Development and validation of a prognostic model for overall survival in chemotherapy-naïve men with metastatic castration-resistant prostate cancer

BackgroundPrognostic models are needed that reflect contemporary practice for men with metastatic castration-resistant prostate cancer (mCRPC). We sought to identify predictive and prognostic variables for overall survival (OS) in chemotherapy-naïve men with mCRPC treated with enzalutamide.Patients and methodsPatients from the PREVAIL trial database (enzalutamide versus placebo) were randomly split 2 : 1 into training (n = 1159) and testing (n = 550) sets. Using the training set, 23 predefined variables were analyzed and a multivariable model predicting OS was developed and validated in an independent testing set.ResultsPatient characteristics and outcomes were well balanced between training and testing sets; median OS was 32.7 months in each. The final validated multivariable model included 11 independent prognostic variables. Median OS for low-, intermediate-, and high-risk groups (testing set) defined by prognostic risk tertiles were not yet reached (NYR) (95% CI NYR–NYR), 34.2 months (31.5–NYR), and 21.1 months (17.5–25.0), respectively. Hazard ratios (95% CI) for OS in the low- and intermediate-risk groups versus high-risk group were 0.20 (0.14–0.29) and 0.40 (0.30–0.53), respectively. Secondary outcomes of response and progression differed widely in model-defined risk groups. Enzalutamide improved outcomes in all prognostic risk groups.ConclusionsOur validated prognostic model incorporates variables routinely collected in chemotherapy-naïve men with mCRPC treated with enzalutamide, identifying subsets of patients with widely differing survival outcomes that provide useful information for external validation, patient care, and clinical trial design.Trial registrationClinicalTrials.gov: NCT01212991.     

Long-term use and risk of major adverse cardiac events: Comparing enzalutamide and abiraterone in chemotherapy-naïve patients with metastatic castration-resistant prostate cancer

This is a retrospective cohort study by analyzing a multi-institutional electronic medical records database in Taiwan to compare long-term effectiveness and risk of major adverse cardiac events (MACE) in chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC) patients treated with enzalutamide (ENZ) or abiraterone (AA). Patients aged 20 years and older and newly receiving androgen receptor targeted therapies ENZ or AA from September 2016 to December 2019 were included. We followed patients from initiation of therapies to the occurrence of outcomes (prostate-specific antigen (PSA) response rate, PSA progression free survival (PFS), overall survival (OS), and MACE), death, the last clinical visit, or December 31, 2020. We performed multivariable Cox proportional hazard models to compare ENZ and AA groups for the measured outcomes. A total of 363 patients treated with either ENZ (n = 157) or AA (n = 206) were identified. The analysis found a significantly higher proportion of patients with a PSA response rate higher than 50% among those receiving ENZ than among those receiving AA (ENZ vs AA: 75.80% vs 63.59%, P = .01). However, there was no significant difference in PSA PFS (adjusted hazard ratio: 0.86; 95% CI 0.63-1.17) and OS (0.68: 0.41-1.14) between the use of ENZ and AA in chemotherapy-naïve mCRPC patients. Regarding the cardiovascular (CV) safety outcome, there was a significantly lower risk of MACE in patients receiving ENZ, compared to patients receiving AA (0.20: 0.07-0.55). The findings suggest that enzalutamide may be more efficacious for PSA response and suitable for chemotherapy-naïve mCRPC patients with high CV risk profile.     

Treatment of mCRPC in the AR-axis-targeted therapy-resistant state

BackgroundThe increased use of the androgen receptor axis-targeted (ARAT) agents abiraterone and enzalutamide in first- and second-line treatment of metastatic castration-resistant prostate cancer (mCRPC) has improved patient outcomes, but resistance to these agents is inevitable. Early identification of patients with primary or secondary resistance to ARAT therapy is of increasing clinical concern.DesignPubMed and conference proceedings were searched for studies of agents used after progression on abiraterone or enzalutamide. The key search terms (or aliases) used a combination of mCRPC and abiraterone or enzalutamide, and results were limited to clinical trials and comparative or validation studies.Results and conclusionThis systematic review assembles current evidence and provides an approach to treatment using available clinical factors. Issues of patient selection, use of laboratory and clinical biomarkers to identify patients at risk of poor outcomes, and the timing and sequencing of available treatment options are addressed. Our findings reveal a lack of high-level evidence regarding predictive factors and treatment of patients with resistance to ARAT therapy, and a need for further research in this area. In the meantime, we suggest practical strategies to guide management of ARAT treatment-resistant patients based on available data.     

Does Gleason score at initial diagnosis predict efficacy of abiraterone acetate therapy in patients with metastatic castration-resistant prostate cancer? An analysis of abiraterone acetate phase III trials

BackgroundThe usefulness of Gleason score (<8 or ≥8) at initial diagnosis as a predictive marker of response to abiraterone acetate (AA) plus prednisone in patients with metastatic castration-resistant prostate cancer (mCRPC) was explored retrospectively.Patients and methodsInitial diagnosis Gleason score was obtained in 1048 of 1195 (COU-AA-301, post-docetaxel) and 996 of 1088 (COU-AA-302, chemotherapy-naïve) patients treated with AA 1 g plus prednisone 5 mg twice daily by mouth or placebo plus prednisone. Efficacy end points included radiographic progression-free survival (rPFS) and overall survival (OS). Distributions and medians were estimated by Kaplan–Meier method and hazard ratio (HR) and 95% confidence interval (CI) by Cox model.ResultsBaseline characteristics were similar across studies and treatment groups. Regardless of Gleason score, AA treatment significantly improved rPFS in post-docetaxel [Gleason score <8: median, 6.4 versus 5.5 months (HR = 0.70; 95% CI 0.56–0.86), P = 0.0009 and Gleason score ≥8: median, 5.6 versus 2.9 months (HR = 0.58; 95% CI 0.48–0.72), P < 0.0001] and chemotherapy-naïve patients [Gleason score <8: median, 16.5 versus 8.2 months (HR = 0.50; 95% CI 0.40–0.62), P < 0.0001 and Gleason score ≥8: median, 13.8 versus 8.2 months (HR = 0.61; 95% CI 0.49–0.76), P < 0.0001]. Clinical benefit of AA treatment was also observed for OS, prostate-specific antigen (PSA) response, objective response and time to PSA progression across studies and Gleason score subgroups.ConclusionOS and rPFS trends demonstrate AA treatment benefit in patients with pre- or post-chemotherapy mCRPC regardless of Gleason score at initial diagnosis. The initial diagnostic Gleason score in patients with mCRPC should not be considered in the decision to treat with AA, as tumour metastases may no longer reflect the histology at the time of diagnosis.Clinical trials numberCOU-AA-301 (NCT00638690); COU-AA-302 (NCT00887198).     

Androgen receptor gene status in plasma DNA associates with worse outcome on enzalutamide or abiraterone for castration-resistant prostate cancer: a multi-institution correlative biomarker study

BackgroundThere is an urgent need to identify biomarkers to guide personalized therapy in castration-resistant prostate cancer (CRPC). We aimed to clinically qualify androgen receptor (AR) gene status measurement in plasma DNA using multiplex droplet digital PCR (ddPCR) in pre- and post-chemotherapy CRPC.MethodsWe optimized ddPCR assays for AR copy number and mutations and retrospectively analyzed plasma DNA from patients recruited to one of the three biomarker protocols with prospectively collected clinical data. We evaluated associations between plasma AR and overall survival (OS) and progression-free survival (PFS) in 73 chemotherapy-naïve and 98 post-docetaxel CRPC patients treated with enzalutamide or abiraterone (Primary cohort) and 94 chemotherapy-naïve patients treated with enzalutamide (Secondary cohort; PREMIERE trial).ResultsIn the primary cohort, AR gain was observed in 10 (14%) chemotherapy-naïve and 33 (34%) post-docetaxel patients and associated with worse OS [hazard ratio (HR), 3.98; 95% CI 1.74–9.10; P < 0.001 and HR 3.81; 95% CI 2.28–6.37; P < 0.001, respectively], PFS (HR 2.18; 95% CI 1.08–4.39; P = 0.03, and HR 1.95; 95% CI 1.23–3.11; P = 0.01, respectively) and rate of PSA decline ≥50% [odds ratio (OR), 4.7; 95% CI 1.17–19.17; P = 0.035 and OR, 5.0; 95% CI 1.70–14.91; P = 0.003, respectively]. AR mutations [2105T>A (p.L702H) and 2632A>G (p.T878A)] were observed in eight (11%) post-docetaxel but no chemotherapy-naïve abiraterone-treated patients and were also associated with worse OS (HR 3.26; 95% CI 1.47–not reached; P = 0.004). There was no interaction between AR and docetaxel status (P = 0.83 for OS, P = 0.99 for PFS). In the PREMIERE trial, 11 patients (12%) with AR gain had worse PSA-PFS (sPFS) (HR 4.33; 95% CI 1.94–9.68; P < 0.001), radiographic-PFS (rPFS) (HR 8.06; 95% CI 3.26–19.93; P < 0.001) and OS (HR 11.08; 95% CI 2.16–56.95; P = 0.004). Plasma AR was an independent predictor of outcome on multivariable analyses in both cohorts.ConclusionPlasma AR status assessment using ddPCR identifies CRPC with worse outcome to enzalutamide or abiraterone. Prospective evaluation of treatment decisions based on plasma AR is now required.Clinical Trial numberNCT02288936 (PREMIERE trial).     

Treatment Patterns and Outcomes in Patients With Metastatic Castration-resistant Prostate Cancer in a Real-world Clinical Practice Setting in the United States

BackgroundClinical trials have demonstrated the efficacy of several life-prolonging therapies for metastatic castration-resistant prostate cancer (mCRPC); however, real-world data on their use, survival effect, and safety are limited. Using electronic health record data from the Flatiron Health database, we studied real-world treatment patterns and health outcomes in patients with mCRPC.Patients and MethodsWe conducted a retrospective, non-interventional cohort analysis of electronic health record data of patients with confirmed mCRPC between January 2013 and September 2017. The primary objective was to describe real-world treatment patterns, including treatment type, duration, and sequencing. Secondary objectives included describing patient characteristics and clinical outcomes.ResultsOf 2559 patients with mCRPC, 1980 (77%) received at least 1 line of life-prolonging therapy (abiraterone, enzalutamide, docetaxel, cabazitaxel, sipuleucel-T, or radium-223). Of patients receiving first-line therapy, 49% received second-line therapy, and of these, 43% received third-line therapy. Abiraterone/prednisone and enzalutamide accounted for 65% of first-line therapies and 54% of second-line therapies. Docetaxel was the most common third-line therapy (24%). Back-to-back use of abiraterone/prednisone and enzalutamide was common. Radium-223 monotherapy use was 2% in the first-line setting, 3% in the second-line setting, and 8% in the third-line setting. The median overall survival was longer in patients who received life-prolonging therapies (23.7 months; 95% confidence interval: 22.3-25.1 months) than in those who did not (10.1 months; 95% confidence interval: 9.1-11.5 months).ConclusionThese real-world insights on over 2500 patients with mCRPC supplement findings from randomized controlled trials and may help to inform clinical trial design, treatment guidelines, and clinical decision-making.     

Adjusting Overall Survival Estimates after Treatment Switching: a Case Study in Metastatic Castration-Resistant Prostate Cancer

Background

If patients in oncology trials receive subsequent therapy, standard intention-to-treat (ITT) analyses may inaccurately estimate the overall survival (OS) effect of the investigational product. In this context, a post-hoc analysis of the phase 3 PREVAIL study was performed with the aim to compare enzalutamide with placebo in terms of OS, adjusting for potential confounding from switching to antineoplastic therapies that are not part of standard metastatic castration-resistant prostate cancer (mCRPC) treatment pathways in some jurisdictions.

Methods

The PREVAIL study, which included 1717 chemotherapy-naïve men with mCRPC randomized to treatment with enzalutamide 160 mg/day or placebo, was stopped after a planned interim survival analysis revealed a benefit in favor of enzalutamide. Data from this cutoff point were confounded by switching from both arms and so were evaluated in terms of OS using two switching adjustment methods: the two-stage accelerated failure time model (two-stage method) and inverse probability of censoring weights (IPCW).

Results

Following adjustment for switching to nonstandard antineoplastic therapies by 14.8 (129/872 patients) and 21.3% (180/845 patients) of patients initially randomized to enzalutamide and placebo, respectively, the two-stage and IPCW methods both resulted in numerical reductions in the hazard ratio (HR) for OS [HR 0.66, 95% confidence interval (CI) 0.57–0.81 and HR 0.63, 95% CI 0.52–0.75, respectively] for enzalutamide compared to placebo versus the unadjusted ITT analysis (HR 0.71, 95% CI 0.60–0.84). These results suggest a slightly greater effect of enzalutamide on OS than originally reported.

Conclusion

In the PREVAIL study, switching to nonstandard antineoplastic mCRPC therapies resulted in the ITT analysis of primary data underestimating the benefit of enzalutamide on OS.

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Cross-resistance between taxanes and new hormonal agents abiraterone and enzalutamide may affect drug sequence choices in metastatic castration-resistant prostate cancer

IntroductionTreatment options for patients with metastatic castration-resistant prostate cancer (mCRPC) have expanded in recent years with the introduction of cabazitaxel, abiraterone and enzalutamide. With new systemic therapies available, the optimal treatment sequence of these drugs in mCRPC becomes increasingly important. As shown recently, patients who had previously been treated with abiraterone showed impaired responses to docetaxel, suggesting clinical cross-resistance [1]. In the present study, we aimed to identify cross-resistance between taxanes (docetaxel and cabazitaxel) and the new hormonal agents abiraterone and enzalutamide. As a potential mechanism for cross-resistance, we investigated the effects on androgen receptor (AR) nuclear translocation of these compounds.MethodsTo identify cross-resistance, we determined the effects of docetaxel, cabazitaxel, abiraterone and enzalutamide on cell viability in prostate cancer cell lines with acquired resistance to abiraterone and enzalutamide. Time-lapse confocal microscopy was used to study the dynamics of AR nuclear translocation.ResultsWe observed impaired efficacy of docetaxel, cabazitaxel and enzalutamide in the abiraterone-resistant cell line, compared to the non-resistant cell line, providing evidence for in vitro cross-resistance. Impaired efficacy of docetaxel, cabazitaxel and abiraterone was observed in the enzalutamide-resistant cell line. Furthermore, docetaxel and cabazitaxel inhibited AR nuclear translocation, which was also observed for abiraterone and enzalutamide.ConclusionsIn conclusion we found substantial preclinical evidence for cross-resistance between the taxanes docetaxel and cabazitaxel, and AR targeting agents abiraterone and enzalutamide. Since these compounds all interfere with AR-signalling, this strongly suggests a common mechanism of action, and thus a potential mechanism for cross-resistance in mCRPC.     

Current therapeutic options in metastatic castration-resistant prostate cancer

Background

The tumors of many patients with prostate cancer eventually become refractory to androgen deprivation therapy with progression to metastatic castration-resistant disease. Significant advances in the treatment of metastatic castration-resistant prostate cancer (mCRPC) have been made in recent years, and new treatment strategies have recently been made available. The aim of this report was to schematically review all the approved pharmacologic treatment options for patients with mCRPC through 2018, analyzing the efficacy and possible side effects of each therapy to assist clinicians in reaching an appropriate treatment decision. New biomarkers potentially of aid in the choice of treatment in this setting are also briefly reviewed.

Systemic Therapy in Men with Metastatic Castration-resistant Prostate Cancer: A Systematic Review

AimsSince 2004, docetaxel-based chemotherapy has been the standard of care for men with metastatic castration-resistant prostate cancer (mCRPC), but recently randomised controlled trials (RCTs) of novel agents have shown promise in extending overall survival. These trials have evaluated agents delivered before chemotherapy, to replace or supplement docetaxel, or addressed treatment options for men who have progressed on docetaxel therapy. This review was undertaken to determine which systemic therapies improve cancer- or patient-related outcomes in men with mCRPC.Materials and methodsSearches were carried out in MEDLINE, EMBASE, the Cochrane Library and relevant conference proceedings. Eligible articles included RCTs comparing systemic therapy or combination (excluding primary or secondary androgen deprivation therapy, bone protective agents or radionuclides) with placebo or other agents in men with mCRPC.ResultsTwenty-five RCTs met the selection criteria. In chemotherapy-naive patients, targeted therapy with tasquinimod conferred a benefit in progression-free survival. Immunotherapy with sipuleucel-T extended overall survival and was well tolerated, but had no effect on the time to disease progression. Hypercastration with abiraterone extended progression-free survival, whereas overall survival was improved but not statistically proven. In the chemotherapy setting, updated and new trials of docetaxel alone confirmed the survival benefit seen in previous studies. A survival benefit with the addition of estramustine to docetaxel shown in a previous study did not lead to an improvement in pain palliation or quality of life. Trials of combining targeted therapies with docetaxel generally did not extend survival. The addition of bevacizumab improved progression-free survival, but not overall survival. The addition of GVAX immunotherapy or calcitriol was harmful. In the post-chemotherapy setting, progression-free and overall survival benefits were detected with cabazitaxel, abiraterone and enzalutamide. Cabazitaxel was associated with greater toxicity, whereas abiraterone and enzalutamide had less severe adverse effects. Satraplatin and sunitinib both extended progression-free survival, but did not improve overall survival.ConclusionDocetaxel-based chemotherapy remains the standard of care in men with mCRPC who are candidates for palliative systemic therapy. Promising results are emerging with sipuleucel-T and abiraterone in the pre-docetaxel setting and cabazitaxel, abiraterone and enzalutamide in patients who progress on or after docetaxel. Further research to determine the optimal choice, sequence or even the combination of these agents is necessary.     

Antitumour activity of abiraterone acetate against metastatic castration-resistant prostate cancer progressing after docetaxel and enzalutamide (MDV3100)

BackgroundAndrogen receptor (AR) signalling remains critically important in metastatic castration-resistant prostate cancer (mCRPC) as confirmed by recent phase III trials, showing a survival advantage for abiraterone acetate and enzalutamide (MDV3100). The antitumour activity of abiraterone and prednisolone in patients pre-treated with enzalutamide is as yet unknown.Patients and methodsWe investigated the antitumour activity of abiraterone and prednisolone in patients with mCRPC who had progressed following treatment with docetaxel (Taxotere) and enzalutamide. Clinical data were retrospectively analysed for prostate-specific antigen (PSA) and RECIST responses, clinical benefit and survival.ResultsThirty-eight patients were included in the analysis. The median age was 71 years (range 52–84); metastatic sites included bone disease in 37 patients (97%), lymph nodes in 15 patients (39%) and visceral disease in 10 patients (26%). Abiraterone was well tolerated. Three patients (8%) attained a PSA response, defined as ≥50% decline in PSA confirmed after ≥4 weeks, while seven patients (18%) had a ≥30% PSA decline. The median progression-free survival (PFS) was 2.7 months (95% CI 2.3–4.1). Of the 12 patients assessable radiologically, only 1 (8%) attained a confirmed partial response.ConclusionAbiraterone and prednisolone have modest antitumour activities in patients with mCRPC pretreated with docetaxel and enzalutamide.     

A Single-arm Phase II Study Combining NLG207, a Nanoparticle Camptothecin,with Enzalutamide in Advanced Metastatic Castration-resistant Prostate Cancer Post-Enzalutamide

BackgroundDespite the clinical efficacy of enzalutamide monotherapy in patients with advanced prostate cancer, therapeutic resistance and disease progression are inevitable. We proposed a study to evaluate NLG207, a nanoparticle-drug conjugate (NDC) of the potent topoisomerase I inhibitor camptothecin, in combination with enzalutamide, in patients with metastatic castration-resistant prostate cancer (mCRPC) following progression on enzalutamide.MethodsThis was a single-arm, optimal two-stage, phase II study to evaluate the efficacy of NLG207 in combination with enzalutamide in patients with mCRPC who received prior enzalutamide. A lead-in dose escalation evaluated the recommended phase 2 dose of NLG207 in combination with enzalutamide. Patients received NLG207 via IV infusion every 2 weeks and enzalutamide 160 mg orally once daily.ResultsBetween March 2019 and June 2021, four patients were accrued to the lead-in dose escalation. Two of the four patients were evaluable and both experienced DLTs at the NLG207 12 mg/m² dose level; one DLT was related to a dose delay for noninfective cystitis and myelosuppression, the other a grade 3 noninfective cystitis. Further evaluation of NLG207 in combination with enzalutamide was halted and the study was ultimately terminated. PSA declines from baseline were observed in two patients.ConclusionNLG207 12 mg/m² in combination with enzalutamide was not well tolerated in patients with mCRPC following several lines of the standard of care therapy.ClinicalTrials.gov Identifier{"type":"clinical-trial","attrs":{"text":"NCT03531827","term_id":"NCT03531827"}}NCT03531827.     

Cost-effectiveness Analysis of Innovative Therapy for Patients with Newly Diagnosed Hormone-Sensitive Metastatic Prostate Cancer

BackgroundThe optimal therapeutic strategies for patients with metastatic hormone-sensitive prostate cancer (mHSPC) followed by metastatic castrate-resistant prostate cancer (mCRPC), in terms of cost and effectiveness, remains unknown. This study aims to compare the cost-effectiveness of various potential strategies, from the start of first-line treatment in mHSPC to the death of the patients.MethodsTwo Markov decision-analysis models were developed, one for cohort A “asymptomatic/mildly symptomatic patients in mCRPC”, and one for cohort B “symptomatic patients in mCRPC”. Each strategy reflects daily practice for mHSPC until progression in mCRPC from the start of first treatment regimen with either docetaxel or abiraterone acetate plus prednisone (AA) in mHSPC to the death of the patient. The cost-effectiveness analysis was performed from the French public health care system perspective. Only direct medical costs were included. Survival data were extracted from results of published randomized clinical trials.ResultsFor cohort A, docetaxel followed by AA is the most cost-effective therapeutic strategy (€96,925 for 4.24 life-years). For cohort B, docetaxel followed by docetaxel is the most cost-effective therapeutic strategy (€81,463 for 4.05 life-years). Sensitivity analyses confirmed the robustness of our results except for a price reduction of 70% for AA or enzalutamide.ConclusionOur approach is innovative to the extent that our analysis considers various potential strategies for metastatic prostate cancer (mPC). Our economic evaluation suggests that a price reduction of AA or enzalutamide impacts on the results. This approach must continue, including new drugs for patients with mPC.     

Phase II study of S-1 monotherapy in patients over 75 years of age with advanced gastric cancer (OGSG0404)

Abstract

Background: S-1+cisplatin (CDDP) is the standard treatment for advanced gastric cancer (AGC) in Japan and Korea. However, the usefulness of S-1 based chemotherapy for elderly patients is unclear. Therefore, we conducted a multicenter phase II study of S-1 monotherapy for AGC in elderly patients.

Materials and Methods: Chemotherapy-naïve patients aged over 75 years with AGC were enrolled. The starting dose of S-1 was determined on the basis of body surface area and modified according to the creatinine clearance value. S-1 was administered twice a day during a 4-week period followed by a 2-week rest period.

Results: Thirty-five patients were enrolled. The response rate (RR) was 14·3% and the median overall survival was 14·6 months. Grade 3 or more severe adverse events consisted of anaemia (3%), neutropaenia (3%), anorexia (3%), and fatigue (6%). There were no treatment-related deaths.

Conclusion: Our study indicates that S-1 monotherapy is safe and well tolerated in chemotherapy-naïve elderly patients with AGC, but exerts limited activity when given using a tailor-made dosing strategy based on renal function.     

Clinical activity of abiraterone acetate in patients with metastatic castration-resistant prostate cancer progressing after enzalutamide

BackgroundAbiraterone acetate and enzalutamide both improve outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Optimal sequencing for these agents and whether cross-resistance occurs is unknown.MethodsMulticentre review of patients with mCRPC treated with abiraterone acetate and prednisone after progressing on enzalutamide. Primary objective was to determine abiraterone acetate response.ResultsThirty patients identified from four North American centres. At abiraterone initiation, median age was 70 years (56–84 years); 70% had ECOG performance status of 0–1; all had prior docetaxel. Median prior enzalutamide treatment duration was 41 weeks (6–95 weeks), with 70% (21 of 30) having a ≥30% prostate-specific antigen (PSA) decline. Median abiraterone acetate treatment duration was 13 weeks (1–52). No objective radiographic responses were observed. Median abiraterone time to progression (PSA, objective or symptomatic) was 15.4 weeks [95% confidence interval (CI) 10.7–20.2]. Median overall survival was 50.1 weeks (95% CI 28.3–72.0). Three patients had a ≥30% PSA decline with abiraterone. Two of these patients had PSA progression as best response with prior enzalutamide.ConclusionsIn this study of patients progressing after enzalutamide, treatment with abiraterone was associated with a modest response rate and brief duration of effect. Primary progression on enzalutamide may not preclude a response to abiraterone.     

Lower Fracture Rates in Patients Treated with Radium-223, Abiraterone or Enzalutamide,When Given Concurrently with Bone Health Agents: A Real-World Analysis

BackgroundThe phase 3 trial ERA223 demonstrated an increased fracture rate and no survival advantage for metastatic castration resistant prostate cancer (mCRPC) patients on Radium-223 (Ra-223) with abiraterone, leading to regulatory restrictions on combination therapy. However, less than half of trial patients received bone health agents (BHA). We reviewed electronic health record (EHR) data evaluating fracture rates for patients on BHA receiving Ra-223, androgen deprivation therapy and either abiraterone or enzalutamide.Patients and MethodsWe conducted a retrospective, cohort analysis of EHR data of mCRPC patients on Ra-223 treated at a single community center by a single provider between 2010 and 2018. The primary objective was evaluating fracture rates for patients on BHA receiving Ra-223 and abiraterone. We conducted a secondary analysis for enzalutamide.ResultsOne hundred seventy-seven patients received Ra-223 concurrently with abiraterone or enzalutamide between November 2010 and August 2018. The median age was 73 at first Ra-223 dose (range 40-93). The median follow-up time from last Ra-223 dose was 30 months (range 2-106). One hundred sixty-four patients (93%) received BHAs. One hundred fifty-nine patients (89%) were on a BHA before and/or during Ra-223. Sixty-seven patients received denosumab (38%), 63 received zoledronic acid (36%), and 29 received both nonconcurrently (16%). Eleven patients (6.2%) experienced a fracture after starting Ra-223, 9 of which occurred while on prior and/or concurrent BHA. We observed a 5.7% fracture rate for mCRPC patients who received combination therapy and denosumab or zoledronic acid.ConclusionThis real-world analysis demonstrating a low fracture rate in patients with mCRPC receiving a BHA while on Ra-223 and abiraterone or enzalutamide may inform current clinical practice.     

Phase II trial of the PI3 kinase inhibitor buparlisib (BKM-120) with or without enzalutamide in men with metastatic castration resistant prostate cancer

BackgroundPhosphatidylinositol-3-kinase (PI3K) and androgen receptor pathway activation is common in metastatic castration resistant prostate cancer (mCRPC). Buparlisib is an oral, pan-class I PI3 kinase inhibitor.MethodsThis was a multisite single arm phase II trial of buparlisib 100 mg ± enzalutamide daily in men with mCRPC whose disease progressed on or who were not candidates for docetaxel. The primary end-point was the rate of radiographic/clinical progression-free survival (PFS) at 6 months.ResultsThirty men were accrued: 67% post-docetaxel; median prostate specific antigen (PSA) was 70 ng/dl, 83% had ≥4 prior therapies for mCRPC; 43% received concurrent enzalutamide. The final 6 month PFS rate was estimated to be 10% (95% confidence interval 2.5–23.6%). Median PFS was 1.9 months and was 3.5 months with concurrent enzalutamide. Median overall survival was 10.6 months. Concurrent enzalutamide led to a five-fold reduction in buparlisib concentrations. PSA declines were observed in 23%; no patients achieved a ≥50% decline, and no radiographic responses were observed. Severe adverse events occurred in four men including respiratory infection and multi-organ failure, urinary tract obstruction, confusion and one seizure in the setting of a new central nervous system (CNS) metastasis. Grade III adverse events were seen in 43% of patients; common toxicities included grade I–II weight loss, diarrhoea, nausea, fatigue, anorexia, rash, hyperglycemia and anxiety/mood disorders.ConclusionsBuparlisib did not demonstrate significant activity in men with mCRPC, suggesting that PI3K inhibition is not sufficient to reverse resistant mCRPC progression. Future studies of PI3K pathway inhibitors with concurrent enzalutamide should develop optimal dosing and focus on selected patients more likely to benefit.     

U.S. Food and Drug Administration Approval Summary: Enzalutamide for the Treatment of Patients With Chemotherapy‐Naïve Metastatic Castration‐Resistant Prostate Cancer

The U.S. Food and Drug Administration approved enzalutamide for the treatment of patients with chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). At the prespecified interim analysis, a statistically significant improvement in overall survival was demonstrated for patients in the enzalutamide arm compared with patients in the placebo arm. The overall benefit-risk profile supports the expanded indication for enzalutamide. On September 10, 2014, the U.S. Food and Drug Administration approved enzalutamide for the treatment of patients with chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). Enzalutamide was initially approved in 2012 for use in patients with mCRPC who had previously received docetaxel. The current approval was based on the results of a randomized, placebo-controlled, double-blind trial conducted in 1,717 asymptomatic or minimally symptomatic patients with chemotherapy-naïve mCRPC. Patients were assigned to receive either enzalutamide 160 mg or placebo orally once daily. The coprimary endpoints were overall survival (OS) and radiographic progression-free survival (rPFS), which was assessed by independent central radiology review. At the prespecified interim analysis, a statistically significant improvement in OS was demonstrated for patients in the enzalutamide arm compared with patients in the placebo arm (hazard ratio [HR], 0.71; 95% confidence interval [CI], 0.60–0.84). The median OS was 32.4 and 30.2 months in the enzalutamide and placebo arms, respectively. A statistically significant prolongation of rPFS was observed in patients in the enzalutamide arm (HR, 0.17; 95% CI, 0.14–0.21). In addition, the time to initiation of cytotoxic chemotherapy was prolonged in the enzalutamide arm (HR, 0.35; 95% CI, 0.30–0.40), with median times of 28.0 and 10.8 months in the enzalutamide and placebo arms, respectively. The safety profile was similar to that previously reported for enzalutamide. Adverse reactions of interest included seizure, hypertension, and falls. Enzalutamide should be discontinued if a seizure occurs during treatment. The overall benefit-risk profile supports the expanded indication for enzalutamide.

Implications for Practice:

This new approval expands the enzalutamide indication, allowing health care providers and patients to use enzalutamide for the treatment of metastatic castration-resistant prostate cancer either before or after cytotoxic chemotherapy.     

Tasquinimod: A Novel Angiogenesis Inhibitor–Development in Prostate Cancer

Castration resistant prostate cancer (CRPC) treatment has been revolutionized over the past few years by the approval of novel therapies including cabazitaxel, sipuleucel-T, abiraterone and enzalutamide. Though androgen deprivation and chemotherapy remain the main therapeutic approaches for this disease, a series of targeted agents is also in development for the treatment of CRPC. Tasquinimod is a quinolone-3-carboxamide with antiangiogenic and antitumor activity in preclinical models of prostate cancer. A recent Phase II trial with this agent has demonstrated a significant clinical activity in asymptomatic or minimally symptomatic, chemotherapy-naïve, CRPC patients. A confirmatory Phase III trial of tasquinimod in prostate cancer is underway. Because of its antiangiogenic and immunomodulatory properties tasquinimod represents a novel targeted therapy with a unique mechanism of action.     

Early PSA response is an independent prognostic factor in patients with metastatic castration-resistant prostate cancer treated with next-generation androgen pathway inhibitors

BackgroundThe optimal use of new therapies in metastatic castration-resistant prostate cancer (mCRPC) remains to be clarified. Prostate-specific antigen (PSA) response used as a pharmacodynamic end-point may help identify patients with early resistance to new androgen receptor-pathway inhibitors. We aimed to determine the clinical significance of early PSA response (EPR) during therapy with enzalutamide, abiraterone acetate (AA) and orteronel in mCRPC.MethodsData from patients recruited in clinical trials were studied. PSA values were obtained at baseline and 28 d after treatment initiation. EPR defined as a decline >50% from baseline was calculated according to the Prostate Cancer Working Group 2 criteria. The effects of clinical characteristics on radiographic progression-free survival (rPFS) and overall survival (OS) were examined using the Cox model.ResultsEPR was assessed in 118 patients treated in clinical trials and was found to be associated with longer rPFS and OS (P < 0.0001 for both). Median rPFS was 13.9 and 5.6 months (hazard ratio [HR]:0.38, P < 0.001) for patients with and without an EPR, respectively. Median OS was 32.2 months in patients with an EPR and 15.9 months in patients without an EPR (HR: 0.4, P < 0.01). EPR remained prognostic for OS in multivariate analyses (HR: 0.5, p = 0.009) that included validated pre-therapeutic prognostic factors for mCRPC. Prognostic values of EPR for rPFS and OS were confirmed in an independent cohort of 95 AA-treated non-trial patients.ConclusionsEPR is an independent prognostic factor in patients with mCRPC treated with next-generation androgen pathway inhibitors and may be useful for the therapeutic management of these patients.