Antitumour activity of docetaxel following treatment with the CYP17A1 inhibitor abiraterone: clinical evidence for cross-resistance?

Metastatic castration-resistant prostate cancer: time for innovation

Androgen deprivation is the mainstay of advanced prostate cancer treatment. Despite initial responses, almost all patients progress to castration-resistant prostate cancer (CRPC). The understanding of the biology of CRPC and the evidence that CRPC still remains driven by androgen receptor signaling led to the discovery of new therapeutic targets. In the last few years, large Phase III trials showed improvements in survival and outcomes and led to the approval of a CYP17 inhibitor (abiraterone), an androgen receptor antagonist (enzalutamide), the taxane cabazitaxel, an α-emitter (radium-223), the bone resorption-targeting drug denosumab and an immunotherapy (sipuleucel-T). This article describes the molecular mechanisms underlying castration resistance, discusses recent and ongoing trials and offers some insights into identifying the best sequence of new drugs.

What do we know about treatment sequencing of abiraterone, enzalutamide, and chemotherapy in metastatic castration-resistant prostate cancer?

PURPOSE

To present a systematic review of the different therapeutic sequences in metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Evidence acquisition on therapeutic sequences in mCRPC was performed by a MEDLINE search using combination of the following key words: "prostate cancer," "metastatic," "castration resistant," "enzalutamide," "abiraterone," "treatment sequencing," "cabazitaxel," "docetaxel." A total of 17 studies were included for analysis.

RESULTS

Different sequences have been reported for the treatment of mCRPC: docetaxel after abiraterone, cabazitaxel after docetaxel and abiraterone, abiraterone after cabazitaxel and docetaxel, abiraterone after docetaxel and enzalutamide, and enzalutamide after docetaxel and abiraterone. There are arguments from the preclinical observations suggesting a cross-resistance between docetaxel and abiraterone, and between abiraterone and enzalutamide in mCRPC. Despite limitations, several retrospective clinical reports support these data.

CONCLUSION

No study of high level of evidence is available to support any recommendation on sequential treatment for mCRPC. There are only clues that prospective clinical studies need to confirm.

Androgen receptor splice variants circumvent AR blockade by microtubule-targeting agents

Docetaxel-based chemotherapy is established as a first-line treatment and standard of care for patients with metastatic castration-resistant prostate cancer. However, half of the patients do not respond to treatment and those do respond eventually become refractory. A better understanding of the resistance mechanisms to taxane chemotherapy is both urgent and clinical significant, as taxanes (docetaxel and cabazitaxel) are being used in various clinical settings. Sustained signaling through the androgen receptor (AR) has been established as a hallmark of CRPC. Recently, splicing variants of AR (AR-Vs) that lack the ligand-binding domain (LBD) have been identified. These variants are constitutively active and drive prostate cancer growth in a castration-resistant manner. In taxane-resistant cell lines, we found the expression of a major variant, AR-V7, was upregulated. Furthermore, ectopic expression of two clinically relevant AR-Vs (AR-V7 and ARV567es), but not the full-length AR (AR-FL), reduced the sensitivities to taxanes in LNCaP cells. Treatment with taxanes inhibited the transcriptional activity of AR-FL, but not those of AR-Vs. This could be explained, at least in part, due to the inability of taxanes to block the nuclear translocation of AR-Vs. Through a series of deletion constructs, the microtubule-binding activity was mapped to the LBD of AR. Finally, taxane-induced cytoplasm sequestration of AR-FL was alleviated when AR-Vs were present. These findings provide evidence that constitutively active AR-Vs maintain the AR signaling axis by evading the inhibitory effects of microtubule-targeting agents, suggesting that these AR-Vs play a role in resistance to taxane chemotherapy.

Drug therapies for metastatic castration-resistant prostate cancer

Management of metastatic castration-resistant prostate cancer has changed markedly over the last decade with major shifts in the treatment paradigm, although ultimately still will progress despite currently available therapies. The sequencing or combination of these agents is an area of active investigation, since definitive prospective randomized trials to define the optimal choice of drug sequence have yet to be done or resulted. This article will highlight pivotal trials for currently approved therapies for metastatic castration-resistant prostate cancer and a suggestion for sequencing of these agents, as well as highlighting investigations using novel therapies for advanced prostate cancer.

Targeting molecular resistance in castration-resistant prostate cancer

Multiple mechanisms of resistance contribute to the inevitable progression of hormone-sensitive prostate cancer to castration-resistant prostate cancer (CRPC). Currently approved therapies for CRPC include systemic chemotherapy (docetaxel and cabazitaxel) and agents targeting the resistance pathways leading to CRPC, including enzalutamide and abiraterone. While there is significant survival benefit, primary and secondary resistance to these therapies develops rapidly. Up to one-third of patients have primary resistance to enzalutamide and abiraterone; the remaining patients eventually progress on treatment. Understanding the mechanisms of resistance resulting in progression as well as identifying new targetable pathways remains the focus of current prostate cancer research. We review current knowledge of mechanisms of resistance to the currently approved treatments, development of adjunctive therapies, and identification of new pathways being targeted for therapeutic purposes.

New developments in the treatment of castration resistant prostate cancer

In the past 5 years, the treatment and understanding of metastatic castrate resistant prostate cancer (CRPC) have improved dramatically. Our understanding of the mechanisms of castration resistance has allowed for the development of new drugs to target prostate cancer, and our understanding of genetic mutations may give us new tools with which to more accurately diagnose and be able to predict the course of this heterogeneous disease. This article summarizes the recent advances in the understanding of the development of CRPC, as well as the new drugs and targets, which have evolved from this basic research.

Comparative analysis of the effectiveness of abiraterone before and after docetaxel in patients with metastatic castration-resistant prostate cancer

AIM: To study the efficacy and safety of abiraterone in patients with and without prior chemotherapy.

METHODS: The databases including PubMed and abstracts presented at the American Society of Clinical Oncology meetings up to April 2014 were systematically searched. Eligible studies included randomized controlled trials (RCTs) in which abiraterone plus prednisone was compared to placebo plus prednisone in metastatic castration-resistant prostate cancer (CRPC) patients. The summary incidence, relative risk, hazard ratio and 95%CI were calculated using random or fixed-effects models. Heterogeneity test was performed to test between-study differences in efficacy and toxicity.

RESULTS: A total of two phase III RCTs were included in our analysis, with metastatic CPRC patients before (n = 1088) and after chemotherapy (n = 1195). Prior chemotherapy did not significantly alter the effect of abiraterone on overall survival (P = 0.92) and prostate-specific antigen (PSA) progression-free survival (P = 0.13), but reduced its effect on radiographic-progression-free survival (P = 0.04), objective response rate (P < 0.001), and PSA response rate (P < 0.001). Prior chemotherapy significantly increased the specific risk of fluid retention and edema (P < 0.001) and hypokalemia (P < 0.001), but decreased the risk of all-grade hypertension (P < 0.001) attributable to abiraterone. There was no significant difference of cardiac disorders associated with abiraterone between the two settings (P = 0.58).

CONCLUSION: Prior chemotherapy may reduce the effectiveness of abiraterone in patients with metastatic CRPC.

Should docetaxel be standard of care for patients with metastatic hormone-sensitive prostate cancer? Pro and contra

Following the results of the TAX-327 study, questions have been raised as to whether administering chemotherapy to men with prostate cancer before symptomatic disease progression when receiving standard hormonal treatment can improve the duration and quality of patient survival. The GETUG-AFU-15 and CHAARTED studies both assessed the efficacy and tolerability of androgen deprivation therapy (ADT) with or without docetaxel in men with metastatic hormone-naive prostate cancer. Both studies included a mix of patients with de novo metastatic disease (∼75%) and patients who developed metastases following treatment of localized disease. A short course of ADT was allowed in both trials prior to accrual. Key differences between the two studies include the number of patients with high-volume metastases (GETUG-AFU-15: 52%; CHAARTED: 65%) and number of docetaxel cycles (GETUG-AFU-15: up to nine cycles; CHAARTED six cycles). Both studies reported an improvement in progression-free survival with docetaxel plus ADT versus ADT alone. The GETUG-AFU-15 did not find a significant difference in the primary end point of overall survival (OS) {hazard ratio (HR) 0.9 [95% confidence interval (CI) 0.7-1.2]; P = 0.44} for ADT plus docetaxel versus ADT alone. The CHAARTED study met the primary end point of OS [HR 0.61 (95% CI 0.47-0.80); P = 0.0003], and in a subset analysis reported the greatest improvement in OS for patients with high-volume disease [HR 0.60 (95% CI 0.45-0.81); P = 0.0006]. The following article debates the results from the GETUG-AFU-15 and CHAARTED studies and asks whether medical practice should be changed for patients with metastatic hormone-naive prostate cancer based on the results of one positive study.

Management of patients with advanced prostate cancer: recommendations of the St Gallen Advanced Prostate Cancer Consensus Conference (APCCC) 2015

The first St Gallen Advanced Prostate Cancer Consensus Conference (APCCC) Expert Panel identified and reviewed the available evidence for the ten most important areas of controversy in advanced prostate cancer (APC) management. The successful registration of several drugs for castration-resistant prostate cancer and the recent studies of chemo-hormonal therapy in men with castration-naïve prostate cancer have led to considerable uncertainty as to the best treatment choices, sequence of treatment options and appropriate patient selection. Management recommendations based on expert opinion, and not based on a critical review of the available evidence, are presented. The various recommendations carried differing degrees of support, as reflected in the wording of the article text and in the detailed voting results recorded in supplementary Material, available at Annals of Oncology online. Detailed decisions on treatment as always will involve consideration of disease extent and location, prior treatments, host factors, patient preferences as well as logistical and economic constraints. Inclusion of men with APC in clinical trials should be encouraged.

Expert opinion on first-line therapy in the treatment of castration-resistant prostate cancer

Treatment of metastatic castration-resistant prostate cancer (mCRPC) has been revolutionized in recent years. It is well known that androgen receptor is still active in most patients with disease progression and serum testosterone levels <50 ng/dL. Moreover, further hormonal maneuvers, either through decreasing androgen levels (abiraterone) or by targeting the androgen receptor (AR) pathway (enzalutamide), prolong survival. In addition, a new cytostatic able to overcome docetaxel resistance, cabazitaxel, and the radioisotope radium 223 have been incorporated to the armamentarium of mCRPC. mCRPC is not only a heterogeneous tumor, it changes over time developing neuroendocrine features or selection of clones resistant to hormonal maneuvers. In addition, the multiplicity of current treatments, make it necessary to design algorithms that help the specialist to choose the most appropriate treatment for a particular patient. The lack of randomized trials comparing face to face the different available options limit the scope of this review. In this article, the authors describe the prognostic factors for first line therapy in patients with mCRPC, and propose a treatment algorithm for mCRPC based on the levels of scientific evidence available and, if not available, on the consensus between medical professionals. Finally, the panel discuss how to define progressive disease in the setting of mCRPC and treatment with targeted therapies.

Targeting the adaptive molecular landscape of castration-resistant prostate cancer

Castration and androgen receptor (AR) pathway inhibitors induce profound and sustained responses in advanced prostate cancer. However, the inevitable recurrence is associated with reactivation of the AR and progression to a more aggressive phenotype termed castration-resistant prostate cancer (CRPC). AR reactivation can occur directly through genomic modification of the AR gene, or indirectly via co-factor and co-chaperone deregulation. This mechanistic heterogeneity is further complicated by the stress-driven induction of a myriad of overlapping cellular survival pathways. In this review, we describe the heterogeneous and evolvable molecular landscape of CRPC and explore recent successes and failures of therapeutic strategies designed to target AR reactivation and adaptive survival pathways. We also discuss exciting areas of burgeoning anti-tumour research, and their potential to improve the survival and management of patients with CRPC.

Androgen pathway resistance in prostate cancer and therapeutic implications

INTRODUCTION

Metastatic prostate cancer is an incurable disease that is treated with a variety of hormonal therapies targeting various nodes of the androgen receptor (AR) pathway. Invariably patients develop resistance and become castration resistant. Common treatments for castration-resistant disease include novel hormonal therapies, such as abiraterone and enzalutamide, chemotherapy, immunotherapy and radiopharmaceuticals. As this disease generally remains incurable, understanding the molecular underpinnings of resistance pathways is critical in designing therapeutic strategies to delay or overcome such resistance.

AREAS COVERED

This review will explore the resistance mechanisms relevant to hormonal agents, such as AR-V7 expression and others, as well as discussing new approaches being developed to treat patients with castration-resistant prostate cancer that take advantage of these new insights. A literature search was performed to identify all published clinical trials related to androgen therapy mechanisms of drug resistance in metastatic castration-resistant prostate cancer.

EXPERT OPINION

Androgen therapy resistance mechanisms are varied, and include modification of all nodes in the androgen signaling pathway. The optimal treatment for men with relapsed metastatic castration-resistant prostate cancer is uncertain at this time. The authors recommend using available clinical data to guide treatment decision making until more specific biomarkers are clinically available.

Updated recommendations from the Spanish Oncology Genitourinary Group for the treatment of patients with metastatic castration-resistant prostate cancer

Prostate cancer is the most prevalent male urogenital malignancy. Approximately 30% of patients with prostate cancer will develop advanced disease. Androgen deprivation therapy achieves disease control in about 90% of these patients, but the majority of them will eventually develop progressive disease, a status called castration-resistant prostate carcinoma (CRPC). However, in recent years, several new therapy strategies, such as immunotherapy, hormonal manipulations, chemotherapy agents and some bone-targeted therapies, have demonstrated an improvement in terms of overall survival in controlled trials. In 2012, the Spanish Oncology Genitourinary Group (SOGUG) published its recommendations for the treatment of patients with CRPC. Due to the recent appearance of important new data and the complexity of decision-making in this field, SOGUG herein provides updated recommendations for the treatment of patients with metastatic prostate cancer.

Prospective evaluation of low-dose ketoconazole plus hydrocortisone in docetaxel pre-treated castration-resistant prostate cancer patients

BACKGROUND

Ketoconazole is a well-known CYP17-targeted systemic treatment for castration-resistant prostate cancer (CRPC). However, most of the published data has been in the pre-chemotherapy setting; its efficacy in the post-chemotherapy setting has not been as widely described. Chemotherapy-naïve patients treated with attenuated doses of ketoconazole (200-300 mg three times daily) had PSA response rate (>50% decline) of 21-62%. We hypothesized that low-dose ketoconazole would likewise possess efficacy and tolerability in the CRPC post-chemotherapy state.

METHODS

Men with CRPC and performance status 0-3, adequate organ function and who had received prior docetaxel were treated with low-dose ketoconazole (200 mg orally three times daily) and hydrocortisone (20 mg PO qAM and 10 mg PO qPM) until disease progression. Primary endpoint was PSA response rate (>50% reduction from baseline) where a rate of 25% was to be considered promising for further study (versus a null rate of <5%); 25 patients were required. Secondary endpoints included PSA response >30% from baseline, progression-free survival (PFS), duration of stable disease and evaluation of adverse events (AEs).

RESULTS

Thirty patients were accrued with median age of 72 years (range 55-86) and median pre-treatment PSA of 73 ng ml(-1) (range 7-11,420). Twenty-nine patients were evaluable for response and toxicity. PSA response (>50% reduction) was seen in 48% of patients; PSA response (>30% reduction) was seen in 59%. Median PFS was 138 days; median duration of stable disease was 123 days. Twelve patients experienced grade 3 or 4 AEs. Of the 17 grade 3 AEs, only 3 were attributed to treatment. None of the two grade 4 AEs were considered related to treatment.

CONCLUSIONS

In docetaxel pre-treated CRPC patients, low-dose ketoconazole and hydrocortisone is a well-tolerated, relatively inexpensive and clinically active treatment option. PSA response to low-dose ketoconazole appears historically comparable to that of abiraterone in this patient context. A prospective, randomized study of available post-chemotherapy options is warranted to assess comparative efficacy.

Sequencing of agents in castration-resistant prostate cancer

Until 2010, docetaxel was the only agent with proven survival benefit for castration-resistant prostate cancer. The development of cabazitaxel, abiraterone acetate, enzalutamide, radium-223, and sipuleucel-T has increased the number of treatment options. Because these agents were developed concurrently within a short period of time, prospective data on their sequential use efficacy are scarce. The challenge now is to reach a consensus on the best way to sequence effective treatments, ideally by the use of an approach specific to patient subgroups. However, the absence of robust surrogates of survival and the lack of predictive biomarkers makes data for the sequential use of these agents difficult to obtain and interpret.

A multicenter retrospective analysis of sequential treatment of abiraterone acetate followed by docetaxel in Japanese patients with metastatic castration-resistant prostate cancer

OBJECTIVE

Abiraterone acetate and docetaxel are promising treatment options for metastatic castration-resistant prostate cancer patients. However, the optimal sequencing of these agents is unclear, and no previous reports discuss Japanese metastatic castration-resistant prostate cancer patients. The purpose of this analysis is to reveal the outcomes of Japanese metastatic castration-resistant prostate cancer patients treated with abiraterone acetate followed by docetaxel.

METHODS

We retrospectively reviewed Japanese Phase 1 and Phase 2 trials of metastatic castration-resistant prostate cancer patients treated with abiraterone acetate until disease progression and subsequently treated with docetaxel. The primary outcome measure was the rates of prostate-specific antigen declines ≧30 and ≧50%, respectively, with docetaxel. Secondary outcome measures included progression-free survival with docetaxel, and overall survival after initiation of abiraterone acetate and docetaxel. We performed correlation analysis between previous prostate-specific antigen response to abiraterone acetate and subsequent prostate-specific antigen response to docetaxel.

RESULTS

We identified 15 patients had experienced disease progression with abiraterone acetate and subsequently were treated with docetaxel. Prostate-specific antigen declines ≧30 and ≧50% with docetaxel were observed in five patients (33%) and two patients (13%), respectively. The median progression-free survival with docetaxel was 3.7 months (95% confidence interval: 2.9-4.6). The median overall survival from initiation of docetaxel and abiraterone acetate were 14.4 months (95% confidence interval: 6.3-22.4), and 25.7 months (95% confidence interval: 20.1-30.7), respectively. No significant correlation was observed between these prostate-specific antigen responses (Pearson r = 0.206, P = 0.46).

CONCLUSION

The efficacy of docetaxel in Japanese mCRPC patients that was resistant to abiraterone acetate was modest. The prostate-specific antigen response to previous abiraterone acetate could not predict the efficacy of subsequent docetaxel. Larger prospective trials are needed to validate these findings.

Abiraterone acetate in patients with metastatic castration-resistant prostate cancer: long term outcome of the Temporary Authorization for Use programme in France

BACKGROUND

COU-AA-301 trial has proved that abiraterone acetate (AA), a selective inhibitor of androgen biosynthesis, improved overall survival (OS) of patients with metastatic castration resistant prostate cancer (mCRPC) after a first line of docetaxel. Based on this result, a Temporary Authorization for Use (TAU) was performed between December 2010 and July 2011 to provide patients with mCRPC the opportunity to receive AA before its commercialization. The aim of this study was to evaluate safety and efficacy of AA treatment in this TAU.

METHODS

Between December 2010 and July 2011, we conducted an ambispective, multicentric cohort study and investigated data from 20 centres participating to the AA TAU for patients presenting mCRPC and already treated by a first line of chemotherapy (CT). Statistical analyses of the data were performed using the Stata software v13 to identify predictive and prognostic factors.

RESULTS

Among the 408 patients, 306 were eligible with a follow-up at 3 years. Median OS was 37.1 months from beginning of CT and 14.6 months from AA introduction. 211 patients (69%) received ≥ 3 months of AA and 95 patients (31%) were treated less than 3 months. In the multivariate analyses, duration of AA was significantly correlated with PSA decrease at 3 months. Additionally, shorter time under AA treatment, presence of multiple sites of metastasis and previous hormonal treatment duration were three independent factors associated with poorer OS. At the time of analysis ten patients were still under treatment for more than 3 years.

CONCLUSIONS

Biochemical response monitored by PSA changes at 3 months is a strong predictive factor for AA treatment duration. Some high responders' patients could beneficiate from AA for more than 3 years.

Phase 1/2 study of orteronel (TAK-700), an investigational 17,20-lyase inhibitor, with docetaxel-prednisone in metastatic castration-resistant prostate cancer

BACKGROUND

Docetaxel-prednisone (DP) is an approved therapy for metastatic castration-resistant prostate cancer (mCRPC). Orteronel (TAK-700) is an investigational, selective, non-steroidal inhibitor of 17,20-lyase, a key enzyme in androgenic hormone production. This phase 1/2 study evaluated orteronel plus DP in mCRPC patients.

METHODS

Adult men with chemotherapy-naïve mCRPC, serum prostate-specific antigen (PSA) ≥5 ng/mL, and serum testosterone <50 ng/dL received oral orteronel 200 or 400 mg twice-daily (BID) in phase 1 to determine the recommended dose for phase 2, plus intravenous docetaxel 75 mg/m(2) every 3 weeks, and oral prednisone 5 mg BID. Phase 2 objectives included safety, pharmacokinetics, and efficacy.

RESULTS

In phase 1 (n = 6, orteronel 200 mg; n = 8, orteronel 400 mg), there was one dose-limiting toxicity of grade 3 febrile neutropenia at 400 mg BID. This dose was evaluated further in phase 2 (n = 23). After 4 cycles, 68, 59, and 23% of patients achieved ≥30, ≥50, and ≥90% PSA reductions, respectively; median best PSA response was -77%. Seven of 10 (70%) RECIST-evaluable patients achieved objective partial responses. Median time to PSA progression and radiographic disease progression was 6.7 and 12.9 months, respectively. Dehydroepiandrosterone-sulfate (DHEA-S) and testosterone levels were rapidly and durably reduced. Common adverse events were fatigue (78%), alopecia (61%), diarrhea (48%), nausea (43%), dysgeusia (39%), and neutropenia (39%). Orteronel and docetaxel pharmacokinetics were similar alone and in combination.

CONCLUSIONS

Orteronel plus DP was tolerable, with substantial reductions in PSA, DHEA-S, and testosterone levels, and evidence for measurable disease responses.

Metastatic castration-resistant prostate cancer (CRPC): preclinical and clinical evidence for the sequential use of novel therapeutics

With five novel therapies shown to improve survival in metastatic castration-resistant prostate cancer (CRPC) in the last 3 years, patients are now living longer and experiencing better quality of life. Since docetaxel became standard of care for men with symptomatic metastatic CRPC, three artificial treatment "spaces" have emerged for prostate cancer drug development: pre-docetaxel, docetaxel combinations, and following docetaxel. Multiple therapies are currently under development in both early and late stage CRPC. Additionally, the novel agents abiraterone, radium-223, cabazitaxel, and enzalutamide have all been approved in the post-docetaxel setting. Strategies for patient selection and treatment sequencing are therefore urgently required. In this comprehensive review, we will summarize the preclinical and clinical data available with regards to sequencing of the novel treatments for CRPC.

Importance of cycles of chemotherapy and postdocetaxel novel therapies in metastatic castration-resistant prostate cancer

Purpose

With the emergence of various novel therapies including new generation taxane and androgen-targeted therapies, the optimal sequence of systemic treatment in metastatic castration-resistant prostate cancer (mCRPC) patients remains to be defined. Our aim is to investigate the impact of duration of docetaxel-based chemotherapy and postdocetaxel treatment in mCRPC patients.

Methods

The medical data of 57 Chinese mCRPC patients who received docetaxel-based chemotherapy in two oncology centers between 2003 and 2012 were reviewed. The treatment efficacy and toxicity were determined. The potential determinants of efficacy were also determined.

Results

Fifty-seven patients (median age 66 years, range 51–82 years) were given docetaxel-based chemotherapy, of whom 48 (84.2%) received 3-weekly docetaxel (52.5–75 mg/m²) and nine (15.8%) received weekly docetaxel (35 mg/m²). Postdocetaxel treatments were received by 31 (57.4%) patients, including abiraterone in 13 patients and cabazitaxel in one patient. The median follow-up time was 14.3 months. The median overall survival (OS) and progression-free survival were 20.8 months and 5.8 months, respectively. In multivariate analysis, eight cycles or more of chemotherapy [hazard ratio (HR) = 0.151, P < 0.0358], use of postdocetaxel treatment (HR = 0.346, P = 0.0005), and hemoglobin level of <10 (HR = 5.224, P < 0.0001) were independent determinants of OS. Patients who had received abiraterone and cabazitaxel as postdocetaxel treatment had significantly longer OS compared with those who received other postdocetaxel treatments (including rechallenge of docetaxel) and those who did not receive any postdocetaxel treatment (35.3 months vs. 20.8 months vs. 15.3 months, P = 0.00057).

Conclusions

The results suggest that maximizing exposure to docetaxel-based chemotherapy followed by novel therapies would have a favorable survival impact on mCRPC patients.

Sequencing current therapies in the treatment of metastatic prostate cancer

The standard treatment for metastatic prostate cancer is androgen deprivation therapy. However, progressive, metastatic disease usually develops, giving rise to metastatic castration-resistant prostate cancer (mCRPC). Great improvements have been made recently in the management of mCRPC, with current approved treatments including chemotherapy, androgen receptor-targeted agents, immunotherapies and radiopharmaceuticals. While the emergence of multiple effective therapies is encouraging, devising a treatment strategy can be difficult and it is becoming increasingly important, and challenging, to identify factors that influence the ideal timing of specific therapies. Considering where to place these agents in the treatment schedule of mCRPC, or whether these agents should be sequenced or combined to derive the optimal benefit for the patient, is not yet clear. Furthermore, cross-resistance may exist between these agents, which may ultimately influence treatment decisions and sequence choices. Preliminary data are emerging regarding the safety and activity for sequential treatment regimens, but there are currently no prospective studies. As prostate cancer is highly heterogeneous clinically, it is likely that no single treatment sequence will be optimal for all patients. However, at present, there are no validated biomarkers to guide individualized treatment for mCRPC. Here we review available data for the different mCRPC treatments, discussing potential sequencing of agents and possible cross-resistance or synergy among the recently approved and emerging therapies.

Rechallenge of docetaxel combined with epirubicin given on a weekly schedule in advanced castration-resistant prostate cancer patients previously exposed to docetaxel and abiraterone acetate: a single-institution experience

The aim of this paper was to evaluate the activity and tolerability of weekly docetaxel (D) combined with weekly epirubicin (EPI) in patients with advanced castrate-resistant prostate cancer (CRPC) previously exposed to D and abiraterone acetate (AA). Locally advanced or metastatic CRPC patients with 0-2 performance status, who had progressed after D and AA therapy, were included in the study. Previous treatment with chemotherapy agent cabazitaxel was also admitted. Treatment consisted of D 30 mg/m(2) intravenously (i.v.) and EPI 30 mg/m(2) i.v., every week (D/EPI). Chemotherapy was administered until disease progression or unacceptable toxicity. In our institution, twenty-six patients received D/EPI: their median age was 72 years (range 59-83 years). Twenty-three (88.5%) patients had bone metastases. A decrease in PSA levels ≥50% was observed in seven patients (26.9%, 95% CI: 0.11-0.47); of these, five had achieved a ≥50% PSA response during prior first-line D and six had achieved a PSA response during prior AA Among the subjects who were symptomatic at baseline, pain was reduced in nine patients (38.1%) with a significant decrease in analgesic use. Median progression-free survival was 4.4 months (95% CI, 3-5.2), and median overall survival was 10.7 months (95% CI, 8.9-18.4). Treatment was well tolerated and no grade 4 toxicities were observed. Our findings suggest that weekly D/EPI is feasible and active in heavily pretreated advanced CRPC patients and seem to support the hypothesis that the addition of EPI to D may lead to overcome the resistance to D in a subgroup of patients.

Rechallenge of docetaxel combined with epirubicin given on a weekly schedule in advanced castration-resistant prostate cancer patients previously exposed to docetaxel and abiraterone acetate: a single-institution experience

The aim of this paper was to evaluate the activity and tolerability of weekly docetaxel (D) combined with weekly epirubicin (EPI) in patients with advanced castrate-resistant prostate cancer (CRPC) previously exposed to D and abiraterone acetate (AA). Locally advanced or metastatic CRPC patients with 0-2 performance status, who had progressed after D and AA therapy, were included in the study. Previous treatment with chemotherapy agent cabazitaxel was also admitted. Treatment consisted of D 30 mg/m(2) intravenously (i.v.) and EPI 30 mg/m(2) i.v., every week (D/EPI). Chemotherapy was administered until disease progression or unacceptable toxicity. In our institution, twenty-six patients received D/EPI: their median age was 72 years (range 59-83 years). Twenty-three (88.5%) patients had bone metastases. A decrease in PSA levels ≥50% was observed in seven patients (26.9%, 95% CI: 0.11-0.47); of these, five had achieved a ≥50% PSA response during prior first-line D and six had achieved a PSA response during prior AA Among the subjects who were symptomatic at baseline, pain was reduced in nine patients (38.1%) with a significant decrease in analgesic use. Median progression-free survival was 4.4 months (95% CI, 3-5.2), and median overall survival was 10.7 months (95% CI, 8.9-18.4). Treatment was well tolerated and no grade 4 toxicities were observed. Our findings suggest that weekly D/EPI is feasible and active in heavily pretreated advanced CRPC patients and seem to support the hypothesis that the addition of EPI to D may lead to overcome the resistance to D in a subgroup of patients.

Enzalutamide: a new prostate cancer targeted therapy against the androgen receptor

Enzalutamide (MDV3100), an androgen receptor-signalling inhibitor, represents the most recent compound added to the therapeutic armamentarium for the treatment of metastatic castration-resistant prostate cancer (mCRPC) who progressed to docetaxel. The anti-tumour activity and safety of enzalutamide has been demonstrated in a phase III clinical trial, showing a benefit in overall survival, which was the primary endpoint. There are no head-to-head studies comparing the different treatment options in this subset of patients. In this article, most relevant data published in the literature have been reviewed, with special attention to the therapeutic alternatives currently available for postdocexatel mCRPC patients, emphasising the mechanisms of action of the different drugs, efficacy and quality of life-related aspects.

Targeting extra-gonadal androgens in castration-resistant prostate cancer

Metastatic castration resistant prostate cancer (CRPC) is associated with a rise in PSA, suggesting an increase in transcription of steroid receptor regulated genes. The efficacy of the new anti-androgen therapies abiraterone and enzalutamide, that target extra-gonadal activation of androgen signaling, confirm CRPC's addiction to genes regulated by the androgen receptor (AR). However, patients invariably progress and develop resistance. This review focuses on mechanisms of drug resistance associated with the AR and steroidogenesis in CRPC. Understanding this persistent dependency and adaptation to the androgen axis in CRPC will lead to an understanding of resistance to new licensed therapies and to novel drug discovery, ultimately improving clinical outcome in CRPC. This article is part of a Special Issue entitled 'Essential role of DHEA'.

ODM-201: a new-generation androgen receptor inhibitor in castration-resistant prostate cancer

Androgen deprivation therapy is the standard of care for patients with advanced hormone-sensitive prostate cancer. Despite an initial response, most patients progress to castration-resistant prostate cancer (CRPC). The realization that CRPC remains driven by androgen receptor (AR) signaling has formed the basis for a new generation of agents targeting the AR axis. Two of these agents, abiraterone acetate and enzalutamide, have been shown to prolong overall survival in patients with CRPC. Several other AR inhibitors are currently in development for the treatment of CRPC. The present article reviews ODM-201, a new-generation AR inhibitor with a unique molecular structure, in the treatment of CRPC. The design of an ongoing Phase III trial (ARAMIS) of ODM-201 in men with non-metastatic CRPC is also discussed, at a disease stage for which there is currently no approved treatment.

Docetaxel rechallenge after an initial good response in patients with metastatic castration-resistant prostate cancer

OBJECTIVE

To evaluate the benefit of docetaxel rechallenge in patients with metastatic castration-resistant prostate cancer (mCRPC) relapsing after an initial good response to first-line docetaxel.

PATIENTS AND METHODS

We retrospectively reviewed the records of consecutive patients with mCRPC with a good response to first-line docetaxel [serum prostate specific antigen (PSA) decrease ≥50%; no clinical/radiological progression]. We analysed the impact of management at relapse (docetaxel rechallenge or non-taxane-based therapy) on PSA response, symptomatic response (performance status/pain/analgesic consumption), and overall survival (OS). We used multivariate stepwise logistic regression to analyse potential predictors of a favourable outcome.

RESULTS

We identified 270 good responders to first-line docetaxel. The median progression-free interval (PFI) was 6 months from the last docetaxel dose. At relapse, 223 patients were rechallenged with docetaxel (82.5%) and 47 received non-taxane-based therapy. There was no significant difference in median OS {18.2 [95% confidence interval (CI) 16.1-22.00] and 16.8 [95%CI 13.4-21.5] months, respectively, P = 0.35}. However, good PSA response and symptom relief/stable disease were more frequent on docetaxel rechallenge (40.4% vs 10.6%, P < 0.001 for PSA). A PFI of >6 months and added estramustine predicted a good PSA response and symptomatic response on docetaxel rechallenge but only a PFI of >6 months predicted longer OS. Haemoglobin (<13 g/dL) and pain were associated with reduced OS. Docetaxel rechallenge increased the incidence of grade ≥3 sensory neuropathy, nail disorders and asthenia/fatigue.

CONCLUSIONS

Docetaxel rechallenge is a management option for responders to docetaxel with a PFI of >6 months, but did not prolong survival. Potential benefits should be weighed against the risk of cumulative toxicity.

Treatment sequencing in metastatic castrate-resistant prostate cancer

Six different treatments have demonstrated improved survival in phase III trials targeted to patients with metastatic castration-resistant prostate cancer (mCRPC). Front-line therapeutic options for mCRPC include docetaxel, sipuleucel-T, abiraterone and radium-223. Post-docetaxel options include cabazitaxel, abiraterone, enzalutamide and radium-223. Despite much progress in recent years, much is yet unknown and debates occur over optimal treatment choices and sequences. None of the new agents have been compared to one another, thus physicians in practice today must make choices based on non-randomized comparisons, toxicity considerations and various assumptions. Abiraterone is now moving into the front line mCRPC space given recent regulatory approvals and enzalutamide will follow soon. Both of the hormonal agents have less toxicity when compared to chemotherapeutic options and both of these hormonal agents are expected to be used in a considerable number of mCRPC patients in the years ahead. Little data are available for the post-abiraterone or post-enzalutamide setting. In this review the currently available sequencing data are summarized and interpreted. It is now clear that cross resistance is a potential issue between various treatments, especially those agents that target the androgen axis. This review highlights the need for additional studies to optimize the current treatments for these patients.

Chemotherapy and its evolving role in the management of advanced prostate cancer

Advanced prostate cancer has been recognized as being responsive to androgen deprivation since the 1940s when Charles Huggins first described the role of surgical castration in managing these patients. However, androgen deprivation only results in transient disease control for the vast majority of men, with those progressing in spite of castrate testosterone levels labeled as having castrate-resistant prostate cancer (CRPC). Until 2004, the therapeutic arena for these patients had remained stagnant, with no agent having shown a survival gain in the CRPC setting. Two landmark publications changed the prostate cancer treatment landscape by providing ‘level-1 evidence’ that docetaxel-based chemotherapy led to prolongation in overall survival (OS). This was followed by the approval of cabazitaxel in 2010 on the basis of Phase III data demonstrating its efficacy in patients pretreated with docetaxel. More recently, a number of next-generation androgen-directed agents (e.g. abiraterone and enzalutamide) have also been shown to lead to a survival benefit in men with CRPC. With so many new treatment options available, a number of questions remain. These include: how to best sequence chemotherapy with these newer hormonal agents, the clinical implication of cross-resistance between taxanes and androgen-directed agents and which subsets of patients may benefit most from early use of chemotherapy. This review will provide an overview of the evolving role of chemotherapy in the management of advanced prostate cancer in the current era.

Further analysis of PREVAIL: enzalutamide use in chemotherapy-naïve men with metastatic castration-resistant prostate cancer

PREVAIL was a phase III multinational, double-blind, placebo-controlled trial that enrolled chemotherapy-naïve men with metastatic castration-resistant prostate cancer (mCRPC), which showed remarkable improvement in co-primary endpoints with an overall 81% reduction in the risk of radiographic progression, as well as 29% reduction in the risk of death in favor of the enzalutamide arm over placebo. All secondary endpoints including time to subsequent chemotherapy initiation and prostate specific antigen (PSA) progression were in favor of the enzalutamide arm. The results of PREVAIL shows the utility of enzalutamide that would likely soon expand the indication to asymptomatic or minimally symptomatic men with mCRPC not previously treated with chemotherapy.

A retrospective, Canadian multi-center study examining the impact of prior response to abiraterone acetate on efficacy of docetaxel in metastatic castration-resistant prostate cancer

BACKGROUND

Questions about optimal sequencing of systemic therapy in metastatic castration-resistant prostate cancer (mCRPC) and whether cross-resistance occurs between different drugs remain largely unanswered. Previous studies have produced conflicting data on the activity of docetaxel in patients who did not attain a prostate-specific antigen (PSA) response to abiraterone acetate (abiraterone). We investigated whether the biochemical response to abiraterone is associated with efficacy of subsequent docetaxel therapy.

METHODS

mCRPC patients treated with docetaxel after abiraterone were retrospectively identified at three Canadian institutions. Patients who had also received docetaxel prior to abiraterone were termed "docetaxel-experienced," while those not treated with docetaxel prior to abiraterone were termed "docetaxel-naïve." Treatment outcomes on docetaxel were stratified by prior response to abiraterone and compared using χ(2) -square test for confirmed PSA response rate (≥ 50% decline from baseline maintained for ≥ 3 weeks) and the log-rank method for progression-free survival (PFS) and overall survival (OS).

RESULTS

Eighty-six patients were treated with abiraterone, of whom 49 were docetaxel-experienced and 37 were docetaxel-naïve. Prior PSA response to abiraterone was no decline, <50% decline and ≥ 50% decline in 37%, 26%, and 37% of patients respectively. The overall PSA response rate to docetaxel was 34.9%, median PFS was 4.0 months and median OS was 11.66 months. Notably, no differences were seen in confirmed PSA response rates (38% vs. 36% vs. 31%, P = 0.86), median PFS (4.04 months vs. 3.94 months vs. 4.24 months, P = 0.43) and median OS (11.86 months vs. 15.38 months vs. 11.00 months, P = 0.56) on docetaxel for patients with no PSA decline, <50% decline and ≥ 50% decline on abiraterone respectively. Importantly, PSA response rates to docetaxel were comparable in the docetaxel-experienced and docetaxel-naïve cohorts and were not linked to prior response to abiraterone in either group.

CONCLUSION

Activity of docetaxel was not associated with the biochemical response to prior abiraterone therapy. These data suggest that prior response to abiraterone should not influence decisions on subsequent use of docetaxel in mCRPC.

Advances in systemic therapies for metastatic castration-resistant prostate cancer

ABSTRACT 

The landscape of treatment for metastatic castration-resistant prostate cancer has rapidly evolved during the last 5 years alone. In this review, standard therapies as well as recent advances in the systemic treatment for prostate cancer are explored. Pivotal trial data are summarized with emphasis on indications for various anti-androgen drugs, androgen-biosynthesis inhibitors, chemotherapy, immunotherapy and bone-targeted agents. The clinical, biochemical and radiographic outcomes for men with metastatic castration-resistant prostate cancer are improving with the establishment of several promising novel agents.

Cytotoxic chemotherapy in the contemporary management of metastatic castration-resistant prostate cancer (mCRPC)

For several years, docetaxel was the only treatment shown to improve survival of patients with metastatic castration-resistant prostate cancer (mCRPC). There are now several novel agents available, although chemotherapy with docetaxel and cabazitaxel continues to play an important role. However, the increasing number of available agents will inevitably affect the timing of chemotherapy and therefore it may be important to offer this approach before declining performance status renders patients ineligible for chemotherapy. Patient selection is also important to optimise treatment benefit. The role of predictive biomarkers has assumed greater importance due to the development of multiple agents and resistance to available agents. In addition, the optimal sequence of treatments remains undefined and requires further study in order to maximize long-term outcomes. We provide an overview of the clinical data supporting the role of chemotherapy in the treatment of mCRPC and the emerging role in metastatic castration-sensitive prostate cancer. We review the key issues in the management of patients including selection of patients for chemotherapy, when to start chemotherapy, and how best to sequence treatments to maximise outcomes. In addition, we briefly summarise the promising new chemotherapeutic agents in development in the context of emerging therapies.

SEOM clinical guidelines for the treatment of metastatic prostate cancer

Androgen deprivation treatment is the current standard first-line treatment for metastatic prostate cancer. For several years, docetaxel was the only treatment with a proven survival benefit for castration-resistant prostate cancer (CRPC). Since docetaxel became standard of care for men with symptomatic metastatic castration-resistant prostate cancer (CRPC), three treatment virtual spaces, for treatment and drug development in CPRC, have emerged: pre-docetaxel, docetaxel combinations and post-docetaxel. Sipuleucel-T, cabazitaxel, abiraterone, enzalutamide and radium-223 have been approved in the pre- or post-docetaxel setting in metastatic CRPC during the last few years. Patients are now living longer and experiencing better quality of life. Strategies for patient selection and treatment sequencing are therefore urgently required.

Novel anti-androgen receptor signaling agents: Understanding the mechanisms of resistance

Prostate cancer remains an intractable threat to the lives of men worldwide. Although deaths from prostate cancer (PCa) in the United States have declined in recent years, in other parts of the world Pca mortality is increasing. The introduction of 2nd generation anti-androgen receptor agents into the therapeutic armamentarium for metastatic castration-resistant prostate cancer (mCRPC) has resulted in modestly increased survival advantages as demonstrated by initial clinical trials. However, analysis of the molecular pathways affected by these agents may lead to new insight into mechanisms of resistance that drive mCRPC, including proliferation and survival signaling pathways that are derepressed by maximum repression of androgen signaling. Combination therapies that involve anti-AR signaling agents together with agents that target these pathways establish a paradigm for the development of more effective treatment of mCRPC. In this review, we briefly summarize the current clinical trial literature with regard to novel anti-AR signaling agents such as abiraterone acetate and enzalutamide. We discuss observational data that point to mechanisms of resistance that emerged from these studies. We further present and discuss recent experimental studies that address the mechanisms of resistance to these treatments. Finally, we discuss novel and rational therapeutic approaches, including combination therapy, for patients with mCRPC.