.0) at wk 24, compared with baseline. In the DARO arm, 45.2% of men reported drug-related AEs (mostly Grade 1 or 2). Most frequent treatment-emergent AEs included gynaecomastia (19.4%), fatigue (12.9%), and hot flush (12.9%). 3.1% of men experienced SAEs, none of which were drug related. HR-QoL measures and ADT arm results will be presented as internal reference. Conclusions: DARO monotherapy (600 mg bid) was associated with significant PSA response in nearly all men with hormone-naïve prostate cancer. Testosterone level changes and most common AEs (gynecomastica, fatigue and hot flush) were consistent with potent AR inhibition. Clinical trial information: NCT02972060 .

Efficacy and safety of darolutamide (DARO) in combination with androgen-deprivation therapy (ADT) and docetaxel (DOC) by disease volume and disease risk in the phase 3 ARASENS study

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Background: In ARASENS (NCT02799602), DARO plus ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI: 0.57–0.80; P<0.0001) vs placebo (PBO) + ADT + DOC in patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC), with similar overall incidences of treatment-emergent adverse events (TEAEs) between groups. The effect of DARO on overall survival (OS) was consistent across prespecified subgroups, including de novo and recurrent disease. For pts with mHSPC, outcomes based on disease volume and risk provide additional information to clinicians. Methods: Pts with mHSPC were randomized 1:1 to DARO 600 mg twice daily or PBO, with ADT + DOC. High-volume disease was defined as visceral metastases and/or ≥4 bone metastases with ≥1 beyond the vertebral column/pelvis (CHAARTED criteria). High-risk disease was defined as ≥2 risk factors: Gleason score ≥8, ≥3 bone lesions, and presence of measurable visceral metastasis (LATITUDE criteria). OS for these subgroups was assessed using an unstratified Cox regression model. Results: Of 1305 pts in the full analysis set, 1005 (77%) had high-volume disease, 912 (70%) had high-risk disease, 300 (23%) had low-volume disease, and 393 (30%) had low-risk disease. DARO + ADT + DOC prolonged OS regardless of high- or low-volume disease with HRs of 0.69 and 0.68 vs PBO + DOC + ADT, respectively. OS benefit of DARO vs PBO was also similar for pts with high- or low-risk disease. DARO improved clinically relevant secondary endpoints vs PBO in high/low-volume and risk subgroups, with HRs generally in the range of those observed in the overall population. Incidences of TEAEs were consistent with the overall ARASENS population across subgroups by high/low volume and high/low risk. Conclusions: In pts with mHSPC, the benefits of early treatment intensification with DARO + ADT + DOC on OS and key pt-relevant secondary efficacy endpoints vs PBO + ADT + DOC were similar in patients with high- and low-volume as well as high- and low-risk mH+SPC. The favorable safety profile of DARO was reconfirmed in high/low-volume and high/low-risk populations. DARO + ADT + DOC sets a new standard of care for pts with mHSPC. Clinical trial information: NCT02799602 . [Table: see text]

Efficacy and safety of abiraterone acetate plus prednisone and androgen deprivation therapy +/- docetaxel in older patients (≥70 years), with de novo metastatic-castration sensitive prostate cancer, compared to younger patients (<70 years): The PEACE-1 trial

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Background: Metastatic castration-sensitive prostate cancer (mCSPC) primarily affects older men (OM). In this post-hoc analysis we investigated the safety and efficacy of abiraterone acetate + prednisone (AAP) in older (≥ 70 years) and younger (< 70 years) patients in PEACE-1. Methods: Men with de novo mCSPC were allocated to standard of care (SOC), SOC + AAP, SOC + radiotherapy (RXT), or SOC + AAP + RXT in this 2x2 design phase 3 trial. SOC was initially androgen deprivation therapy (ADT) alone, then from Oct 2015 onwards, the use of docetaxel (D) was authorized as part of SOC (at the investigator’s discretion until 2017, then, following the publication of LATITUDE and STAMPEDE trials, accrual was restricted to men receiving ADT+ D). Efficacy and safety in OM included in PEACE-1 were analyzed with the same methods used in the overall trial (Lancet 2022; 399: 1695-1707). Results: A total of 741 younger men (YM) (63%) and 431 OM (37%) were randomized. OM presented with more altered PS (ECOG 1-2) (36% vs 26% p=0.0003) and less frequent use of docetaxel (D) as part of SOC (66% vs 51% p<0.0001) than YM. Hypertension (56,5% vs 38,2%, p<0,001) and diabetes mellitus type 2 (15,5% vs 11%, p=0,029) were significantly more frequent in OM. Median time to AAP discontinuation was shorter (30.0 months [95%CI= 22.1; 35.4] vs 41.4 [95%CI= 31.5; 54.0] independently of D use and more frequently due to adverse events or death in the older than younger population. The benefit of AAP on radiographic progression-free survival (rPFS) tended to decrease with age in the overall population: (HR 0.65, 95%CI 0.42-1.01) in OM vs (HR 0.49, 95%CI 0.35-0.69) for YM. The same trend was observed on overall survival (OS): (HR 0.95, 95%CI 0.72-1.25) for OM vs (HR: 0.73, 95%CI 0.58-0.92) for YM. On the other hand, in men fit to receive the SOC composed of ADT+D, the rPFS benefit of AAP was comparable in OM (HR 0.55, 95%CI 0.29-1.04) and in YM (HR 0.5, 95%CI 0.33-0.78). The OS benefit of AAP was: (HR 0.80, 95%CI 0.53-1.2) and (HR 0.71, 95%CI 0.52-0.95) in OM and YM, respectively. Safety data show that severe adverse events (grade 3-5) were more frequent in OM receiving AAP in comparison with YM (69% vs 61%) while there was no difference between older and YM not receiving AAP (48% vs 47%). Conclusions: This post-hoc analysis of PEACE-1 suggests that, in the overall population, OM derive a lower benefit, both in terms of rPFS and OS, from adding AAP to SOC versus YM. This decreased benefit is likely due to more toxicity leading to more frequent and earlier drug discontinuation. Importantly, in OM fit enough to receive ADT+D, the benefit of adding AAP to SOC was comparable to YM. Clinical trial information: NCT01957436 .

Dosing, safety, and pharmacokinetics (PK) of combination therapy with darolutamide (DARO), androgen-deprivation therapy (ADT), and docetaxel (DOC) in patients with metastatic hormone-sensitive prostate cancer (mHSPC) in the ARASENS study

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Background: In ARASENS (NCT02799602), DARO in combination with ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI 0.57–0.80; P<0.001) vs placebo (PBO) + ADT + DOC in patients with mHSPC. Incidences of treatment-emergent adverse events (TEAEs) were similar between treatment groups. We report dosing, safety, and PK of coadministration of DARO and DOC with ADT. Methods: Patients with mHSPC were randomized 1:1 to DARO 600 mg twice daily or PBO, plus ADT and DOC (75 mg/m2 q21d for 6 cycles). The effect of DARO on DOC PK was assessed by noncompartmental analysis from the first 25 patients with dense PK data and by population PK (PopPK) for all patients. DARO PK from ARASENS were compared with PK data from ARAMIS (NCT02200614; without DOC) to evaluate the impact of DOC on DARO PK. Results: Of 1306 randomized patients, 1305 were included in the full analysis set (DARO, n=651; PBO, n=654). The median treatment duration was longer with DARO vs PBO (41.0 vs 16.7 months) and more DARO-treated patients (45.9% vs 19.1%) were still receiving treatment at primary analysis cutoff (Oct 25, 2021). Almost all patients completed 6 cycles of DOC in both groups (DARO, 87.6%; PBO, 85.5%). The proportion of patients requiring DOC dose modification (interrupted/delayed or reduced) was similar between groups (DARO, 60.0%; PBO, 62.9%). TEAEs led to discontinuation/reduction of DOC in 8.0%/19.9% of DARO patients and 10.3%/19.5% of PBO patients. PopPK analysis indicated that DOC PK in ARASENS was generally consistent with that in the literature. A slight numeric increase in DOC exposure was observed in the DARO + DOC + ADT arm, with 15% higher maximum plasma concentration (geometric mean, 1.93 vs 1.68 µg/mL) and 6% higher area under the concentration-time curve (AUC0-tlast within an 8-hour sampling interval, 2.10 vs 1.99 µg·h/mL) vs PBO + DOC + ADT. This small numeric increase is likely not clinically relevant given the variability in DOC exposure (coefficient of variation, 23%–54%). PK meta-analysis of ARASENS and, which considered patients’ intrinsic characteristics as covariates (eg, age, body weight, region), indicated a 10% lower AUC0-12ss of DARO in patients receiving DOC vs those not receiving DOC, which is not considered clinically relevant. Conclusions: The combination of DARO + DOC + ADT increases overall survival with similar overall incidence of TEAEs and no observed drug-drug interactions between DARO and DOC. DARO can be effectively and safely administered with DOC in patients with mHSPC without clinically relevant changes in PK of DARO or DOC. Clinical trial information: NCT02799602 .

Association of prostate-specific antigen (PSA) response and overall survival (OS) in patients with metastatic hormone-sensitive prostate cancer (mHSPC) from the phase 3 ARASENS trial

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Background: Reductions in PSA level have been associated with improved OS in patients (pts) with mHSPC. In ARASENS (NCT02799602), darolutamide (DARO) + androgen-deprivation therapy (ADT) in combination with docetaxel significantly reduced the risk of death by 32.5% (hazard ratio [HR] 0.675; 95% confidence interval [CI] 0.568–0.801; P< 0.0001) vs ADT + docetaxel in pts with mHSPC. We report the association between PSA response and OS from ARASENS. Methods: Pts with mHSPC were randomized 1:1 to DARO 600 mg twice daily or matching PBO + ADT and docetaxel. Serum PSA was measured at screening and every 12 weeks. Exploratory analyses included time to PSA progression (≥25% increase from PSA nadir [lowest or at study entry] and PSA increase ≥2 ng/mL ≥12 weeks from nadir [both confirmed by a second value ≥3 weeks later]) and undetectable PSA (< 0.2 ng/mL for 2 samples ≥3 weeks apart) at 24, 36, and 52 weeks and any time during treatment. Comparisons between treatment groups were performed using the Cochran-Mantel Haenszel test stratified by randomization stratification factors (metastatic spread according to TNM classification and alkaline phosphatase levels at study entry). Post hoc landmark analyses evaluated the association between undetectable PSA at weeks 24 and 36 and OS for the overall population. Results: Of 1306 randomized pts, 1305 were included in the full analysis set (DARO 651; PBO 654), both with ADT and docetaxel. Median (range) PSA levels at study entry were 30.3 (0.0–9219.0) and 24.2 (0.0–11,947.0) ng/mL, respectively. DARO significantly prolonged time to PSA progression (HR 0.255; 95% CI 0.208–0.313; P< 0.0001). Undetectable PSA was achieved in more pts receiving DARO (48.7%) vs PBO (23.9%) at 24 weeks, and the rate continued to increase at 36 and 52 weeks in the DARO group to 57.1% and 60.2%, respectively, vs minimal change in the PBO group (25.1% and 26.1%). Undetectable PSA levels at any time were achieved in 67.3% in the DARO group and 28.6% in the PBO group. A treatment difference in undetectable PSA based on non-overlapping 95% CIs was observed at all time points. For the overall population, OS was improved for pts who achieved undetectable PSA levels vs those who did not at 24 weeks (HR 0.398; 95% CI 0.321–0.493) and 36 weeks (HR 0.351; 95% CI 0.284–0.434). Additional baseline and safety data by PSA level will be reported. Conclusions: The combination of DARO + ADT and docetaxel significantly prolonged the time to PSA progression and more pts receiving DARO vs PBO achieved undetectable PSA levels, reflecting strong PSA response over time. In pts with mHSPC, achievement of undetectable PSA at 24 and 36 weeks was associated with improved OS, with risk of death reduced by 60% and 65%, respectively, vs those who did not achieve undetectable PSA at 24 and 36 weeks. Clinical trial information: NCT02799602.

Patient preferences for treatment and outcomes in hormone-sensitive prostate cancer (HSPC)

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Background: Treatment options for patients with HSPC have broadened, and data regarding patient preferences for therapies can aid in therapeutic decision-making. This study evaluated the impact of attributes associated with therapies for US patients with locally advanced prostate cancer (LAPC) or metastatic HSPC (mHSPC) from the perspective of patient preferences. Methods: An online discrete choice experiment (DCE) was developed for patients with LAPC or mHSPC. The DCE included 12 questions designed to systematically require tradeoffs between treatment attributes of efficacy (5-year overall survival [OS]), tolerability (fatigue, skin rash, neurotoxicity, and common chemotherapy-related toxicity), and convenience (administration factors [route, frequency, and setting], concomitant use of steroids, and monitoring requirements). Respondents could choose androgen deprivation therapy (ADT) alone or with hypothetical therapies that improved 5-year OS but had additional adverse events (AEs). Attribute-specific importance weights measuring their relative impact on treatment choices were estimated using a mixed-logit model, which also controlled for heterogeneity in preferences. Results: From September 3 to October 14, 2021, 82 respondents (mean age 61 years) completed the survey (LAPC, n = 40; mHSPC, n = 42), with 61 (74.4%) receiving ADT at the time of the survey. Respondents reported treatment efficacy (36% [95% confidence interval (CI) 22, 49]) as the most important aspect of treatment choice, followed by changes in chemotherapy-related toxicity (13% [95% CI 3, 22]) and the need for concomitant steroid use (12% [95% CI 5, 19]). Respondents considered monitoring requirements (8% [95% CI 5, 19]) to be more important than fatigue (5% [95% CI 2, 13]). Administration factors were comparable in importance to therapy AEs (Table). Respondents preferred, by at least 10 percentage points, adding therapies to ADT that could improve 5-year OS, at the detriment of additional AEs. Conclusions: After efficacy, convenience was considered to impact treatment choices at a rate comparable to tolerability issues, potentially influenced by perceived COVID-19 exposure risks. Patients with LAPC and mHSPC prioritize efficacy despite the detriment of additional AEs.[Table: see text]

Patient (pt) population and radiation therapy (RT) type in the long-term phase 3 double-blind, placebo (PBO)-controlled ATLAS study of apalutamide (APA) added to androgen deprivation therapy (ADT) in high-risk localized or locally advanced prostate cancer (HRLPC)

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Background: Current management of HRLPC includes long-term ADT with primary RT. Despite definitive primary treatment, these pts have a high risk of metastasis and death. The phase 3 ATLAS study (NCT02531516) is investigating whether treatment intensification with the addition of APA to neoadjuvant and adjuvant treatment with gonadotropin-releasing hormone agonist (GnRHa) and external beam radiation therapy (EBRT) will improve metastasis-free survival (MFS) in high-risk pts. Here we describe (1) the distribution of baseline characteristics in this high-risk pt population and (2) the application of different RT regimens reflecting recent international guidelines and clinical practice changes for pts with HRLPC. Methods: Eligible HRLPC pts (Gleason score [GS] ≥ 8 or 7 and prostate-specific antigen [PSA] ≥ 20 ng/mL and stage ≥ cT2c), with ECOG PS 0/1 and Charlson Comorbidity Index (CCI) ≤ 3 are stratified by GS, pelvic nodal status, use of brachytherapy boost, and region; pts are randomized 1:1 to APA or PBO plus GnRHa for 30 (28-d) treatment cycles. Study treatment is applied neoadjuvant/concurrent to RT with APA 240 mg/d vs bicalutamide 50 mg/d for 4 cycles; another 26 cycles are completed adjuvantly after RT with APA 240 mg/d vs PBO. Primary end point is MFS (time from randomization to first distant metastasis on CT/MRI/bone scan by independent central review blinded to treatment or death from any cause). Imaging is conducted at baseline and q6m from biochemical failure until MFS. The protocol has been amended to include PET imaging (PSMA, fluciclovine, or choline). Results: Pts (N = 1503) were randomized at 266 sites in 24 countries in North America, Latin America, Europe, and Asia. The study is fully enrolled, but ongoing. Baseline characteristics for the total population: median age, 67 yrs; ECOG PS 0/1; 89%/11%; tumor classification at study entry: high-risk, 66%/very high–risk, 34%; median PSA, 6.3 ng/mL; cT2, 44%/cT3, 50%; cN1, 13%. In 90% of ATLAS pts, RT used was standard EBRT to prostate/pelvis over 6-8 weeks (cumulative 78-81 Gy); in 10%, recent hypofractionation schedules (per CHHiP or NRG/RTOG 0415) were applied (20x3 Gy/d or 28x2.5 Gy/d). 5.6% of pts had EBRT combined with brachytherapy (per ASCENDE-RT). Conclusions: Baseline characteristics of the ATLAS study population are reflective of pts with high- and very high–risk features and pelvic nodal involvement undergoing primary RT in clinical practice. The RT schedules applied reflect recent evidence and guideline changes for the use of hypofractionation in this pt population. ATLAS is an example of how RT can be included in phase 3 trials of HRLPC, in combination with next-generation androgen receptor inhibitors (eg, APA). Clinical trial information: NCT02531516.

Alkaline phosphatase (ALP) decline and overall survival (OS) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) treated with radium-223 (Ra-223) in the REASSURE study

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Background: Ra-223 extends OS in pts with mCRPC. Predictive markers of response to Ra-223 are needed to help select pts who would benefit most from Ra-223 therapy. The ALSYMPCA study suggested a correlation between ALP decline and longer OS. Here, we evaluated whether ALP decline is associated with OS in the global real-world REASSURE study. Methods: Pts treated with Ra-223 were grouped by baseline ALP ≤147 U/L vs >147 U/L and any ALP decline vs no decline at week 12 from the first Ra-223 dose. The 147 U/L cut-off was selected based on the highest upper limit of normal for ALP from literature. Pts with a trend of decreasing ALP at closest value to week 12 between weeks 8 and 16 were included in the any decline group. Association of ALP decline with OS was assessed in the ≤147 U/L and >147 U/L groups separately. Median OS is provided with an unadjusted hazard ratio (HR) (95% confidence interval [CI]). Multivariate Cox models provided adjusted HRs (95% CI) for the association of ALP decline with OS. Some baseline covariates were not included in the models due to missing data. Results: 785 of 1465 pts had baseline ALP measurements, of whom 779 had week 12 ALP measurements: 443 had ≤147 U/L and 336 >147 U/L. In the ≤147 U/L group, median OS was 23.0 months (m) (95% CI 20.9–25.7) in pts with ALP decline (n=329) and 16.4 m (95% CI 14.1–20.4) in pts with no decline (n=114). In the >147 U/L group, median OS was 12.9 m (95% CI 11.7–14.3) in pts with ALP decline (n=295) and 8.1 m (95% CI 5.6–10.3) in pts with no decline (n=41). Comparison of unadjusted and adjusted HRs is shown in the Table. Conclusions: Pts with an ALP decline in first 12 weeks of Ra-223 treatment had longer OS. The effect of other baseline variables, including age, PSA, Hgb and prior treatments, provided adjustment but did not change this outcome. [Table: see text]

Defining more precisely the effects of docetaxel plus ADT for men with mHSPC: Meta-analysis of individual participant data from randomized trials

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Background: Adding docetaxel to androgen deprivation therapy(ADT) improves survival in metastatic, hormone-sensitive prostate cancer (mHSPC), but uncertainty remains about who benefits most. To investigate this thoroughly and reliably, the STOPCAP M1 collaborationconducted a meta-analysis of individual participant data (IPD) from relevant trials. Methods: Methods were included in a registered protocol ( CRD42019140591 ). Updated IPD from the GETUG-15, CHAARTED and STAMPEDE trials were harmonised and checked. The main outcomes were overall survival (OS), progression-free survival (PFS) and failure-free survival (FFS). Overall pooled effects were estimated using intention-to-treat, 2-stage, fixed-effect meta-analysis, adjusted for age, PSA, Gleason sum score, performance status, and timing of metastatic disease (missing covariate values imputed), with 1-stage and random-effects sensitivity analyses. We assessed subgroup effects using 2-stage, fixed-effect meta-analysis of within-trial interactions, adjusted for the same covariates. We based these on PFS to maximise power, and OS whenever interactions were found. To explore multiple subgroup interactions, and to derive subgroup-specific absolute treatment effects, we used 1-stage, flexible parametric modelling and standardisation. Results: We obtained IPD for all 2261 men randomised, with median FU of 6 years (all patients). There were clear relative benefits of docetaxel on OS (HR = 0.79, 95% CI 0.70 to 0.88, p<0.0001), PFS (HR = 0.70, 95% CI 0.63 to 0.77, p<0.0001) and FFS (HR = 0.64, 95% CI 0.58 to 0.71, p<0.0001). With evidence of non-proportional hazards, we also estimated 5-year absolute differences: OS 10% (95% CI 6 to 15%), PFS 9% (95% CI 5 to 13%) and FFS 9% (95% CI 6 to 12%). The relative effect of docetaxel on PFS differed by volume of metastases (interaction p=0.027; high volume HR = 0.60, 95% CI 0.52 to 0.68; low volume HR = 0.78, 95% CI 0.64 to 0.94), and timing of metastatic disease (interaction p=0.077; synchronous HR = 0.67, 95% CI 0.60 to 0.75; metachronous HR = 0.89, 95% CI 0.67 to 1.18). OS results were similar. When metastatic disease volume and timing were combined, docetaxel appeared to improve PFS and OS for all men, except those with low volume, metachronous disease (Table). Conclusions: This IPD meta-analysis provides the most detailed assessment of the effects of docetaxel for mHSPC, and suggests that men with low volume, metachronous disease should be managed differently to those with other types of metastatic disease. [Table: see text]

Bone mineral density in men with de novo metastatic castration-sensitive prostate cancer treated with or without abiraterone plus prednisone in the PEACE-1 phase 3 trial

19

Background: Addition of abiraterone plus prednisone (AAP) to androgen deprivation therapy (ADT) with or without docetaxel (D) improved overall survival in men with de novo metastatic castration sensitive prostate cancer in PEACE-1 trial. An analysis of bone mineral density (BMD) was planned by an amendment in the last randomized patients to assess whether addition of AAP increases bone loss. Methods: Patients (pts) were randomized to receive either ADT + D + AAP or ADT + D (and also randomized for radiotherapy given to the prostate). BMD (g/cm2) of the lumbar spine (L), femoral neck (F) and total hip (H) were measured by dual x-ray absorptiometry at baseline, M6, M12 and M24 in both arms. Mean percent change in BMD values from baseline to the different time points were calculated. T-Scores were also assessed. Results: Among the 210 pts with BMD data, 182 (87%) had available data at baseline, 109 (52%) at M6, 94 (45%) at M12, and 109 (52%) at M24: 97 pts were treated with AAP and 98 without. In both arms, the median age was 65 years and 69 pts (71%) were ECOG PS 0. Median body mass index (BMI) was 25.6 and 26.5 kg/m2 in pts treated with or without AAP, respectively. BMD, T score and mean percent change in BMD values are summarized in the Table. Conclusions: This is the first prospective assessment of BMD in a randomized trial, according to an experimental treatment with AAP. Despite a bone loss increase in both arms over time, addition of AAP to ADT+D was associated with no or modest difference in bone loss during the first 2 years, compared to ADT+D. Data including fractures will be presented. Main limitations include the difficulty to reliably assess BMD in men with bone metastases, the limited sample size and the short follow-up (i.e. 2 years). Clinical trial information: NCT01957436. [Table: see text]

Overall survival with darolutamide versus placebo in combination with androgen-deprivation therapy and docetaxel for metastatic hormone-sensitive prostate cancer in the phase 3 ARASENS trial

13

Background: Darolutamide (DARO) is a structurally distinct and highly potent androgen receptor inhibitor that demonstrated improved overall survival (OS) and metastasis-free survival vs placebo (PBO) and a low incidence of treatment-emergent adverse events (TEAEs) in patients (pts) with nonmetastatic castration-resistant prostate cancer (CRPC). We investigated whether DARO in combination with standard androgen-deprivation therapy (ADT) + docetaxel would increase OS in pts with metastatic hormone-sensitive prostate cancer (mHSPC) in the ARASENS study (NCT02799602). Methods: This international, double-blind, phase 3 study enrolled pts with mHSPC and ECOG PS 0/1 who were randomized 1:1 to DARO 600 mg twice daily or matching PBO in addition to ADT + docetaxel. Randomization was stratified by extent of disease according to TNM (M1a vs M1b vs M1c) and alkaline phosphatase levels ( < vs ≥ upper limit of normal). The primary endpoint was OS. Secondary efficacy endpoints included time to CRPC, time to pain progression, time to first symptomatic skeletal event (SSE), and time to initiation of subsequent systemic antineoplastic therapies. Safety was also assessed. Results: From Nov 2016 to June 2018, 1306 pts were randomized, 651 to DARO and 655 to PBO, in combination with ADT + docetaxel. Median age was 67 y in both arms. At the primary data cutoff (Oct 25, 2021), DARO significantly decreased the risk of death by 32.5% vs PBO (HR 0.675, 95% CI 0.568–0.801; P < 0.0001). The significant improvement in OS was observed even though substantially more pts received subsequent life-prolonging systemic antineoplastic therapy in the PBO arm (75.6%) vs the DARO arm (56.8%). The significant OS benefit was consistent across prespecified subgroups. In addition, DARO significantly delayed time to CRPC versus PBO (HR 0.357, 95% CI 0.302–0.421; P < 0.0001). Time to pain progression was also significantly longer with DARO vs PBO (HR, 0.792, 95% CI 0.660–0.950; P= 0.0058), as were time to first SSE and time to initiation of subsequent systemic antineoplastic therapy. TEAEs were similar between treatment arms, and the incidences of the most common TEAEs (≥10%) were highest during the overlapping docetaxel treatment period for both arms, with grade 3/4 TEAEs of 66.1% for DARO and 63.5%for PBO, mainly due to neutropenia (33.7% vs 34.2%, respectively). TEAEs led to treatment discontinuation in 13.5% of pts in the DARO arm and 10.6% of pts in the PBO arm. Conclusions: In pts with mHSPC, early treatment combining DARO with ADT + docetaxel significantly increased OS and improved key secondary endpoints vs ADT + docetaxel alone. The incidence of TEAEs was similar in the two treatment arms. Clinical trial information: NCT02799602.

Testosterone recovery for relugolix versus leuprolide in men with advanced prostate cancer: Results from the phase 3 HERO study

104

Background: In the phase 3 HERO study, the oral GnRH receptor antagonist, relugolix, showed sustained testosterone suppression superior to that of leuprolide (96.7% vs 88.8%; difference: 7.9% [95% CI, 4.1 to 11.8; P < 0.001]). Herein, we provide an analysis of the testosterone recovery data in a subgroup of 184 men from the HERO study who were not indicated to continue androgen deprivation therapy. Methods: The phase 3 HERO study was designed to evaluate relugolix in men with advanced prostate cancer. Overall, 934 men were randomized 2:1 to receive relugolix 120 mg orally once daily after a single oral loading dose of relugolix 360 mg on Day 1 or leuprolide injections every 12 weeks for 48 weeks. Testosterone recovery was assessed in 184 patients who completed 48 weeks of treatment and who did not plan to start alternative androgen deprivation therapy within the following 12 weeks (or within 24 weeks following the last injection of leuprolide 3-month depot). During the 90-day recovery period, assessments included time to testosterone recovery (≥ 280 ng/dL, the lower limit of the normal range) using the Kaplan-Meier method, PSA concentrations in testosterone recovery phase, and adverse events during the recovery phase. All analyses were conducted in a modified intent to treat population. Results: Overall, 137 men in the relugolix group and 47 men in the leuprolide group were included in these analyses. Mean (standard deviation) testosterone levels for men entering the recovery assessment were 427±142 ng/dL and 404±127 ng/dL in the relugolix and leuprolide groups, respectively. The cumulative incidence rate of testosterone recovery to ≥280 ng/dL at 90 days after drug discontinuation was 53.9% in the relugolix group compared with 3.2% in the leuprolide group (nominal p = 0.0017). Overall, 74 of the 137 men in relugolix group recovered testosterone with a median time to recovery of 86.0 days (95% CI: 65.0, 92.0), versus 2 of the 47 men in leuprolide group with a median time to recovery of 112.0 days (95% CI: 112.0, not estimable). At the 90-day follow-up visit, the median PSA values were 0.39 ng/mL (range: 0 to 233.1) and 0.06 ng/mL (0 to 14.0) in the relugolix and leuprolide groups, respectively. Incidence of adverse events were generally similar in the treatment groups during the recovery phase, with 96% of men experiencing at least one adverse event and 15% of men experiencing a grade ≥3 adverse event in both treatment groups during the recovery phase. Conclusions: Relugolix, an oral nonpeptide GnRH receptor antagonist, had a faster and more complete recovery of testosterone to normal levels after treatment discontinuation versus leuprolide in a subgroup of men from the phase 3 HERO study. Clinical trial information: NCT03085095.

Overall Survival in Men With Bone Metastases From Castration-Resistant Prostate Cancer Treated With Bone-Targeting Radioisotopes: A Meta-analysis of Individual Patient Data From Randomized Clinical Trials

Importance

Both α-emitting and β-emitting bone-targeted radioisotopes (RIs) have been developed to treat men with metastatic castration-resistant prostate cancer (CRPC). Only 1 phase 3 randomized clinical trial has demonstrated an overall survival (OS) benefit from an α-emitting RI, radium 223 (223Ra), vs standard of care. Yet no head-to-head comparison has been done between α-emitting and β-emitting RIs.

Objective

To assess OS in men with bone metastases from CRPC treated with bone-targeted RIs and to compare the effects of α-emitting RIs with β-emitting RIs.

Data Sources

PubMed, Cochrane Library, ClinicalTrials.gov, and meeting proceedings between January 1993 and June 2013 were reviewed. Key terms included randomized trials, radioisotopes, radiopharmaceuticals, and prostate cancer. Data were collected, checked, and analyzed from February 2017 to October 2018.

Study Selection

Selected trials included patients with prostate cancer, recruited more than 50 patients from January 1993 to June 2013, compared RI use with no RI use (placebo, external radiotherapy, or chemotherapy), and were randomized. Patients were diagnosed with histologically proven prostate cancer and disease progression after both surgical or chemical castration and have evidence of bone metastasis. Nine randomized clinical trials were identified as eligible, but 3 were excluded for insufficient data.

Data Extraction and Synthesis

Individual patient data were requested for each eligible trial, and all data were checked with a standard procedure. The log-rank test stratified by trial was used to estimate hazard ratios (HRs), and a similar fixed-effects (FE) model was used to estimate odds ratios (ORs). The between-trial heterogeneity of treatment effects was evaluated by Cochran test and I2 and was accounted by a random-effects (RE) model.

Main Outcomes and Measures

Overall survival; secondary outcomes were symptomatic skeletal event (SSE)-free survival and adverse events.

Results

Based on 6 randomized clinical trials including 2081 patients, RI use was significantly associated with OS compared with no RI use (HR, 0.86; 95% CI, 0.77-0.95; P = .004) with high heterogeneity (χ25 = 24.46; P < .001; I2 = 80%), but this association disappeared when using an RE model (HR, 0.80; 95% CI, 0.61-1.06; P = .12; τ2 = 0.08). The heterogeneity is explained both by the type of RI and by the inclusion of 2 outlier trials that included 275 patients; the OS benefit was significantly higher with the α-emitting RI 223Ra (HR, 0.70; 95% CI, 0.58-0.83) but not significant with the β-emitting RI strontium-89 (HR, 0.96; 95% CI, 0.84-1.10) (P for interaction = .004). Excluding the outlier trials led to an overall HR of 0.82 (95% CI, 0.73-0.92; P < .001) (between-trial heterogeneity: χ23 = 6.51; P = .09; I2 = 54%) using an FE model and an HR of 0.80 (95% CI, 0.65-0.99; P = .04; τ2 = 0.02) using an RE model. The HR for SSE-free survival was 0.81 (95% CI, 0.69-0.93; P = .004) (between-trial heterogeneity: χ23 = 6.71; P = .08; I2 = 55%) when using an FE model and was 0.76 (95% CI, 0.58-1.01; P = .06; τ2 = 0.04) when using an RE model. There were more hematological toxic effects with RI use compared with no RI use (OR, 1.48; 95% CI, 1.17-1.88; P = .001).

Conclusions and Relevance

In metastatic CRPC, a significant improvement of OS and SSE-free survival was obtained with bone-targeted α-emitting but not β-emitting RIs. Caution is necessary for generalizability of these results, given the between-trial heterogeneity.

Safety and overall survival (OS) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) treated with radium-223 (Ra-223) plus subsequent taxane therapy

5542

Background: Ra-223, a targeted alpha therapy, showed a survival benefit and favorable safety profile over 3 years’ (yrs) follow-up in mCRPC pts (ALSYMPCA trial). REASSURE (NCT02141438) is a global, prospective, single-arm, observational study of long-term Ra-223 safety in routine clinical practice in mCRPC pts (planned 7-yr follow-up). Methods: This analysis, based on the second prespecified interim analysis (data cutoff 3-20-2019) of REASSURE (N = 1465), evaluated safety/OS in the pt subset that was chemotherapy-naïve at Ra-223 administration but received subsequent taxane therapy any time after Ra-223 completion. Results: 182 pts received taxane therapy after Ra-223. Most (58%) had unresected primary tumors, 69% had ≥6 metastases, 99% received prior systemic anticancer therapy (Table). 143 (79%) completed 5 or 6 Ra-223 injections. Subsequent anticancer therapies included docetaxel (95%), enzalutamide (25%), cabazitaxel (24%), abiraterone (12%), lutetium-177-prostate-specific membrane antigen (4%), and sipuleucel-T (1%). During/up to 30 days after taxane therapy, 15 pts (8%) had grade 3/4 hematologic adverse events: anemia (erythropenia) (n = 11, 6%), neutropenia (n = 3, 2%), and thrombocytopenia (n = 2, 1%). Median OS was 24.3 (95% CI: 20.9–27.5) months from Ra-223 initiation and 11.8 (95% CI: 10.6–14.1) months from subsequent taxane initiation. Conclusions: In this cohort where Ra-223 was integrated prior to taxane therapy, most pts received multiple subsequent anticancer therapies. It appears that sequencing of multiple treatment modalities with different mechanisms of action may contribute to improved OS. Taxane therapy in routine clinical practice in pts previously treated with Ra-223 had acceptable hematologic safety/tolerability profiles. Clinical trial information: NCT02141438 . [Table: see text]

HERO phase III trial: Results comparing relugolix, an oral GnRH receptor antagonist, versus leuprolide acetate for advanced prostate cancer

5602

Background: LHRH agonists are the mainstay for medical castration in advanced prostate cancer; however, they cause an initial testosterone (T) surge with a delayed onset of castration and require depot injection. Relugolix is the first oral GnRH receptor antagonist, which was previously shown to rapidly suppress T levels. The HERO trial compared the safety and efficacy of relugolix with leuprolide acetate in advanced prostate cancer patients. Methods: HERO is a 48-week, global, pivotal phase III trial that randomized 934 patients with androgen-sensitive advanced prostate cancer in a 2:1 ratio to receive relugolix 120 mg orally QD after a single l or leuprolide acetate 3-month depot injection. The primary endpoint was to achieve and maintain serum T suppression to castrate levels (< 50 ng/dL) through 48 weeks. Key secondary endpoints included castration rates at Day 4, profound castration (< 20 ng/dL) rates at Days 4 and 15, PSA response rate at Day 15 and FSH levels at Week 25. Testosterone recovery was evaluated in a subset of 184 patients. Results: A total of 96.7% (95% CI: 94.9%, 97.9%) of men on relugolix achieved and maintained castration through 48 weeks compared to 88.8% on leuprolide. The difference of 7.9% (95% CI: 4.1%, 11.8%) demonstrated non-inferiority (margin -10%) and superiority (P < 0.0001) of relugolix to leuprolide. All key secondary efficacy endpoints tested demonstrated superiority over leuprolide (P < 0.0001) (Table). In the testosterone recovery subset, median T levels were 270.76 ng/dL in the relugolix compared to 12.26 ng/dL in the leuprolide group 90 days after discontinuation of therapy. In a prespecified analysis, the incidence of major adverse cardiovascular events (MACE) was lower in the relugolix group than in the leuprolide group (2.9% vs. 6.2%, respectively); otherwise the safety and tolerability profiles were generally similar. Conclusion: Relugolix achieved castration as early as Day 4 and demonstrated superiority over leuprolide in sustained T suppression through 48 weeks, faster T recovery after discontinuation and a 50% reduction in MACE. Relugolix has the potential to become a new standard for T suppression for patients with advanced prostate cancer. Clinical trial information: NCT03085095 . [Table: see text]

Efficacy and safety in older patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) receiving cabazitaxel (CBZ) versus abiraterone (ABI) or enzalutamide (ENZ) in the CARD study

5559

Background: In the CARD (NCT02485691) study, radiographic PFS (rPFS), PFS and OS were significantly improved with CBZ vs. androgen-signaling-targeted agents (ARTA; ABI or ENZ) in pts with mCRPC who had received docetaxel (DOC) and progressed within 12 months (mo) on an alternative ARTA. This analysis evaluated the impact of age (< 70 vs. ≥ 70 years) on the efficacy and safety of CBZ and ARTAs in CARD. Methods: 255 pts with mCRPC were randomized 1:1 to CBZ (25 mg/m2 IV Q3W + prednisone [P] + G-CSF) vs. ABI (1000 mg PO + P) or ENZ (160 mg PO) until disease progression, unacceptable toxicity or pt request. Pts were eligible if they had received ≥ 3 cycles of DOC and progressed ≤ 12 mo on the previous alternative ARTA. Primary endpoint was rPFS. Subgroup analysis of older (≥ 70 years; n = 135) and younger (< 70 years; n = 120) pts was pre-specified for rPFS; others were post hoc. Results: rPFS was significantly improved vs. ARTA in both older (median 8.2 vs. 4.5 mo; HR 0.58; 95% CI 0.38–0.89) and younger pts (median 7.4 vs. 3.2 mo; HR 0.47; 95% CI 0.30–0.74). Median OS for CBZ vs. ARTA was 13.9 vs. 9.4 mo (HR 0.66; 95% CI 0.41–1.06) in older pts and 13.6 vs. 11.8 mo (HR 0.66; 95% CI 0.41–1.08) in younger pts. PFS, tumor, PSA and pain responses also favored CBZ, regardless of age. Grade ≥ 3 adverse events (AEs) occurred in 57.8% vs. 49.3% of older pts receiving CBZ vs. ARTA and 48.4% vs. 42.1% in younger pts. AEs leading to death were more frequent with ARTA, mainly due to disease progression. Conclusions: CBZ had improved efficacy outcomes vs. ARTA in pts with mCRPC previously treated with DOC and the alternative ARTA, regardless of age. Grade ≥ 3 cardiac AEs were more frequent in older pts treated with ARTA. A higher rate of AEs was reported in older vs. younger pts, for ARTA and CBZ. CBZ and ARTA had different safety profiles in older compared with younger pts. Clinical trial information: NCT02485691 . Funding: Sanofi. [Table: see text]

CARD: Overall survival (OS) analysis of patients with metastatic castration-resistant prostate cancer (mCRPC) receiving cabazitaxel versus abiraterone or enzalutamide

5569

Background: The CARD trial (NCT02485691) compared cabazitaxel vs. an androgen receptor targeted agent (ART; abiraterone/enzalutamide) in mCRPC previously treated with docetaxel and the alternative ART (abiraterone/enzalutamide), in any order. These post hoc analyses assessed OS from various time points and the impact of prognostic factors. Methods: Patients with mCRPC previously treated with docetaxel and progressing ≤ 12 months on prior abiraterone/enzalutamide were randomized 1:1 to cabazitaxel (25 mg/m2 IV Q3W + daily prednisone + prophylactic G-CSF) vs. abiraterone (1000 mg PO + daily prednisone) or enzalutamide (160 mg PO). OS was calculated from date of diagnosis of metastatic disease, date of mCRPC, and start of 1st, 2nd or 3rd life-extending therapy (LET). A stratified multivariate Cox regression analysis assessed the impact of 14 prognostic factors on OS using a stepwise model selection approach with a significance level of 0.10 for entry into the model and 0.05 for removal. Results: In the CARD study (N = 255), median OS was longer with cabazitaxel vs. abiraterone/enzalutamide (13.6 vs 11.0 months; HR 0.64, 95% CI 0.46–0.89; p = 0.008). OS was numerically improved for cabazitaxel vs. abiraterone/enzalutamide when assessed from the time of diagnosis of metastatic disease or mCRPC, or from start of 1st or 2nd LET (Table). In the multivariate analysis, low hemoglobin, high baseline neutrophil to lymphocyte ratio, and high PSA values at baseline were associated with worse OS. In presence of these factors, the OS benefit observed with cabazitaxel versus abiraterone/enzalutamide remained significant (HR 0.63, 95% CI 0.42–0.94, p = 0.022). Conclusions: Cabazitaxel numerically improved OS vs. abiraterone/enzalutamide in patients with mCRPC previously treated with docetaxel and the alternative ART (abiraterone/enzalutamide), whatever the time point considered. The robustness of this OS benefit was confirmed by stratified multivariate analysis. Sanofi funded. Clinical trial information: NCT02485691 . [Table: see text]

Concurrent or layered treatment with radium-223 (Ra-223) and enzalutamide (Enza) or abiraterone plus prednisone/prednisolone (Abi/pred): A retrospective study of real-world clinical outcomes in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

5026

Background: In clinical practice, Ra-223 is often combined with Enza or Abi/pred. ERA 223 (NCT02043678) showed increased fracture risk with concurrent Ra-223+Abi/pred. We assessed real-world symptomatic skeletal events (SSEs) and overall survival (OS) of pts with mCRPC who received concurrent or layered Ra-223+Enza or Abi/pred. Methods: Patients with mCRPC treated with Ra-223 in US cancer clinics from 1/01/2013 to 6/30/2017 were identified from a Flatiron prostate cancer registry of electronic health records. Treatment initiation defined subgroups: concurrent (both started within 30 days) or layered (1 started ≥30 days after the other). Baseline (BL) was the first dose of Ra-223. Descriptive analysis was performed for BL characteristics, SSEs, and OS (Kaplan–Meier). Results: Of 625 pts treated with Ra-223, 48% received Ra-223+Enza or Abi/pred. Layered treatment was more common (73%) than concurrent (27%). BL characteristics and clinical outcomes were summarized [Table]. Conclusions: In a real-world setting, Ra-223+Enza or Abi/pred treatment was mainly layered. SSE rates with layered vs concurrent Ra-223+Abi/pred varied between subgroups; results must be treated cautiously given small pt numbers and a non-randomized study. The ongoing PEACE III trial is investigating concurrent Ra-223+Enza; a Phase III study (ESCALATE) exploring layered Ra-223+Enza is planned. [Table: see text]

Decreased fracture rate by mandating bone-protecting agents in the EORTC 1333/PEACE III trial comparing enzalutamide and Ra223 versus enzalutamide alone: An interim safety analysis

5007

Background: Skeletal fractures, pathological or not, are a frequent and underestimated side-effect of systemic treatment of metastatic castration resistant prostate cancer (mCRPC). The ERA223 trial (NCT02043678) was recently unblinded following the report of a significant increase in the fracture rates when abiraterone is combined with Ra223. Hence, FDA and EMA advised against this combination. The question whether mandated use of bone protecting agents (BPA), zoledronic acid or denosumab, would have mitigated the fracture risk and whether this risk also exists in the enzalutamide/Ra223 combination is presently unknown. Methods: The phase III EORTC-1333-GUCG/PEACEIII (NCT02194842) trial compares enzalutamide vs. a combination of Ra223 and enzalutamide in asymptomatic or mildly symptomatic mCRPC patients (https://www.eortc.org/research_field/clinical-detail/1333/). After the unblinding of ERA223, the trial was amended (v4.0, April 19, 2018) to mandate that all patients must start a BPA. We report the fracture rate in the safety population of 146 treated patients as of 28/01/2019. Results: Overall, 54.2% of the patients in the enza/Ra223 arm and 51.4% of the enza arm did not receive BPA; 18.0% in the enza/Ra223 arm and 27.0% in the enza arm did not use BPA at randomization, but started during protocol treatment according to the v4.0 amendment. 27.8% and 21.6% respectively, received BPA as of randomization. In total, 45.8% of enza/Ra223 patients and 48.6% of enza only patients receive bone protection on treatment. The fracture rate is reported in the table. Conclusions: There is a 13% risk of fracture with enzalutamide in asymptomatic mCRPC, in line with previous reports. This risk is significantly increased to 33% when Ra223 is added to enzalutamide. Strikingly, the risk is almost abolished by mandatory continuous administration of BPA starting at least 6 weeks before the first injection of Ra223, thus emphasizing the importance of treating mCRPC patients with BPA. Clinical trial information: NCT02194842. [Table: see text]

Association of plasma DNA repair deficient (DRD) status with clinical outcome of metastatic castration-resistant prostate cancer (mCRPC) patients (pts) treated with abiraterone acetate (AA) plus prednisone/dexamethasone (+P/D)

5066

Background: Somatic DRD deficiency in 15-30% of mCRPC pts have been observed and inhibition of enzyme poly ADP ribose polymerase (PARP) could prove beneficial. We aimed to define DRD status using plasma from pts treated on AA and evaluate associations with prospectively-collected outcome measures. Methods: Plasma DNA samples (128 baseline [BL], 134 cycle 2 day 1 [C2D1], 46 progression [PROG]) from chemotherapy-naïve mCRPC pts in a phase 2 study (NCT01867710) evaluating AA+P/D were subjected to custom target-capture next-generation sequencing. DRD assay was optimized and validated to detect pathogenic point mutations, small insertions/deletions, and copy number alternations (DRD+) in 8 DRD genes: BRCA1, BRCA2, FANCA, ATM, CHEK2, HDAC2, BRIP1, and PALB2. Analysis for genomic aberrations was a secondary exploratory objective. Associations with overall survival (OS), progression-free survival (PFS), and radiographic PFS (rPFS) were assessed using Cox regression models and Kaplan Meier analyses. Results: 11.7% of BL and 17.4% of PROG were DRD+. Bi-allelic was observed in 73.3% of BL DRD+ samples. Shorter PFS was observed in BL DRD+ vs DRD- (5.3 vs 15.5 mo; HR: 2.32; 95%CI:1.39-4.28; P < 0.002). Median PFS for BL DRD biallelic + vs DRD biallelic- was 5.1 vs 15.4 mo (HR: 2.49; 95% CI: 1.23-4.38; P < 0.0095). For multivariate analysis using DRD+, ALP, and LDH as covariates, DRD+ (HR: 2.1; 95% CI: 1.18-3.75; P < 0.012) and high ALP (HR: 1.66; 95% CI: 1.08-2.56; P < 0.021) were strongly associated with worse PFS. Median OS for BL DRD+ vs DRD- was 28.8 vs 41.3 mo (HR: 1.67; 95%CI:0.88-3.18; P = 0.116). Median rPFS for BL DRD+ vs DRD- was 16.2 vs 20.9 mo (HR: 1.64; 95%CI:0.83-3.21; P = 0.152). Of 39 Pts with BL, C2D1 and PROG samples, 3 were DRD+ (7.7%) at all 3 timepoints, 3 (7.7%) only at BL, 3 (7.7%) only at PROG (bi-allelic), 2 (5.1%) had extra deletion at PROG. Conclusions: Patients with mCRPC harboring DRD+ have worse outcomes with AA and represent a population with an unmet medical need.

Health-related quality of life (HRQoL) and pain progression with enzalutamide (ENZ) in metastatic hormone-sensitive prostate cancer (mHSPC) from the ARCHES study

5044

Background: The Phase 3 ARCHES trial (NCT02677896) evaluated the efficacy and safety of ENZ + androgen deprivation therapy (ADT) vs placebo (PBO) + ADT in 1150 men with mHSPC. Here we report patient-reported outcome (PRO) data using Functional Assessment of Cancer Therapy-Prostate (FACT-P) and Brief Pain Inventory Short Form (BPI-SF). Methods: FACT-P and BPI-SF were assessed at baseline (BL), week (wk) 13, and then every 12 wks until disease progression. Longitudinal changes were assessed using mean scores and mixed-model repeated measures; lower BPI-SF scores represent less pain/interference; higher FACT-P scores represent better HRQoL. Time from BL to first deterioration in PRO score was assessed by Kaplan-Meier estimates and Cox proportional hazards models. Clinically meaningful difference was defined by change from baseline ≥10 for FACT-P total and ≥2 for worst pain/severity. Results: PRO instrument completion rates were high (88−96%) up to wk 73. At BL, men in both arms were generally asymptomatic and reported good HRQoL (FACT-P total: ENZ + ADT, 113.9; PBO + ADT, 112.7) and low pain (worst pain [item 3]: ENZ + ADT, 1.80; PBO + ADT, 1.77). HRQoL and pain scores remained stable over time and there were no clinically meaningful differences between groups in change from BL to wk 73. The proportion of men with no change or improvement in PRO scores (67–88%) was similar in both groups at all time points up to wk 73. There was no significant difference between arms for time to deterioration in FACT-P total (HR 0.90 [95% CI] (0.74, 1.09); p = 0.2998). ENZ + ADT significantly delayed time to pain progression for worst pain (HR 0.82 [0.69, 0.98]; p = 0.0322) and pain severity (HR 0.79 [0.65, 0.97]; p = 0.0209) vs PBO + ADT. Conclusions: Men with mHSPC were generally asymptomatic and had high levels of HRQoL and low levels of pain at BL, likely due to most men initiating ADT several months prior to study entry. No clinically meaningful differences in HRQoL were observed between ENZ and PBO. The prolongation in radiographic progression-free survival observed with ENZ + ADT was accompanied by a significantly prolonged time to progression of worst pain and pain severity vs PBO + ADT. Clinical trial information: NCT02677896.

The role of bisphosphonates or denosumab in light of the availability of new therapies for prostate cancer

Most men with advanced prostate cancer will develop bone metastases, which have a substantial impact on quality of life. Bone metastases can lead to skeletal-related events (SREs), which place a burden on patients and healthcare systems. For men with castration-resistant prostate cancer (CRPC) and bone metastases, the treatment landscape has evolved rapidly over the past few years. The relatively recent approvals of the hormonal agents abiraterone acetate and enzalutamide, second-line chemotherapy cabazitaxel, and the radiopharmaceutical radium-223 dichloride (radium-223), have provided clinicians with a greater choice of treatments. These compounds have benefits in terms of overall survival based on the results of pivotal phase 3 studies. The bisphosphonate zoledronic acid and the RANK ligand inhibitor denosumab are indicated for the prevention of SREs in men with metastatic CRPC but studies of these compounds have not demonstrated a survival benefit. The important question of the role of bisphosphonates or denosumab in combination with these new agents has thus materialised. Current and emerging evidence from clinical studies of abiraterone acetate, enzalutamide and radium-223, suggest that addition of bisphosphonates or denosumab to these new therapies may provide further clinical benefits for patients with prostate cancer and bone metastases. This evidence may help to shape clinical practice but are based largely on post hoc analyses of clinical trial data. It is therefore apparent that further data are required from both clinical studies and real-world settings to enable physicians to understand the efficacy and safety of combination therapy with the new agents plus bisphosphonates or denosumab.

Intergroup study EORTC-1532-gucg: A phase 2 randomized open-label study of oral darolutamide (ODM-201) vs. androgen deprivation therapy (ADT) with LHRH agonists or antagonist in men with hormone naive prostate cancer (PCa)

TPS406

Background: Androgen deprivation therapy (ADT) by LHRH analogues aims to lower serum testosterone. ADT is associated with several side effects that include hot flushes, depression, loss of libido, metabolic disturbances leading to an increase risk of cardiovascular disease, increased bone resorption leading to increased risk of osteoporosis and skeletal fracture. AR antagonists may circumvent these side effects by suppressing AR transcription by competitive inhibition of AR, without lowering systemic testosterone. In Europe, first generation AR antagonists bicalutamide 150 mg is registered for the treatment of non-metastatic hormone-naïve PCa. is a novel AR antagonist that is structurally distinct with higher AR-binding affinity compared to bicalutamide, enzalutamide, and apalutamide. The aim of this trial is to investigate the activity, safety and tolerability of darolutamide as single agent, as an alternative to LHRH analogues in men requiring ADT. Methods: EORTC-1532-GUCG (NCT02972060) will randomize 250 men with hormone-naïve PCa 1:1 to 600 mg (2× 300-mg tablets) bid of darolutamide1 or LHRH agonist or antagonist, stratified for type of ADT (agonist vs. antagonist), disease extent (measurable, non-measurable, vs. no metastasis) and age (≥70 vs < 70 years). Key inclusion criteria include histologically confirmed asymptomatic PCa (all stages) for whom continuous ADT is indicated for a minimum period of 24 weeks. Patients with up to 4 confirmed not visceral metastases, are allowed. Baseline total testosterone should be ≥ 8 nmol/L or 230 ng/dL. Primary endpoint is PSA response assessed at 24 weeks, defined as a ≥ 80% decline in PSA at week 24 in the darolutamide study arm. The ADT arm is used as an internal non comparative control. Key secondary endpoints include: Change in hormone-treatment related symptoms scale of the EORTC QLQ-PR25 at 24 weeks (comparison between arms); objective response rate at 24 weeks in patients with measurable disease at baseline, safety according to NCI-CTC version 4.0. Clinical trial information: NCT02972060.

Randomised phase 3 trial of enzalutamide in androgen deprivation therapy (ADT) with radiation therapy for high risk, clinically localized prostate cancer: ENZARAD (ANZUP 1303)

TPS156

Background: Adjuvant ADT with an LHRH analog (LHRHA) given before, during and after radiotherapy (RT) is standard of care for high risk localised prostate cancer (PC). Enzalutamide improves overall survival (OS) in castration-resistant, metastatic prostate cancer. We hypothesized that the addition of enzalutamide to adjuvant ADT and RT will improve outcomes. The aim is to determine the effects of enzalutamide versus a conventional non-steroidal anti-androgen (NSAA) as part of neoadjuvant and adjuvant ADT in men undergoing RT for high risk, localized PC. Methods: DESIGN: Open label, randomised, phase 3 trial including ANZ, USA, UK, Ireland and Europe. ENDPOINTS: OS (primary), cause-specific survival, PSA progression free survival (PFS), clinical PFS, time to subsequent hormonal therapy, time to castration-resistant disease (PCWG2 criteria), metastasis free survival (MFS), adverse events and health-related quality of life (HRQOL). CORRELATIVE OBJECTIVES: identification of prognostic/predictive biomarkers from archival tumour tissue and serial blood samples. SAMPLE SIZE: 800 participants with a minimum follow-up of 5.5 yrs is designed to give 80% power to detect 33% reduction in the hazard of death assuming 5-year survival rate of 76% amongst controls. TREATMENT: Enzalutamide 160mg daily for 24 months versus conventional NSAA for 6 months. All participants receive LHRHA for 24 months, and RT starting about week 16 delivered as 78Gy in 39#, or 46Gy in 23# plus brachytherapy (nodal RT optional for N0, mandatory for N1). ASSESSMENTS: Baseline, then every 8 weeks until year 2, then 3-4 monthly until year 5, 6-monthly until year 7, then annually. Imaging with CT/MRI and bone scan at baseline, PSA progression, then 6 monthly until re-initiation of ADT, when PCWG2 criteria for CRPC are met and then 3 monthly until evidence of metastases. 623 participants recruited from 61 sites as of 16 October 2017. ENZARAD is an investigator-initiated cooperative group trial led by ANZUP Cancer Trials Group with funds and product from Astellas. Clinical trial information: NCT02446444.

ARASENS: A phase 3 trial of darolutamide in combination with docetaxel for men with metastatic hormone-sensitive prostate cancer (mHSPC)

TPS383

Background: The addition of either docetaxel or abiraterone acetate plus prednisone to androgen deprivation therapy (ADT) improves overall survival (OS) compared with ADT alone in men with mHSPC. It is hypothesized that other androgen receptor (AR)-targeted therapies could be combined with docetaxel for mHSPC. Darolutamide (ODM-201) is an investigational oral AR antagonist with a unique chemical structure and negligible blood-brain barrier penetration that inhibits tumor growth by binding to AR and AR mutants (eg, W742L and F877L) with high affinity and specificity. In phase 1/2 ARADES and phase 1 ARAFOR trials, darolutamide demonstrated antitumor activity and was well tolerated in men with metastatic castration-resistant prostate cancer (mCRPC). ARASENS will evaluate the addition of darolutamide to standard ADT and docetaxel in men with mHSPC. Methods: This international, randomized, double-blind, placebo-controlled phase 3 trial (NCT02799602) is being conducted at > 300 sites in 23 countries. ~1300 men with newly diagnosed mHSPC will be randomized 1:1 to darolutamide (600 mg orally twice daily) or matching placebo. All patients will receive standard ADT + docetaxel (6 cycles). Patients will be stratified by disease extent and alkaline phosphatase level. Key inclusion criteria: histologically or cytologically confirmed PC with documented metastases, started ADT ± first-generation antiandrogen therapy ≤12 weeks before randomization, and ECOG performance status 0-1. The primary end point is OS. Secondary end points include time to mCRPC, initiation of subsequent anticancer therapy, symptomatic skeletal event (SSE)-free survival, time to first SSE, first opioid use, pain progression, and worsening of physical symptoms. Safety will be assessed. ARASENS is actively enrolling at > 280 sites across 23 countries. Clinical trial information: NCT02799602.

Hepatic effects assessed by review of safety data in enzalutamide castration-resistant prostate cancer (CRPC) trials

199

Background: Androgen receptor inhibitor enzalutamide (ENZA) improves survival in patients with metastatic CRPC. As the liver is the main route of ENZA elimination, this post hoc analysis evaluated the hepatic effects of ENZA versus comparators in controlled CRPC trials. Methods: Safety data from two large Phase 3, placebo (PBO)- (PREVAIL, NCT0121299; AFFIRM, NCT00974311) and two smaller Phase 2, bicalutamide (BIC)-controlled (STRIVE, NCT01664923; TERRAIN, NCT01288911) ENZA trials in men with CRPC were assessed for hepatic impairment-related adverse events (AEs) using the following standardized narrow MedDRA queries V19.1: hepatic failure, fibrosis and cirrhosis, and other liver damage-related conditions; hepatitis, non-infectious; and liver-related investigation, signs, and symptoms. Liver-related laboratory test results were also evaluated. Data were summarized as follows: patients receiving ENZA in Phase 3 trials (n = 1671); patients receiving ENZA in Phase 2 trials (n = 380); patients receiving PBO (n = 1243); patients receiving BIC (n = 387); and combined ENZA-treated patients (n = 2051). Results: Percentages of hepatic impairment-related AEs ranged between 2.9% and 4.5% with ENZA, and were 2.7% with PBO and 5.4% with BIC (Table). The most common hepatic impairment-related AEs were increased aspartate (AST) and alanine aminotransferase (ALT; Table). Within each trial, the incidences of grade ≥3 AEs were similar, and dose reductions or discontinuations due to hepatic impairment-related AEs were low (Table). When adjusted for treatment exposure, AEs per 100 patient-years were lower with ENZA versus either PBO or BIC (Table). Conclusions: This combined analysis of CRPC trials demonstrates no hepatic safety signal with ENZA and thus routine liver tests are not required. Clinical trial information: NCT0121299; NCT00974311; NCT01664923; NCT01288911. [Table: see text]

A meta-analysis on individual data of bone-targeting radio-isotopes in men with bone metastases from castration-resistant prostate cancer

352

Background: Among bone-targeted radio-isotopes (RI), Radium-223 (an α-emitter) is the only one with clearly demonstrated overall survival (OS) benefit in men with castration-resistant prostate cancer (CRPC). The aim of this meta-analysis is to estimate the OS impact of RI in men with CRPC. Methods: An individual patient data meta-analysis was carried out from randomized trials with inclusion period 1993-2013. Eligible trials included more than 50 patients, mandated bone metastases from CRPC and randomly evaluated RI. Endpoints were OS (primary), symptomatic skeletal events (SSE) and toxicity. A fixed-effect model was used. The log-rank test stratified by trial was used to estimate individual and overall hazard ratios (HR). Subset analyses were performed by the type of radiation (α vs. β emission) and by trial comparison: RI + Chemotherapy (CT) vs. CT, RI+ External beam radiotherapy (EBRT) vs. EBRT, RI vs. EBRT. Results: From 9 identified trials, data from 6 trials comprising 2081 patients (min: 64, max: 921) were collected with 2 trials representing 80% of data. The data from 3 trials (n = 341) were not available. The overall effect on OS favoured RI with HR = 0.86 [0.77-0.95] but high heterogeneity between trials (p < 0.001, I2= 79.6%). The overall effect of α- emitters on OS (HR = 0.70 [0.58; 0.83], 2 trials, n = 985) significantly differed from that of β-emitters (HR = 0.96 [0.84; 1.10], n = 4 trials, n = 1096) (interaction p = 0.0041). The overall effect on SSE favoured RI with HR = 0.81 [0.69-0.93] (4 trials, n = 1806) with marked between trial heterogeneity (p = 0.08, I² = 55.3%) and a significant difference (p = 0.02) by the type of RI (α-emitters: HR = 0.65 [0.52-0.82]-2 trials, β-emitters: HR = 0.93 [0.77-1.13]-2 trials). Conclusions: In men with metastatic CRPC a significant improvement of OS and SSE was obtained with bone targeted α-emitter radio isotopes, but not with β-emitter. However, some between trial heterogeneity of effects on OS need further investigations.

Intergroup study EORTC-1333-GUCG: A randomized multicenter phase III trial comparing enzalutamide vs. a combination of Ra223 and enzalutamide in asymptomatic or mildly symptomatic castration resistant prostate cancer (CRPC) patients metastatic to bone (PEACE III)

TPS390

Background: α-emitting radiopharmaceutical Ra-223 reduces the risk of death by 30% vs placebo in phase 3 ALSYMPCA (Parker et al. NEJM 2013). Ra-223’s favourable safety profile and lack of significant toxicity support combining it with other agents. The ALSYMPCA trial was developed to add Ra-223 on the contemporary standard of care that did not include last generation AR pathway inhibitors enzalutamide, one of the modern reference treatments for asymptomatic or moderately symptomatic metastatic CRPC (Gillessen et al. Eur Urol. 2017). In addition Ra-223 is registered in symptomatic prostate cancer (PCa), a very late stage of modern patient disease. There is thus a good rationale to combine Ra-223 to modern AR pathway inhibitors and to initiate the treatment in asymptomatic or moderately symptomatic patients. Methods: The EORTC 1333-GUCG study will run in 51 sites (21 activated) across 7 European countries, 4 sites in US and 12 sites in Canada. The study is an intergroup initiative between EORTC (Coordinating Group), UNICANCER; Cancer Trials Ireland (Ireland), ACCRU (The United States), and CUOG (Canada). A total of 560 patients will be randomized in a 1:1 ratio to receive enzalutamide 160 mg q.d. p.o. or enzalutamide at the same dose and Ra223 at 55 kBq/kg i.v. monthly for 6 months. Patients will be stratified by country, pain (BPI 0-1 vs BPI 2-3), prior docetaxel use (no vs yes) and use of bone targeting agents (no vs yes). The main inclusion criteria require asymptomatic or mildly symptomatic (defined as no opioids and BPI-SF question 3 < 4), metastatic to bone with ≥ 2 bone metastases with or without additional lymph node metastases. Visceral metastases are not allowed. The primary endpoint is radiological progression-free survival (rPFS1), according to PCWG3. Secondary endpoints include: overall survival, PCa specific survival, 1st symptomatic skeletal event (SSE), time to initiation of next systemic anti-neoplastic therapy, time to pain progression, health-related quality of life (EQ-5D-5L and BPI). Clinical trial information: NCT02194842.

Randomised phase III trial of enzalutamide in androgen deprivation therapy (ADT) with radiation therapy for clinically localised, high risk, or node-positive prostate cancer: ENZARAD (ANZUP 1303)

TPS5096

Background: Adjuvant ADT with an LHRH analog (LHRHA) given before, during and after radiotherapy (RT) is standard of care for high risk localised prostate cancer (PC). Enzalutamide is more effective in metastatic disease than conventional non-steroidal anti-androgens (NSAA). We hypothesize that addition of enzalutamide to adjuvant ADT and RT will improve outcomes. The aim is to determine the efficacy of enzalutamide compared with NSAA as part of adjuvant ADT with LHRHA in men planned for RT for localized high risk or node-positive PC. Methods: DESIGN: Open label, randomised, phase 3 trial including ANZ, USA, UK, Ireland and Europe. ENDPOINTS: OS (primary), cause-specific survival, PSA PFS, clinical PFS, time to subsequent hormonal therapy, time to castration-resistant disease (PCWG2 criteria), metastasis free survival, adverse events and HRQOL. Tertiary objectives: identification of prognostic/predictive biomarkers from archival tumour tissue and 4 serial fasting bloods. 800 target participants with 5.5 yrs minimum follow-up. 80% power to detect 33% reduction in the hazard of death assuming 5-year survival rate of 76% amongst controls. TREATMENT: Participants are randomised 1:1 to enzalutamide 160mg daily for 24 months versus conventional NSAA for 6 months. All participants receive LHRHA for 24 months and RT starting after week 16. RT delivered as 78Gy in 39 Fx or 46Gy in 23 Fx plus brachytherapy (nodal RT optional for N0, mandatory for N1). ASSESSMENTS: Baseline, then every 8 weeks until year 2, then 3-4 monthly until year 5, 6-monthly until year 7, then annually. CT/MRI and bone scan at baseline, PSA progression, 6 monthly until re-initiation of ADT, when PCWG2 criteria for CRPC are met and then 3 monthly until evidence of metastases. As of 1st February 2017, 55 of 67 sites open with 398 patients recruited. EORTC sites expected to open from Quarter 1 2017. ENZARAD is an investigator-initiated cooperative group trial led by ANZUP Cancer Trials Group with funds and product from Astellas. ANZUP is supported by Cancer Australia and previously CI NSW. ClinicalTrials.gov: NCT02446444, ANZCTR: ACTRN12614000126617 Clinical trial information: NCT02446444.

Development and validation of a prognostic model for overall survival in chemotherapy-naive men with metastatic castration-resistant prostate cancer (mCRPC) from the phase 3 prevail clinical trial

5022

Background: Prognostic models require updating to reflect contemporary medical practice. In a post hoc analysis of the phase 3 PREVAIL trial (enzalutamide vs placebo), we identified prognostic factors for overall survival (OS) in chemotherapy-naive men with mCRPC. Methods: Patients were randomly divided 2:1 into training (n = 1159) and testing (n = 550) sets. Using the training set, 23 predefined candidate prognostic factors (including treatment) were analyzed in a multivariable Cox model with stepwise procedures and in a penalized Cox proportional hazards model using the adaptive least absolute shrinkage and selection operator (LASSO) penalty (data cutoff June 1, 2014). A multivariable model predicting OS was developed using the training set; the predictive accuracy was assessed in the testing set using time-dependent area under the curve (tAUC). The testing set was stratified based on risk score tertiles (low, intermediate, high), and OS was analyzed using Kaplan-Meier methodology. Results: Demographics, disease characteristics, and OS were balanced between the training and testing sets; median OS was 32.7 months for both datasets. There were no enzalutamide treatment-prognostic factor interactions (predictors). The final multivariable model included 11 prognostic factors: prostate-specific antigen, treatment, hemoglobin, neutrophil-lymphocyte ratio, liver metastases, time from diagnosis to randomization, lactate dehydrogenase, ≥ 10 bone metastases, pain, albumin, and alkaline phosphatase. The tAUC was 0.74 in the testing set. Median (95% confidence interval [CI]) OS for the low-, intermediate-, and high-risk groups (testing set) were not yet reached (NYR) (NYR–NYR), 34.2 months (31.5–NYR), and 21.1 months (17.5–25.0). The hazard ratios (95% CI) for OS in the low- and intermediate-risk groups vs the high-risk group were 0.20 (0.14–0.29) and 0.40 (0.30–0.53), respectively. Conclusions: Our validated prognostic model incorporates factors routinely collected in chemotherapy-naive men with mCRPC treated with enzalutamide and identifies subsets of men with widely differing survival times. Clinical trial information: NCT01212991.

ARASENS phase 3 trial of ODM-201 in men with metastatic hormone-sensitive prostate cancer (mHSPC)

TPS5092

Background: Androgen deprivation therapy (ADT) ± docetaxel is recommended first-line therapy for mHSPC, but most patients progress to castration-resistant PC (CRPC). BAY-1841788 (ODM-201) is an investigational oral androgen receptor (AR) antagonist that has a unique chemical structure designed to block the growth of cancer cells through binding to the AR with high affinity and inhibiting the receptor function. In preclinical studies, ODM-201 and its main circulating metabolite are active also in known AR mutants (eg, W742L, F877L), and have been found to have negligible blood-brain barrier penetration. In the phase 1 ARAFOR and phase 1/2 ARADES trials, ODM-201 had antitumor activity and was well tolerated in men with mCRPC (Massard et al. Eur Urol. 2016;69:834‒840; Fizazi et al. Lancet Oncol. 2014;15:975‒985). Given this promising activity in mCRPC, the ARASENS trial is evaluating ODM-201 plus standard ADT + docetaxel in men with metastatic disease (mHSPC). Methods: This international, randomized, double-blind, placebo-controlled, phase 3 trial (NCT02799602) is being conducted in 23 countries. ~1300 men with newly diagnosed mHSPC will be randomized 1:1 to either ODM-201 600 mg twice daily (2×300 mg tablets) orally with food or placebo, both with ADT + docetaxel (6 cycles after randomization), and stratified by extent of disease and alkaline phosphatase levels. Key inclusion criteria are histologically or cytologically confirmed PC with documented metastases, started ADT ± first-generation anti-androgen therapy ≤12 weeks before randomization, and Eastern Cooperative Oncology Group performance status 0 or 1. The primary objective is to show superior overall survival with ODM-201 vs placebo, both with ADT + docetaxel. Secondary end points include time to CRPC, initiation of subsequent anticancer therapy, symptomatic skeletal event-free survival (SSE-FS), time to first SSE, initiation of opioid use, pain progression, and worsening of physical symptoms, all measured at 12-week intervals. Safety will be assessed by adverse events. The trial is open for enrollment; first patient first visit was in November 2016 and > 10 sites are open for recruitment and enrolling patients. Clinical trial information: NCT02799602.

Prognostic impact of primary tumor location in advanced urothelial carcinoma: The EORTC series

e16034

Background: The prognostic relevance of the primary location of urothelial cell carcinoma (UCC) on outcomes is poorly documented. This parameter has been studied in 3 EORTC trials in advanced UCC that included patients with different initial primary tumor locations. Methods: We used the data prospectively collected in three EORTC advanced UCC studies 30924 (M-VAC versus High dose M-VAC), 30986 (MCAVI versus GC, among patients unfit for CDDP), 30987 (GC-Paclitaxel versus GC, among patients fit for CDDP). Ineligible patients and other tumor locations were excluded. Patients all had measureable distant metastases or unresectable UCC and WHO performance status 0-2. Patients were grouped by primary tumor location as bladder (BCa) versus upper urinary tract (UTUC). PFS and OS by tumor location was tested in Cox proportional hazard regression stratified by study and treatment using at 2-sided α of 0.05. Results: Of the 1,039 patients, 85.3% and 14.7% patients had BCa and UTUC, respectively. Patient and disease characteristics (Table) suggested better performance status and slightly more males among patients with GCa. With a median follow up of 4.8 years (IQR:4.0-6.7), 733 deaths were recorded and 925 had progressed or died. OS and PFS did not differ significantly by tumor location overall (P=0.317 and P=0.685 respectively, Table 1), but there is significant heterogeneity across treatments (heterogeneity P=0.0450 for OS and P=0.0121 for PFS) with a suggestion of differential results in the M-CAVI arm for unfit patients. Conclusions: Primary UTUC location is uncommon in advanced UCC and did not seem to markedly impact PFS or OS. However, the findings may vary according to treatment. [Table: see text]

Patient (pt) characteristics and treatment patterns in the radium (Ra)-223 REASSURE observational study

5042

Background: Ra-223, a targeted alpha therapy, prolonged survival with good safety in metastatic castration-resistant prostate cancer (mCRPC) in the phase 3 ALSYMPCA trial. REASSURE will evaluate Ra-223 short- and long-term safety in routine clinical practice settings. This is the first planned interim analysis (median 7 mo observation). Methods: This global, prospective, single-arm, observational study enrolled pts with mCRPC with bone metastases (mets) for whom Ra-223 therapy was planned. Follow-up will continue up to 7 years after last Ra-223 dose. Results: 1106 pts (437 N. America, 665 Europe, 4 not recorded) enrolled from 2 Sep 2014 to 22 Sep 2016. Baseline data are available from 583 pts receiving 1st- (1L), 2nd- (2L), or ≥3rd-line (≥3L) Ra-223 for mCRPC(Table). The majority of pts (n=369, 63%) completed 5–6 doses (1L, 70%; 2L, 64%; ≥3L, 49%); median 6 doses (1L,6; 2L, 6; ≥3L, 4). Treatment-emergent drug-related AEs occurred in 215 pts (37%). Post-treatment grade 3/4 thrombocytopenia occurred in 14 pts (2.4%) and anemia in 45 (7.7%). Conclusions: In routine clinical practice, Ra-223 was associated with no short-term safety concerns and appeared to be used in pts with less advanced mCRPC than in ALSYMPCA. The majority of pts on 1L/2L Ra-223 therapy received 5–6 doses. Ra-223 was often used with abiraterone or enzalutamide, but not chemotherapy. The next interim analysis in 2019 will report long-term safety and outcomes on all pts. Clinical trial information: NCT02141438. [Table: see text]

Development and validation of a prognostic model for overall survival in chemotherapy-naïve men with metastatic castration-resistant prostate cancer (mCRPC) from the phase III PREVAIL clinical trial

138

Background: Prognostic models require updating to reflect contemporary medical practice. In a post hoc analysis of the phase 3 PREVAIL trial (enzalutamide vs placebo), we identified prognostic factors for overall survival (OS) in chemotherapy-naïve men with mCRPC. Methods: Patients were randomly divided 2:1 into training (n = 1159) and testing (n = 550) sets. Using the training set, 23 predefined candidate prognostic factors (including treatment) were analyzed in a multivariable Cox model with stepwise procedures and in a penalized Cox proportional hazards model using the adaptive least absolute shrinkage and selection operator (LASSO) penalty (data cutoff June 1, 2014). A multivariable model predicting OS was developed using the training set; the predictive accuracy was assessed in the testing set using time-dependent area under the curve (tAUC). The testing set was stratified based on risk score tertiles (low, intermediate, high), and OS was analyzed using Kaplan-Meier methodology. Results: Demographics, disease characteristics, and OS were balanced between the training and testing sets; median OS was 32.7 months for both datasets. There were no enzalutamide treatment-prognostic factor interactions (predictors). The final multivariable model included 11 prognostic factors: prostate-specific antigen, treatment, hemoglobin, neutrophil-lymphocyte ratio, liver metastases, time from diagnosis to randomization, lactate dehydrogenase, ≥ 10 bone metastases, pain, albumin, and alkaline phosphatase. The tAUC was 0.74 in the testing set. Median (95% confidence interval [CI]) OS for the low-, intermediate-, and high-risk groups (testing set) were not yet reached (NYR) (NYR–NYR), 34.2 months (31.5–NYR), and 21.1 months (17.5–25.0). The hazard ratios (95% CI) for OS in the low- and intermediate-risk groups vs the high-risk group were 0.20 (0.14–0.29) and 0.40 (0.30–0.53), respectively. Conclusions: Our validated prognostic model incorporates factors routinely collected in chemotherapy-naïve men with mCRPC treated with enzalutamide and identifies subsets of men with widely differing survival times.

Long-term efficacy and safety of enzalutamide (ENZ) monotherapy in hormone-naïve prostate cancer (HNPC): 3-year, open-label, follow-up results

220

Background: A phase 2 study of the androgen receptor inhibitor ENZ as monotherapy in patients with HNPC [NCT01302041] showed a high prostate-specific antigen (PSA) response rate, regardless of baseline metastases, and favorable tolerability. In a 1- and 2-year follow-up, ENZ maintained long-term reductions from baseline in PSA, with minimal impact on total-body bone mineral density (BMD). Herein, results from a pre-specified 3-year follow-up are reported. Methods: A total of67 patients with HNPC and non-castrate testosterone ( ≥ 230 ng/dL) received ENZ 160 mg/day until disease progression or unacceptable toxicity. The primary end point of PSA response ( ≥ 80% decline from baseline) was analyzed at week 25 and 1, 2, and 3 years. Other end points were best overall tumor response, BMD, body composition, quality of life, and safety. Results: At the 3-year visit, 42 (62.7%) patients remained on the study medication. Of those, 38 (90.5%; 95% confidence interval 77.4%, 97.3%) maintained a PSA response. Of the 26 patients with metastases at baseline, 17 (65.4%) had a complete or partial response as best overall response at 3 years. In patients who completed the 3-year visit, minimal changes from baseline were observed in total-body BMD or in BMD of the femoral neck, trochanter, spine L1–L4, or forearm (median and mean changes ranged from –3.6% to 1.3% and –2.7% to –0.1%, respectively). The EORTC QLQ-C30 global health status results showed a small decrease at 3 years versus baseline (–3.96 points), consistent with the 2-year results. At 3 years, measurements for total body fat increased (median, 14.7%; mean, 16.5%) and total body lean decreased (median, –6.3%; mean, –6.5%) from baseline. Physical functioning, fatigue, and dyspnea worsened ( > 10 points) at 3 years, similar to results at 2 years. The most frequently reported adverse events ( > 10%) were gynecomastia, fatigue, hot flush, nipple pain, hypertension, diarrhea, nausea, pain in extremity, back pain, and constipation. Conclusions: In patients with HNPC treated with ENZ for 3 years, the efficacy of ENZ as monotherapy was maintained. Overall, BMD, global health status, and safety results were similar to those at 2 years. Clinical trial information: NCT01302041.

A randomized trial of abiraterone acetate (AA) administered with 1 of 4 glucocorticoid (GC) regimens in metastatic castration-resistant prostate cancer (mCRPC) patients (pts)

261

Background: AA is approved for mCRPC, coadministered with prednisone (P) (5 mg BID) to prevent adverse events (AEs) associated with mineralocorticoid excess (ME). Lower GC doses had not previously been formally evaluated in combination with AA. Methods: This was an open-label, multicenter, phase 2 trial (NCT01867710) of asymptomatic chemotherapy-naïve mCRPC pts randomized 1:1:1:1 to AA (1000 mg QD) plus P 5 mg BID or P 5 mg QD or P 2.5 mg BID or dexamethasone (DEX) 0.5 mg QD. Pts who had previously received GC or ketoconazole were excluded. The primary end point was no ME (% of pts experiencing neither hypokalemia nor hypertension during the first 24 weeks of treatment).Secondary end points included additional safety, as well as response rate in the first 24 weeks, defined as a decline in prostate-specific antigen (PSA) ≥ 50% confirmed after 4 weeks. Results: 164 pts were randomized; 133 (81.6%) completed 24 weeks’ treatment. Median age: 70 years. Table 1 shows the rates of ME, hypertension, hypokalemia and PSA response. Changes in HbA1c values were minimal and observed in 16 (10.7%) pts. Conclusions: These data suggest that P 5 mg BID, which is approved in combination with AA, and DEX 0.5 mg QD, are effective in preventing ME-associated AEs, and that P 2.5 mg BID and P 5 mg QD can be safely used with appropriate monitoring. The suggestion of a higher PSA response rate with DEX 0.5 mg QD arm warrants further validation. Clinical trial information: NCT01867710. [Table: see text]

Correlation between radiographic progression-free survival (rPFS) and overall survival (OS): Results from PREVAIL

182

Background: In PREVAIL, enzalutamide (ENZA) significantly improved OS (hazard ratio [HR] 0.71; P < 0.0001) and rPFS (HR 0.19; P < 0.0001) compared with placebo in chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). Using data from the final analysis at 439 rPFS events we showed a strong correlation between investigator and central review. Here we report sensitivity analyses (SAs) from the final analysis of investigator-assessed rPFS and the association between investigator-assessed rPFS and OS. Methods: The coprimary endpoint of rPFS was defined as time from randomization to the earliest objective evidence of centrally assessed radiographic progression, defined by PCWG2 guidelines for bone disease and RECIST v1.1 for soft-tissue disease, or death within 168 days of treatment discontinuation. Bone progression was captured using a validated bone scan data capture assay. Four SAs were performed on investigator-assessed rPFS to evaluate the impact of: (1) progression in bone, (2) clinical progression, (3) a required confirmatory scan for soft-tissue disease progression, and (4) all deaths, regardless of length of time after study drug discontinuation. Associations of investigator-assessed rPFS and OS were calculated using Pearson’s correlation coefficient, Spearman’s rho, and Spearman’s rho estimated through the Clayton copula. Results: Treatment effects remained significant with each SA, with HRs of (1) 0.21 (95% confidence interval [CI] 0.18, 0.27), (2) 0.21 (95% CI 0.17, 0.26), (3) 0.23 (95% CI 0.19, 0.30), and (4) 0.23 (95% CI 0.19, 0.30) (P < 0.0001 for each). Results of rPFS and OS associations are presented in the table below. Conclusions: SAs of rPFS in PREVAIL demonstrated a robust and consistent treatment benefit with ENZA. We observed a modest association between rPFS and OS. However, some unaccounted factors, such as post-protocol treatment, could have reduced the strength of the association of rPFS and OS in the placebo arm. Clinical trial information: NCT01212991. [Table: see text]

Association of changes in measurable disease by RECIST with survival in metastatic castration-resistant prostate cancer (mCRPC)

186

Background: In men with mCRPC receiving chemotherapy, measurable disease response by World Health Organization criteria has been demonstrated to be prognostic for overall survival (OS). We aimed to explore the association of changes in measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) with OS. Methods: Data from the control arm (n=612) of the phase III VENICE trial receiving docetaxel plus prednisone combined with placebo were available. Data on baseline clinical and laboratory variables were obtained in addition to outcome measures: best RECIST 1.0 response, PSA response and OS. Cox proportional hazards regression was used to evaluate the prognostic ability of RECIST-defined changes for OS using a 90-day landmark analysis. Results: 363 of 612 patients (59.3%) had measurable lesions, of whom 296 were evaluable for landmark analysis. 28 (9.5%) had progressive disease (PD) prior to day 90, while 58 (19.6%) had unconfirmed partial response (PR), i.e. declines ≥30% of the sum of diameters of target lesions. Median OS beyond day 90 for men with PR, stable disease (SD), and PD was 28.3, 23.3, 11.4 months, respectively (P < 0.001). In a multivariable analysis adjusting for pain, PCWG-2 subtype, type of progression (PSA vs. other), Gleason Score (≤ 7 vs. > 7), PSA, derived neutrophil-lymphocyte ratio, ECOG performance status and alkaline phosphatase, the hazard ratio (HR) for OS for patients with PR was 0.64 (95% CI 0.42 – 0.99, P = 0.045) compared to those without PR, and 1.78 (95% CI 1.07 – 2.95, P = 0.026) for those with PD compared to those without PD. PD remained significant (HR = 1.85, 95% CI 1.10 – 3.12, P = 0.020) after adjusting for PSA changes, but PR (P = 0.14) did not. Conclusions: In men with mCRPC receiving first-line docetaxel-based chemotherapy PR and PD by RECIST 1.0 within 90 days were associated with longer or shorter OS, respectively. Given the more frequent detection of measurable disease with current imaging, the accrual of patients with measurable tumors in phase II trials to assess RECIST changes may provide an objective signal of efficacy of new drugs.

Charlson score to predict overall survival and cancer-related death in elderly patients featuring high-risk prostate cancer

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Background: In elderly patients, Charlson score among other features, might allow clinicians to limit the use of aggressive adjuvant treatment strategies or even primary surgical treatment to those who might not achieve benefit during their lifetime. Methods: Retrospective analysis, 7,650 case multicenter high-risk prostate cancer (Pca) radical prostatectomy database selecting >= 70 years old cases. We predicted death from all causes (DAC) and cancer related death (CRD) including all clinical and pathological data. Multivariable analysis were performed to identify independent predictors of DAC and CRD with binary logistic regression, using STATA® software, version 13.1. Results: 2,106 patients from 14 high-volume centers were included. Mean age was 72.8 years (SD 2.46). 206 (9.78%) patients were classified as ASA 3-4 and 497 (23.6%) as CS >=1. Mean PSA was 21.7 ng/ml (SD 50.5). At final histopathology, 800 (38%) had pT3b-T4 disease, GS was 8-10 in 589 (28%), LNI was found in 518 (24.6%) and 822 (39%) PSM. Adjuvant RT, ADT and RT+ADT were administered in 359 (17%), 391 (18.6%) and 437 (20.7%), respectively. Mean follow up was 5.18 years (DS 4.47). BCR occur in 649 (30.8%) and CF in 150 (7.1%) of which distant in 59 (2.8%). Total deaths accounted 341 (16.2%) and CRD for 100 (4.7%) cases. Conclusions: Multicenter data confirms that elderly patients survival harboring high risk prostate cancer will benefit from radical treatment if they are Charlson score 1 or less. [Table: see text] [Table: see text]

Subgroup analyses of Japanese patients from the PREVAIL trial of enzalutamide (ENZA) in patients with chemotherapy-naïve, metastatic castration-resistant prostate cancer (mCRPC)

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Background: In PREVAIL, an international phase 3 randomized trial, treatment with ENZA decreased the risk of radiographic progression or death by 81% and the risk of death by 29% compared with placebo. We evaluated efficacy, safety and pharmacokinetic exposure with ENZA in the Japanese subgroup of patients participating in PREVAIL. Methods: Asymptomatic or mildly symptomatic chemotherapy-naïve patients with mCRPC progressing on androgen deprivation therapies were randomized 1:1 to ENZA 160 mg or placebo until discontinuation upon radiographic progression or initiation of chemotherapy. Continued androgen-deprivation therapy was required. Coprimary endpoints were overall survival (OS) and radiographic progression-free survival (rPFS). Prostate-specific antigen (PSA) response was defined as a confirmed ≥50% reduction from baseline to nadir. Results: A total of 1,717 patients (ENZA: 872, placebo: 845) were randomized in PREVAIL, of which 61 patients were Japanese (ENZA: 28, placebo: 33). The trial was halted after a planned interim analysis at which hazard ratios calculated for OS (0.71; 95%CI: 0.60-0.84) and rPFS (0.19; 95%CI: 0.15-0.23) showed significant benefit of ENZA vs placebo. Hazard ratios for OS and rPFS in Japanese patients were 0.60 (95%CI: 0.20-1.78) and 0.29 (95%CI: 0.030-2.95), respectively. Time to chemotherapy was delayed from a median 10 months on placebo vs not yet reached on ENZA, with a hazard ratio of 0.46 (95%CI: 0.22-0.96). PSA responses were more common in Japanese patients receiving ENZA (61%) vs placebo (21%) (treatment effect = 39.5%; 95%CI: 16.7%-62.3%). Plasma concentration of ENZA was slightly higher in the Japanese subgroup: geometric mean Cmin= 13.8 µg/mL vs 12.3 µg/mL in the non-Japanese cohort at 13 weeks. In the Japanese subgroup adverse events (AEs) ≥ Grade 3 were reported by 9/28 patients (32%) on ENZA vs 13/33 patients (39%) on placebo. Treatment-related AEs ≥ Grade 3 were rare: in the ENZA arm (1/28; 3.6%) and in the placebo arm (2/33; 6.1%). Conclusions: Theefficacy and safety results in the Japanese subgroup were generally consistent with the overall results from the PREVAIL trial. Clinical trial information: NCT01212991.

Clinical outcomes and safety in men ≥ 75 and < 75 years with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide in the phase 3 PREVAIL trial

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Background: In the phase 3 PREVAIL trial, enzalutamide (ENZA), an androgen receptor inhibitor, improved overall survival (OS) and radiographic progression-free survival (rPFS) relative to placebo (PBO) in chemotherapy-naïve men with mCRPC. Methods: PREVAIL randomized 1,717 patients (pts) with asymptomatic or minimally symptomatic chemotherapy-naïve mCRPC 1:1 to ENZA 160 mg daily or PBO. Coprimary endpoints were OS and rPFS. This prespecified analysis evaluated the impact of age (≥ 75 vs < 75 years) on efficacy and safety. Results: In PREVAIL, 609 (35%) pts were aged ≥ 75 years. This older subset had several poorer baseline prognostics relative to those aged < 75 years: worse ECOG performance status (ECOG 1: 45.0% vs 24.7%), higher prostate-specific antigen (PSA; 73.3 vs 37.3 ng/mL) and more cardiovascular disease (26.9% vs 16.5%). In both older and younger pts, ENZA improved OS, rPFS and time to PSA progression (Table). Pts aged ≥ 75 years in both the ENZA and PBO groups combined had a higher rate of grade ≥ 3 adverse events (46% vs 37% in younger pts) and among enzalutamide-treated men more older pts reported falls (any grade; ENZA 19% and PBO 8%) than younger pts (ENZA 7% and PBO 4%). Fewer pts ≥ 75 years received subsequent antineoplastic therapies. Conclusions: In PREVAIL, efficacy outcomes in elderly (≥ 75 years) and younger (< 75 years) pts with chemotherapy-naïve mCRPC were comparable and pts consistently benefited from ENZA treatment. Safety with ENZA was similar in both age groups, although older pts reported a higher incidence of falls and received fewer subsequent antineoplastic therapies. Clinical trial information: NCT01212991. [Table: see text]