The role of abiraterone acetate in the management of prostate cancer: a critical analysis of the literature

Abiraterone Acetate Versus Enzalutamide Against Chemo-Naïve Castration-Resistant Prostate Cancer With Full-Dose Induction

Purpose We recently released the multi-institutional real-world analysis about the difference in survival outcomes between abiraterone acetate and enzalutamide against chemo-naïve castration-resistant prostate cancer (CRPC) in a first-line setting. Although reduced dose induction cases were included in that analysis, induction dose reduction might correlate with reduced efficacy. In this study, we analyzed full-dose induction subgroups from our overall cohort and investigated the true difference in efficacy between these agents. Methods A total of 220 chemotherapy-naïve CRPC cases treated with full-dose induction of first-line androgen receptor signaling inhibitor (ARSI) were analyzed. Outcome measures were prostate-specific antigen (PSA) response, PSA progression-free survival (PSA-PFS), treatment failure-free survival (TFF), cancer-specific survival (CSS), and overall survival (OS). Results Abiraterone acetate and enzalutamide were administered to 58 and 162 patients, respectively. The median PSA response rate (-65.4% (A) and -81.5% (E), p = 0.0252), PSA decline ≥ 90% (22.4% (A) and 37.0% (E), p = 0.0478), PSA-PFS (median four months (A) and seven months (E), p = 0.00833), TFF (median six months (A) and 15 months (E), p<0.0001), CSS (median 45 months (A) and not reached (E), p < 0.0001), and OS (median 34 months (A) and 80 months (E), p<0.001) were significantly better in the E group. Conclusion This study showed that PSA response, PSA-PFS, TTF, CSS, and OS were better with first-line enzalutamide administration. Direct inhibition of androgen receptor signaling by enzalutamide is associated with better clinical outcomes in the full-dose induction cohort.

Survival outcome of chemotherapy-naïve castration-resistant prostate cancer treated with new-generation androgen receptor axis-targeted agents in real-world analysis

PURPOSE

The androgen receptor axis-targeted (ARAT) agents abiraterone and enzalutamide have been introduced against castration-resistant prostate cancer (CRPC). However, determining which of these agents should be used first is a clinical challenge. Therefore, in this study, we compared the efficacy of first-line abiraterone and enzalutamide treatments in chemotherapy-naïve patients with CRPC.

METHODS

A total of 242 chemotherapy-naïve CRPC cases treated with first-line ARAT were analyzed. Outcome measures were PSA response, PSA progression-free survival (PSA-PFS), time to treatment failure (TTF), cancer specific survival (CSS), and overall survival (OS).

RESULTS

Abiraterone (A) and enzalutamide (E) were administered to 61 and 181 patients, respectively. The median PSA response rate (- 65.4% [A] and - 78.8% [E], p = 0.0341), PSA decline ≥ 30% (55.7% [A] and 72.9% [E], p = 0.0183), PSA-PFS (median 4 months [A] and 8 months [E], p = 0.0126), TTF (median 6 months [A] and 14 months [E], p < 0.0001), CSS (median 45 months [A] and not reached [E], p < 0.0001), and OS (median 28 months [A] and 80 months [E], p < 0.001) were significantly better in the enzalutamide group. In the multivariate analyses for CSS and OS, ALP (p = 0.00376) and ARAT (p < 0.001) (CSS), evidence of metastasis (p = 0.0467), Hb (p = 0.00205), and ARAT (p = 0.00514) (OS) were significant factors, respectively.

CONCLUSION

This study showed that PSA response, PSA-PFS, TTF, CSS, and OS were better with first-line enzalutamide administration. Direct inhibition of androgen receptor signaling by enzalutamide is associated with better clinical outcomes.

Synthesis and clinical application of small-molecule drugs approved to treat prostatic cancer

Prostate cancer is a prevalent form of cancer that primarily affects men, with a high incidence and mortality rate. It is the second most common cancer among males, following lung cancer. Typically occurring in individuals aged 50 and above, this malignant tumor originates from abnormal cells in the prostate tissue. If left untreated, it can spread to nearby tissues, lymph nodes, and even bones. Current treatment methods include surgery, radiotherapy, and chemotherapy. However, these treatments have certain limitations and side effects. Therefore, researching and developing new small-molecule drugs to treat prostate cancer is of great significance. In recent years, many small-molecule drugs have been proven to have therapeutic effects on prostate cancer. The purpose of this review is to give a comprehensive look at the clinical uses and synthetic methods of various significant small-molecule drugs that have been approved to treat prostate cancer, to facilitate the development of more powerful and innovative drugs for the effective control of prostate cancer.

The Discovery of BMS-737 as a Potent, CYP17 Lyase-Selective Inhibitor for the Treatment of Castration-Resistant Prostate Cancer

We report herein, the discovery of BMS-737 (compound 33) as a potent, non-steroidal, reversible small molecule inhibitor demonstrating 11-fold selectivity for CYP17 lyase over CYP17 hydroxylase, as well as a clean xenobiotic CYP profile for the treatment of castration-resistant prostate cancer (CRPC). Extensive SAR studies on the initial lead 1 at three different regions of the molecule resulted in the identification of BMS-737, which demonstrated a robust 83% lowering of testosterone without any significant perturbation of the mineralocorticoid and glucocorticoid levels in cynomologous monkeys in a 1-day PK/PD study.

Resistance to prostate cancer treatments

A review of the current treatment options for prostate cancer and the formation of resistance to these regimens has been compiled including primary, acquired, and cross-resistance. The diversification of the pathways involved and the escape routes the tumor is utilizing have been addressed. Whereas early stages of tumor can be cured, there is no treatment available after a point of no return has been reached, leaving palliative treatment as the only option. The major reasons for this outcome are the heterogeneity of tumors, both inter- and intra-individually and the nearly endless number of escape routes, which the tumor can select to overcome the effects of treatment. This means that more focus should be applied to the individualization of both diagnosis and therapy of prostate cancer. In addition to current treatment options, novel drugs and ongoing clinical trials have been addressed in this review.

Drug resistance in metastatic castration-resistant prostate cancer: an update on the status quo

Prostate cancer (PCa) is a leading cause of cancer-related morbidity and mortality in men globally. Despite improvements in the diagnosis and treatment of PCa, a significant proportion of patients with high-risk localized disease and all patients with advanced disease at diagnosis will experience progression to metastatic castration-resistant prostate cancer (mCRPC). Multiple drugs are now approved as the standard of care treatments for patients with mCRPC that have been shown to prolong survival. Although the majority of patients will respond initially, primary and secondary resistance to these therapies make mCRPC an incurable disease. Several molecular mechanisms underlie the development of mCRPC, with the androgen receptor (AR) axis being the main driver as well as the key drug target. Understanding resistance mechanisms is crucial for discovering novel therapeutic strategies to delay or reverse the progression of the disease. In this review, we address the diverse mechanisms of drug resistance in mCRPC. In addition, we shed light on emerging targeted therapies currently being tested in clinical trials with promising potential to overcome mCRPC-drug resistance.

Resistance to Antiandrogens in Prostate Cancer: Is It Inevitable, Intrinsic or Induced?

Increasingly sophisticated therapies for chemical castration dominate first-line treatments for locally advanced prostate cancer. However, androgen deprivation therapy (ADT) offers little prospect of a cure, as resistant tumors emerge rather rapidly, normally within 30 months. Cells have multiple mechanisms of resistance to even the most sophisticated drug regimes, and both tumor cell heterogeneity in prostate cancer and the multiple salvage pathways result in castration-resistant disease related genetically to the original hormone-naive cancer. The timing and mechanisms of cell death after ADT for prostate cancer are not well understood, and off-target effects after long-term ADT due to functional extra-prostatic expression of the androgen receptor protein are now increasingly being recorded. Our knowledge of how these widely used treatments fail at a biological level in patients is deficient. In this review, I will discuss whether there are pre-existing drug-resistant cells in a tumor mass, or whether resistance is induced/selected by the ADT. Equally, what is the cell of origin of this resistance, and does it differ from the treatment-naïve tumor cells by differentiation or dedifferentiation? Conflicting evidence also emerges from studies in the range of biological systems and species employed to answer this key question. It is only by improving our understanding of this aspect of treatment and not simply devising another new means of androgen inhibition that we can improve patient outcomes.

The Androgen Receptor in Prostate Cancer: Effect of Structure, Ligands and Spliced Variants on Therapy

The androgen receptor (AR) plays a predominant role in prostate cancer (PCa) pathology. It consists of an N-terminal domain (NTD), a DNA-binding domain (DBD), a hinge region (HR), and a ligand-binding domain (LBD) that binds androgens, including testosterone (T) and dihydrotestosterone (DHT). Ligand binding at the LBD promotes AR dimerization and translocation to the nucleus where the DBD binds target DNA. In PCa, AR signaling is perturbed by excessive androgen synthesis, AR amplification, mutation, or the formation of AR alternatively spliced variants (AR-V) that lack the LBD. Current therapies for advanced PCa include androgen synthesis inhibitors that suppress T and/or DHT synthesis, and AR inhibitors that prevent ligand binding at the LBD. However, AR mutations and AR-Vs render LBD-specific therapeutics ineffective. The DBD and NTD are novel targets for inhibition as both perform necessary roles in AR transcriptional activity and are less susceptible to AR alternative splicing compared to the LBD. DBD and NTD inhibition can potentially extend patient survival, improve quality of life, and overcome predominant mechanisms of resistance to current therapies. This review discusses various small molecule and other inhibitors developed against the DBD and NTD—and the current state of the available compounds in clinical development.

Exosomes are the Driving Force in Preparing the Soil for the Metastatic Seeds: Lessons from the Prostate Cancer

Exosomes are nano-membrane vesicles that various cell types secrete during physiological and pathophysiological conditions. By shuttling bioactive molecules such as nucleic acids, proteins, and lipids to target cells, exosomes serve as key regulators for multiple cellular processes, including cancer metastasis. Recently, microvesicles have emerged as a challenge in the treatment of prostate cancer (PCa), encountered either when the number of vesicles increases or when the vesicles move into circulation, potentially with an ability to induce drug resistance, angiogenesis, and metastasis. Notably, the exosomal cargo can induce the desmoplastic response of PCa-associated cells in a tumor microenvironment (TME) to promote PCa metastasis. However, the crosstalk between PCa-derived exosomes and the TME remains only partially understood. In this review, we provide new insights into the metabolic and molecular signatures of PCa-associated exosomes in reprogramming the TME, and the subsequent promotion of aggressive phenotypes of PCa cells. Elucidating the molecular mechanisms of TME reprogramming by exosomes draws more practical and universal conclusions for the development of new therapeutic interventions when considering TME in the treatment of PCa patients.

Serious Hypokalemia Associated with Abiraterone Acetate in Patients with Castration-Resistant Prostate Cancer

Introduction

The treatment strategy for castration-resistant prostate cancer (CRPC) has changed with the approval of several new agents. In 2011, abiraterone acetate was approved for the treatment of metastatic CRPC; however abiraterone is known to cause mineralocorticoid excess syndrome characterized by hypokalemia, fluid retention, and hypertension. We experienced two cases of grade 4 hypokalemia associated with abiraterone treatment.

Case Presentation

Case 1: a 71-year-old male with metastatic CRPC presented with convulsive seizures two weeks after receiving abiraterone plus prednisone. The serum potassium level was 2.1mEq/l. We determined that convulsive seizure was caused by hypokalemia associated with abiraterone. Case 2: a 68-year-old male with metastatic CRPC presented with severe lethargy one month after receiving abiraterone plus prednisone. The serum potassium level was 1.7mEq/l and we concluded that severe lethargy was caused by hypokalemia associated with abiraterone. They were treated with potassium supplementation and increased prednisone following withdrawal of abiraterone.

Discussion

The two patients had been on glucocorticoid therapy before abiraterone therapy. Prolonged administration of exogenous glucocorticoid can lead adrenocortical insufficiency and consequently reduce endogenous glucocorticoid production. This situation may increase the risk of abiraterone-induced mineralocorticoid excess. To reduce the risk of abiraterone-induced hypokalemia, evaluation of adrenocortical insufficiency is required.

Amiloride Is Effective in the Management of Abiraterone-Induced Mineralocorticoid Excess Syndrome without Interfering with Its Antineoplastic Activity

Background: The administration of abiraterone acetate (abiraterone) leads to an adrenocorticotropic hormone (ACTH)-driven increase in mineralocorticoid hormones, requiring glucocorticoid supplementation that may stimulate the growth of prostate cancer (PCa). Amiloride is a drug that selectively reduces the aldosterone-sensitive Na+/K+ exchange and could be effective in the management of mineralocorticoid excess syndrome (MCES). Methods: The efficacy of amiloride + hydrochlorothiazide (HCT) in the clinical management of abiraterone-induced MCES was assessed in 5 consecutive patients with castration-resistant PCa (CRPC). Then, using the in vitro experimental model of PCa cell lines, the possible effects of drugs usually used in the clinical management of CRPC patients on PCa cell viability were investigated. Results: Amiloride/HCT led to a complete disappearance of all clinical and biochemical signs of abiraterone-induced MCES in the 5 treated patients. The in vitro study showed that abiraterone treatment significantly decreased cell viability of both androgen receptor (AR)-expressing VCaP (vertebral-cancer of the prostate) and LNCaP (lymph node carcinoma of the prostate) cells, with no effect on AR-negative PC-3 cells. Prednisolone, spironolactone, and eplerenone increased LNCaP cell viability, while amiloride reduced it. The non-steroid aldosterone antagonist PF-03882845 did not modify PCa cell viability. Conclusions: The combination of amiloride/HCT was effective in the management of abiraterone-induced MCES. Amiloride did not negatively interfere with the abiraterone inhibition of PCa cell viability in vitro.

The Emergence of Precision Urologic Oncology: A Collaborative Review on Biomarker-driven Therapeutics

CONTEXT

Biomarker-driven cancer therapy, also referred to as precision oncology, has received increasing attention for its promise of improving patient outcomes by defining subsets of patients more likely to respond to various therapies.

OBJECTIVE

In this collaborative review article, we examine recent literature regarding biomarker-driven therapeutics in urologic oncology, to better define the state of the field, explore the current evidence supporting utility of this approach, and gauge potential for the future.

EVIDENCE ACQUISITION

We reviewed relevant literature, with a particular focus on recent studies about targeted therapy, predictors of response, and biomarker development.

EVIDENCE SYNTHESIS

The recent advances in molecular profiling have led to a rapid expansion of potential biomarkers and predictive information for patients with urologic malignancies. Across disease states, distinct molecular subtypes of cancers have been identified, with the potential to inform choices of management strategy. Biomarkers predicting response to standard therapies (such as platinum-based chemotherapy) are emerging. In several malignancies (particularly renal cell carcinoma and castration-resistant prostate cancer), targeted therapy against commonly altered signaling pathways has emerged as standard of care. Finally, targeted therapy against alterations present in rare patients (less than 2%) across diseases has the potential to drastically alter patterns of care and choices of therapeutic options.

CONCLUSIONS

Precision medicine has the highest potential to impact the care of patients. Prospective studies in the setting of clinical trials and standard of care therapy will help define reliable predictive biomarkers and new therapeutic targets leading to real improvement in patient outcomes.

PATIENT SUMMARY

Precision oncology uses molecular information (DNA and RNA) from the individual and the tumor to match the right patient with the right treatment. Tremendous strides have been made in defining the molecular underpinnings of urologic malignancies and understanding how these predict response to treatment-this represents the future of urologic oncology.

An Update on Triptorelin: Current Thinking on Androgen Deprivation Therapy for Prostate Cancer

Androgen deprivation therapy (ADT) is the mainstay palliative treatment for men with locally advanced and metastatic prostate cancer, and aims to reduce testosterone to levels obtained by surgical castration. Use of gonadotropin-releasing hormone (GnRH) agonists predominates among the ADT options. The GnRH agonist, triptorelin is a first-line hormonal therapy that has demonstrated efficacy and safety in clinical trials of patients with locally advanced non-metastatic or metastatic disease. Sustained-release 1-, 3- and 6-month formulations of triptorelin, administered intramuscularly or subcutaneously, have been developed to provide improved flexibility and convenience for the patient. Head-to-head studies of GnRH agonists are lacking in the field of prostate cancer. Despite the inevitable progression to castration-resistant prostate cancer (CRPC) in most patients receiving ADT, monitoring of testosterone levels needs to improve in routine practice and physicians should not overlook the benefits of continued ADT in their patients when introducing one of the various new treatment options for CRPC. For improved survival outcomes, there remains a need to tailor ADT treatment regimens, novel hormonal agents and chemotherapy according to the individual patient with advanced prostate cancer.

Prognostic Role of Neutrophil-to-Lymphocyte Ratio in Prostate Cancer: A Systematic Review and Meta-analysis

Inflammation is increasingly reported to be associated with the prognosis of patients with cancers. And the prognostic role of neutrophil-to-lymphocyte ratio (NLR) in patients with prostate cancer (PCa) remains inconsistent. Therefore, we conducted this systematic review and meta-analysis to obtain a more reliable assessment of prognostic significance of NLR in PCa.A comprehensive literature research regarding the association of NLR and prognosis of PCa was performed through PubMed, Embase, Cochrane Central, and Web of Science. The hazard ratios (HRs) and its 95% confidence intervals (CIs) for overall survival (OS), progression-free survival, or recurrence-free survival were extracted and pooled using fix-effects model or random-effects model.A total of 14 studies that met our criterion were included in this meta-analysis. Our pooled results demonstrated that elevated NLR was not significantly associated with the poor OS (HR = 1.45; 95% CI 0.77-2.71; P = 0.248) or recurrence-free survival (HR = 1.34; 95% CI 0.89-2.02; P = 0.155) of patients with localized PCa. Although elevated NLR predicted poorer OS (HR = 1.57; 95% CI 1.41-1.74; P < 0.001) and progression-free survival (HR = 1.97; 95% CI 1.28-3.04; P = 0.002) of patients with metastatic castration resistant prostate cancer (mCRPC).Elevated NLR is a strong indicator of poorer prognosis of patients with mCRPC, whereas the NLR is not significantly associated with prognosis of patients with localized PCa. Therefore, NLR could be used in patients with mCRPC for risk stratification and decision making of individual treatment.

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.

Androgen deprivation therapy in castrate-resistant prostate cancer: how important is GnRH agonist backbone therapy?

BACKGROUND

A growing number of treatment options exist to treat metastatic castrate-resistant prostate cancer (mCRPC), and with these newer options, many questions about optimising treatment remain unanswered. One recommendation that may potentially be overlooked by practitioners is that androgen deprivation therapy (ADT) should be maintained when CRPC develops and when treatment with any of the newer agents is initiated.

AIM

However, to emphasise this recommendation, it is valuable to interrogate the evidence for maintaining ADT in different clinical situations.

OUTCOME

This statement, reflecting the views of the authors, provides a discussion of this evidence and the rationale behind the recommendation that ADT should be continued in CRPC.

Determination of 17α-hydroxylase-C17,20-lyase (P45017α) enzyme activities and their inhibition by selected steroidal picolyl and picolinylidene compounds

17α-hydroxylase-C17,20-lyase (P45017α) is a key regulator enzyme of the steroid hormone biosynthesis in both the adrenals and the testes. Inhibition of this enzyme can block androgen synthesis in an early step, and may thereby be useful in the treatment of several androgen-dependent diseases. We developed radio-substrate in vitro incubation methods for the determination of the distinct 17α-hydroxylase and C17,20-lyase activities of the enzyme using rat testicular homogenate as enzyme source. With this method we have studied the inhibiting activity of selected steroidal picolyl and picolinylidene compounds. Tests revealed a substantial inhibitory action of the 17-picolinyliden-androst-4-en-3-one compound.

Association of pretreatment neutrophil-to-lymphocyte ratio (NLR) and overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with first-line docetaxel

OBJECTIVE

To determine whether the pretreatment neutrophil-to-lymphocyte ratio (NLR), a measure of systemic inflammatory response, is associated with overall survival (OS) in men receiving chemotherapy with docetaxel for metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Records from 238 consecutive patients who were treated with first-line docetaxel-containing chemotherapy for mCRPC at a single high-volume centre from 1998 to 2010 (and who had adequate information to enable calculation of NLR) were reviewed. Univariable and multivariable Cox regression models were used to predict OS after chemotherapy initiation.

RESULTS

In univariable analyses, the NLR as a discrete variable (optimal threshold 3.0) was significantly associated with OS (P = 0.001). In multivariable analyses, a lower NLR (≤3.0) was associated with lower risk of all-cause mortality (P = 0.002). In Kaplan-Meier analysis, the median OS was higher (18.3 vs 14.4 months) in patients that did not have an elevated NLR than in those with an elevated NLR (log-rank; P < 0.001).

CONCLUSIONS

Men who were treated with first-line docetaxel for mCRPC who had a low pretreatment NLR (≤3.0) had significantly longer OS. NLR may be a potentially useful clinical marker of systemic inflammatory response in predicting OS in men with mCRPC who receive docetaxel and may be helpful to stratify patients for clinical trials. These findings derived from a retrospective analysis need to be validated in larger populations in prospective studies, and in the context of different therapies.

Steroidal 5α-reductase and 17α-hydroxylase/17,20-lyase (CYP17) inhibitors useful in the treatment of prostatic diseases

The role of steroidal inhibitors of androgen biosynthesis as potential weapons in the treatment of prostatic diseases, such as benign prostatic hyperplasia and prostatic cancer will be reviewed. Two enzymes have been targeted in the development of inhibitors that potentially could be useful in the management of such conditions. 5α-Reductase is primarily of interest in benign prostatic disease, though some role in the chemoprevention of prostatic carcinoma have been considered, whereas the 17α-hydroxylase/17,20-lyase (CYP17) enzyme is of interest in the treatment of malignant disease. An overview of the main achievements obtained during the past years will be presented, however special focus will be made on steroidal molecules that reached clinical trials or have been commercially launched. Relevant examples of such drugs are finasteride, dutasteride, abiraterone acetate and galeterone (TOK-001, formerly known as VN/124-1). This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Clinical Evaluation of Abiraterone in the Treatment of Metastatic Prostate Cancer

Treatment of castration-resistant prostate cancer remains an area of unmet medical need. Evidence suggests that this entity continues to be driven by androgens and androgen receptor (AR) signaling. Abiraterone acetate, a pregnenolone derivative, is an oral selective and irreversible inhibitor of the key steroidogenic enzyme CYP17. It possesses dual 17-α hydroxylase and C17,20-lyase blocking activity, the result of which is decreased gonadal and extra-gonadal androgen synthesis. Abiraterone was first approved by the US Food and Drug Administration (FDA) in 2011 following the demonstration of superior survival compared with placebo in the post-docetaxel population. Since that time, more evidence has been generated from preclinical studies and clinical trials which have considerably enhanced our understanding of this complex disease. In this paper, we review the development of abiraterone acetate, its pharmacological characteristics, and its effects on the androgen-AR signaling axis, along with the combined experience from clinical trials. We also discuss some of the ongoing trials using this agent, as well as potential mechanisms of abiraterone resistance, novel bio-marker development, and future directions using AR-directed therapies.

Enzalutamide in castration-resistant prostate cancer patients progressing after docetaxel and abiraterone

BACKGROUND

Abiraterone, an androgen synthesis inhibitor, has been successfully used in the treatment of castration-resistant prostate cancer (CRPC) for 2 yr. Enzalutamide is a second-generation nonsteroidal antiandrogen that has recently been approved for the same indication.

OBJECTIVE

This is the first study to evaluate the effectiveness of enzalutamide after failure of abiraterone.

DESIGN, SETTING, AND PARTICIPANTS

Thirty-five patients were identified as having received sequential therapy with abiraterone followed by enzalutamide. All patients had undergone prior docetaxel chemotherapy, and no patient had received ketoconazole.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Posttreatment changes in prostate-specific antigen (PSA) were used to determine the activity of enzalutamide in patients who had received prior abiraterone.

RESULTS AND LIMITATIONS

The median duration of abiraterone treatment was 9.0 mo (range: 2.0-19.0 mo). Of the 35 patients, 16 (45.7%) achieved a >50% decline in PSA, and 14 (40%) had a rising PSA as the best response. The median duration of subsequent enzalutamide treatment was 4.9 mo (Kaplan-Meier estimate; 95% confidence interval [CI], 2.4-7.4). Seven of 16 CRPC patients who were initially abiraterone-sensitive (43.8%) and 3 of 19 CRPC patients who were initially abiraterone-insensitive (15.8%) showed a >50% PSA decline while taking enzalutamide. Of the 35 patients, 17 (48.6%) were primarily enzalutamide-resistant and showed a rising PSA as the best response. Median time to progression was 4.0 mo (95% CI, 2.0-6.0) for 18 of 35 patients with at least one declining PSA value while taking enzalutamide (51.4%). Of the 17 patients who were assessable radiologically, only 1 (2.9%) attained a confirmed partial response. Small sample size was the major limitation.

CONCLUSIONS

Enzalutamide treatment achieved only a modest response rate in patients progressing after abiraterone. Although cross-resistance between abiraterone and enzalutamide was a common phenomenon, it was not inevitable, and a small but significant number of patients showed significant benefit from sequential treatment.

Strategies for managing ACTH dependent mineralocorticoid excess induced by abiraterone

BACKGROUND

Abiraterone strongly inhibits androgen synthesis but may lead to an increase in mineralocorticoid hormones that may impair its long term tolerability in patients with prostate cancer. How to implement available therapies in the management and prevention of these potential side effects is a matter of current clinical research.

METHODS

The acute and long term consequences of mineralocorticoid excess and the effects of available treatments have been reviewed. Prospective studies in which abiraterone was employed were identified to assess the frequency and severity of the mineralocorticoid excess syndrome and the efficacy of ameliorating therapeutic approaches.

RESULTS

Glucocorticoids to inhibit the ACTH increase that drives mineralocorticoid synthesis and mineralocorticoid receptor (MR) antagonists can be used in the management of the abiraterone-induced mineralocorticoid excess syndrome. Phase I and II trials of abiraterone without additional therapies revealed that mineralocorticoid excess symptoms occur in the majority of patients. Eplerenone, a specific MR antagonist, seems to be effective but it does not control the mineralocorticoid excess. Glucorticoid supplementation to control ACTH drive is therefore needed. In several randomized trials the addition of prednisone (10mg daily) to abiraterone was not able to prevent mineralocorticoid excess syndrome in many cases and thus cannot be considered the gold standard.

CONCLUSION

At present, the best conceivable treatment for managing the abiraterone-induced mineralocorticoid excess consists of the administration of glucocorticoid replacement at the lowest effective dose ± MR antagonists and salt deprivation. The drug doses should be modulated by monitoring blood pressure, fluid retention and potassium levels during therapy.

[Novel agents for the therapy of castration-resistant prostate cancer: overview of pivotal studies and new strategies to come]

OBJECTIVE

Recently, new agents have been developed in the treatment of prostate cancer. Our aim was to review phase III studies that involved novel agents in the treatment of castration resistant prostate cancer.

METHODS

PubMed databases were searched for original articles published with the search terms: prostate cancer, castration resistant, metastatic, targeted therapy, biologic agents, immunotherapy and clinical trials. Proceedings from 2008 of conferences of the American Society of Clinical Oncology, American Urological Association, and the European Association of Urology were also searched. We included phase III studies that involved: abiraterone, MDV 3100, cabazitaxel, sipuleucel-T, radium-223, and denosumab.

RESULTS

Abiraterone and MDV 3100 are two new hormotherapies that showed an increased overall survival of 15 and 18 months respectively before after docetaxel based chemotherapy in randomized trials. Cabazitaxel became the standard second line chemotherapy after docetaxel. Sipuleucel-T has emerged as the first approved vaccine in prostate cancer. It showed a 22 % reduction of mortality and a prolonged survival time of 4.1 months compared to placebo. A radium-223 based metabolic radiotherapy has showed a better overall survival, delayed and reduced skeletal-related events in placebo controlled randomized trials. Denosumab also delayed the first skeletal-related event in a zoledronic acid controlled trial (20.7 versus 17.1 months, P=0.0002). Moreover, Denosumab delays bone metastases by 4.1 months compared to placebo.

CONCLUSION

The novel agents that emerged in the treatment of prostate cancer showed an efficacy in placebo controlled trials. They added new tools in the armamentarium of therapies of castration resistant prostate cancer.

High tissue density of FOXP3+ T cells is associated with clinical outcome in prostate cancer

Cell-mediated immunity may impact prostate cancer progression and has great therapeutic potential. Here, we investigated the clinical significance of the numeric density of regulatory T cells (Tregs) in prostate cancer as the presence of such cells in the tumour microenvironment has been linked to clinical outcome in other tumour entities. We detected Tregs by FOXP3 immunohistochemistry in 88.8% of 2002 prostate cancer specimens in tissue microarray format, the largest cohort so far in which Tregs have been quantified. The density of Tregs in tumour tissue was compared with pathological parameters and clinical outcome. The number of Tregs identified per 0.6mm tissue spot ranged from 1 to 10 in normal and 1 to 103 FOXP3+ cells in tumour samples. Prostate-specific antigen (PSA) recurrence-free survival was significantly reduced in patients with higher numbers of Tregs (p=0.0151). Further, a higher number of intratumoural FOXP3+ Tregs was associated with a more advanced tumour stage (p=0.0355) and higher Ki67 labelling index (p<0.0001). The tissue density of Tregs was unrelated to other clinical parameters such as spread to lymph nodes, preoperative PSA level and Gleason score. Our study suggests that the intratumoural presence of regulatory T cells may have substantial functional impact and may confer an adverse clinical course in prostate cancer.

The effect of clinical trial participation versus non-participation on overall survival in men receiving first-line docetaxel-containing chemotherapy for metastatic castration-resistant prostate cancer

What's known on the subject? and What does the study add? Previous studies have reported better outcomes in cancer patients that enrolled in clinical trials, suggesting that trial participation in itself might be beneficial. We investigated the potential positive effect of clinical trial participation on survival outcomes of patients with metastatic castration-resistant prostate cancer who were treated with first-line docetaxel-containing chemotherapy. After accounting for potential baseline inequalities, participation in a clinical trial itself was associated with significantly longer overall survival in these patients.

OBJECTIVE

• To study differences in baseline characteristics and outcomes of patients with metastatic castration-resistant prostate cancer (mCRPC) receiving first-line docetaxel-containing chemotherapy on prospective clinical studies (trial participants) versus those receiving this therapy outside of a clinical study (non-participants).

PATIENTS AND METHODS

• Records from 247 consecutive chemotherapy-naive patients who were treated with docetaxel-containing chemotherapy for mCRPC at a single high-volume centre from 1998 to 2010 were reviewed. • All patients received docetaxel either as clinical trial participants (n= 142; 11 separate studies) or as non-participants (n= 105). • Univariable and multivariable Cox regression models predicted overall survival after chemotherapy initiation.

RESULTS

• There was no significant difference between trial participation and non-participation with respect to patient age, type of primary treatment, tumour grade or clinical stage. • Multivariable analyses showed a significantly lower risk of all-cause mortality (hazard ratio 0.567; P= 0.027) among trial participants vs non-participants.

CONCLUSIONS

• Patients that were treated with docetaxel for mCRPC showed a significantly longer overall survival when enrolled in a clinical trial. • Improved survival in trial participants may reflect the better medical oversight typically seen in patients enrolled in trials, more regimented follow-up schedules, or a positive effect on caregivers' attitudes because of greater contact with medical services. • With the retrospective nature of this analysis and the small study population, prospective studies are needed to validate the present findings and to further investigate the relationship between clinical trial participation and outcomes.

Development and clinical utility of abiraterone acetate as an androgen synthesis inhibitor

In April 2011, abiraterone acetate (AA) was approved by the US Food and Drug Administration (FDA) for the treatment of metastatic castration-resistant prostate cancer (CRPC) after chemotherapy. The development of AA is the direct result of our increased understanding of the intricacies of the androgen receptor (AR) pathway and its natural evolution in prostate cancer cells over the course of treatment. In this paper we review the biology of the AR and how it led to the rational design of AA. We also examine the clinical development of AA, its current use, and questions to be addressed for future development.