Antiandrogen withdrawal in castrate-refractory prostate cancer: a Southwest Oncology Group trial (SWOG 9426)

Androgen Receptor Signaling Inhibitor Withdrawal Syndrome After Castration-resistant Prostate Cancer

Androgen-deprivation therapy is an extremely effective treatment for progressive prostate cancer. Previously, the first-line treatment for progressive prostate cancer was combined androgen blockade (CAB). If the disease progressed to castration-resistant prostate cancer, the administration of androgen receptor signaling inhibitors (ARSIs) was recommended. When elevated serum prostate-specific antigen (PSA) levels are seen during CAB treatment, it is important to suspect antiandrogen withdrawal syndrome (AWS), discontinue CAB, and monitor the changes in the serum PSA levels. If a reduction in the patient's PSA levels is subsequently observed, antiandrogens should be discontinued and the patient should be followed, but if their PSA level rises they should be transitioned to ARSI treatment. Recently, there have been reports of withdrawal syndrome (WS) after ARSI treatment. With the increased use of ARSIs, such as abiraterone acetate, enzalutamide, apalutamide, and dalorutamide, it is necessary to consider ARSI WS when a patient's serum PSA level increases during ARSI treatment. Unnecessary treatment can be avoided if the confirmation of ARSI WS is prioritized. Conversely, if it is not confirmed there is a risk that second-line treatment will be delayed. This is a review of recent studies of ARSI WS. It also discusses future prospects in this field.

Prognostic factors for non‑metastatic castration‑resistant prostate cancer treated with androgen receptor signaling inhibitors

The treatment paradigm for non-metastatic castration-resistant prostate cancer (nmCRPC) has changed in recent years. An observational multicenter study was conducted to evaluate the effectiveness of androgen receptor signaling inhibitors (ARSIs) as a first-line treatment for patients with nmCRPC. The present study included native Japanese patients from four hospitals who received ARSIs as a first-line treatment for nmCRPC. The primary endpoint of the study was to evaluate the efficacy and safety of ARSI in patients with nmCRPC. The secondary endpoint was to develop a novel system to stratify the prognoses of these patients. In total, 160 patients were included in the present study. Within a median follow-up period of 23 months, the median overall survival (OS) was not reached, whereas the median progression-free survival was 26 months. Multivariate Cox regression analyses showed that the time to CRPC, prostate-specific antigen (PSA) level at the initiation of nmCRPC treatment and Geriatric Nutritional Risk Index (GNRI) were independent predictors of OS. The patients for whom information about all three independent OS predictors was available were subsequently divided into three groups as follows: Group 1, 57 patients with negative or one positive independent OS predictor; group 2, 38 patients with two positive independent OS predictors; and group 3, 10 patients with three independent OS predictors. The OS differed significantly among the three groups (P<0.0001). In conclusion, ARSIs as a first-line treatment may be associated with favorable outcomes in Japanese patients with nmCRPC. Time to CRPC, PSA level at the initiation of nmCRPC treatment and GNRI are potential predictors of OS in Japanese patients with nmCRPC who received ARSIs as a first-line treatment.

Bone health and body composition in prostate cancer: Meet-URO and AIOM consensus about prevention and management strategies

BACKGROUND

Prostate cancer (PCa) treatments are associated with a detrimental impact on bone health (BH) and body composition. However, the evidence on these issues is limited and contradictory. This consensus, based on the Delphi method, provides further guidance on BH management in PCa.

MATERIALS AND METHODS

In May 2023, a survey made up of 37 questions and 74 statements was developed by a group of oncologists and endocrinologists with expertise in PCa and BH. In June 2023, 67 selected Italian experts, belonging to the Italian scientific societies Italian Association of Medical Oncology and Italian Network for Research in Urologic-Oncology (Meet-URO), were invited by e-mail to complete it, rating their strength of agreement with each statement on a 5-point scale. An agreement ≥75% defined the statement as accepted.

RESULTS

In non-metastatic hormone-sensitive PCa, the panel agreed that androgen deprivation therapy (ADT) alone implies sufficient fracture risk to warrant antifracture therapy with bone-targeting agents (BTAs) for cancer treatment-induced bone loss (CTIBL) prevention (79%). Therefore, no consensus was reached (48%) for the treatment with BTAs of patients receiving short-term ADT (<6 months). All patients receiving active treatment for metastatic hormone-sensitive PCa (75%), non-metastatic castration-resistant PCa (89%) and metastatic castration-resistant PCa (mCRPC) without bone metastases (84%) should be treated with BTAs at the doses and schedule for CTIBL prevention. All mCRPC patients with bone metastasis should be treated with BTAs to reduce skeletal-related events (94%). In all settings, the panel analyzed the type and timing of treatments and examinations to carry out for BH monitoring. The panel agreed on the higher risk of sarcopenic obesity of these patients and its correlation with bone fragility.

CONCLUSIONS

This consensus highlights areas lacking major agreement, like non-metastatic hormone-sensitive prostate cancer patients undergoing short-term ADT. Evaluation of these issues in prospective clinical trials and identification of early biomarkers of bone loss are particularly urgent.

Improving the identification of high-risk non-metastatic castration-resistant prostate cancer patients in clinical practice

Non-metastatic castration-resistant prostate cancer (nmCRPC) represents a challenging disease state in prostate cancer care. nmCRPC patients with a high risk of progression to metastatic disease who are identified by a prostate-specific antigen doubling time (PSADT) ≤10 months are eligible for treatment with the novel androgen receptor inhibitors (ARIs), shown to delay disease progression and extend survival. However, nmCRPC is often unexploited in clinical practice due to a lack of standardization in the methodology and in the tools used for its identification. In this article, a group of Urology and Oncology specialists with acknowledged expertise in prostate cancer reviews the state of the art in the management of high-risk nmCRPC patients, identifies gaps and unmet needs, and proposes strategies to optimize the identification of this patient subgroup in the clinical practice and improve their health outcomes.

Circulating tumor DNA landscape and prognostic impact of acquired resistance to targeted therapies in cancer patients: a national center for precision medicine (PRISM) study

BACKGROUND

Despite the effectiveness of the various targeted therapies currently approved for solid tumors, acquired resistance remains a persistent problem that limits the ultimate effectiveness of these treatments. Polyclonal resistance to targeted therapy has been described in multiple solid tumors through high-throughput analysis of multiple tumor tissue samples from a single patient. However, biopsies at the time of acquired resistance to targeted agents may not always be feasible and may not capture the genetic heterogeneity that could exist within a patient.

METHODS

We analyzed circulating tumor DNA (ctDNA) with a large next-generation sequencing panel to characterize the landscape of secondary resistance mechanisms in two independent prospective cohorts of patients (STING: n = 626; BIP: n = 437) with solid tumors who were treated with various types of targeted therapies: tyrosine kinase inhibitors, monoclonal antibodies and hormonal therapies.

RESULTS

Emerging alterations involved in secondary resistance were observed in the plasma of up 34% of patients regardless of the type of targeted therapy. Alterations were polyclonal in up to 14% of patients. Emerging ctDNA alterations were associated with significantly shorter overall survival for patients with some tumor types.

CONCLUSION

This comprehensive landscape of genomic aberrations indicates that genetic alterations involved in secondary resistance to targeted therapy occur frequently and suggests that the detection of such alterations before disease progression may guide personalized treatment and improve patient outcome.

Targeting the Androgen Signaling Axis in Prostate Cancer

Activation of the androgen receptor (AR) and AR-driven transcriptional programs is central to the pathophysiology of prostate cancer. Despite successful translational efforts in targeting AR, therapeutic resistance often occurs as a result of molecular alterations in the androgen signaling axis. The efficacy of next-generation AR-directed therapies for castration-resistant prostate cancer has provided crucial clinical validation for the continued dependence on AR signaling and introduced a range of new treatment options for men with both castration-resistant and castration-sensitive disease. Despite this, however, metastatic prostate cancer largely remains an incurable disease, highlighting the need to better understand the diverse mechanisms by which tumors thwart AR-directed therapies, which may inform new therapeutic avenues. In this review, we revisit concepts in AR signaling and current understandings of AR signaling-dependent resistance mechanisms as well as the next frontier of AR targeting in prostate cancer.

The role of testosterone in men's health: is it time for a new approach?

PURPOSE

Because of many unanswered questions regarding men's health, a literature review was performed to better understand the role of testosterone and testosterone replacement therapy (TRT) in the management of hypogonadism and aging related prostate gland diseases (ARPGD) including prostate cancer (PCa) and benign prostatic hyperplasia (BPH) with lower urinary tract symptoms (LUTS).

METHODS

The PubMed database was screened for pertinent peer reviewed articles published during the last four decades that culminated in the positions and recommendations in this paper.

RESULTS

Hypogonadism seriously impacts men's health, and the diagnosis remains controversial. The incidence of ARPGD is projected to increase worldwide and treatment still has significant limitations. There is compelling evidence that lower, not higher, testosterone levels trigger the development of PCa and BPH through androgen receptor over-expression. TRT was found to be safe and effective in treating hypogonadism including in PCa survivors and those harboring PCa. There is also evidence that TRT might reduce the incidence and prevalence of ARPGD.

CONCLUSIONS AND RECOMMENDATIONS

This review synthesizes a wide-ranging compendium of basic science and clinical research that strongly encourages altering the present approach to diagnosing and treating men with hypogonadism and ARPGD. These findings underscore the importance of avoiding significant testosterone decline and support the use of TRT. Ten recommendations are offered as a framework for the way forward. It is now time for clinicians, payers, researchers, funding agencies, professional associations, and patient advocacy groups to embrace this new paradigm to increase longevity and improve the quality of life.

Apalutamide, Darolutamide and Enzalutamide for Nonmetastatic Castration-Resistant Prostate Cancer (nmCRPC): A Critical Review

Nonmetastatic castration-resistant prostate cancer (nmCRPC) represents a condition in which patients with prostate cancer show biochemical progression during treatment with androgen-deprivation therapy (ADT) without signs of radiographic progression according to conventional imaging. The SPARTAN, ARAMIS and PROSPER trials showed that apalutamide, darolutamide and enzalutamide, respectively, prolong metastasis-free survival (MFS) and overall survival (OS) of nmCRPC patients with a short PSA doubling time, and these antiandrogens have been recently introduced in clinical practice as a new standard of care. No direct comparison of these three agents has been conducted to support treatment choice. In addition, a significant proportion of nmCRPC on conventional imaging is classified as metastatic with new imaging modalities such as the prostate-specific membrane antigen positron emission tomography (PSMA-PET). Some experts posit that these "new metastatic" patients should be treated as mCRPC, resizing the impact of nmCRPC trials, whereas other authors suggest that they should be treated as nmCRPC patients, based on the design of pivotal trials. This review discusses the most convincing evidence regarding the use of novel antiandrogens in patients with nmCRPC and the implications of novel imaging techniques for treatment selection.

PSA response to antiandrogen withdrawal: a systematic review and meta-analysis

BACKGROUND

Antiandrogen withdrawal (AAW) response is the paradoxical decrease in prostate-specific antigen (PSA) following the withdrawal of antiandrogen in patients with advanced prostate cancer. Currently, the reported literature on the proportion of patients exhibiting AAW response and the differences in PSA response between the types of antiandrogens is unclear.

METHODS

This review aimed to explore the PSA response to AAW and to identify if the response depends on the type of antiandrogens. A literature search was performed using databases PubMed, Cochrane and EMBASE with a cut-off date of 23rd of November 2020. Studies reporting on outcomes of AAW and prostate cancer were included. Studies were screened by two reviewers and relevant data extracted. Meta-analysis of outcomes was reported using random-effects and fixed-effects model. A subgroup analysis was performed for type of antiandrogen.

RESULTS

From 450 studies, 23 were included with a total of 1474 patients with advanced prostate cancer were available for further analysis. Overall, 395 (26%) patients had any reduction in PSA levels (95% CI: 20-32%) and 183 (11%) patients had a ≥50% reduction in PSA levels (95% CI: 6-16%). Among the 1212 patients on first-generation antiandrogens, 30% (95% CI: 23-38%) had any PSA decline with 15% patients having a ≥50% PSA decline (95% CI: 8-22%). In contrast, among the 108 patients on second-generation antiandrogens, 7% (95% CI: 0-13%) had any PSA decline and only 1% (95% CI: 0-5%) had a ≥50% PSA decline. Also, among the 154 patients on androgen synthesis inhibitors, 26% (95% CI: 19-33%) had any PSA decline and only 4% (95% CI: 0-13%) had a ≥50% PSA decline.

CONCLUSIONS

One-fourth of patients treated with AAW show a PSA response. However, PSA response to AAW is uncommon with second-generation antiandrogens and androgen synthesis inhibitors. Further research is required to understand the differences in response between the types of antiandrogen.

Treatment and resistance mechanisms in castration-resistant prostate cancer: new implications for clinical decision making?

Introduction: The armamentarium of treatment options in metastatic and non-metastatic CRPC is rapidly evolving. However, the question of how individual treatment decisions should be balanced by available predictive clinical parameters, pharmacogenetic and drug interaction profiles, or compound-associated molecular biomarkers is a major challenge for clinical practice.Areas covered: We discuss treatment and resistance mechanisms in PC with regard to their association to drug efficacy and tolerability. Current efforts of combination treatment and putative predictive biomarkers of available and upcoming compounds are highlighted with regard to their implication on clinical decision-making.Expert opinion: Several treatment approaches are delineated, where identification of resistance mechanisms in CRPC may guide treatment selection. To date, most of these candidate biomarkers will however be found only in a small subset of patients. While current approaches of combination treatment in CRPC are proving synergistic effects on cancer biology, higher complexity with regard to biomarker analysis and interaction profiles of the respective compounds may be expected. Among other aspects of personalized treatment, consideration of drug-drug interaction and pharmacogenetics is an underrepresented issue. However, the non-metastatic castration resistant prostate cancer situation may be an example for treatment selection based on drug interaction profiles in the future.

Enzalutamide for the treatment of nonmetastatic castration-resistant prostate cancer

INTRODUCTION

Enzalutamide is the first characterized second-generation nonsteroidal androgen receptor inhibitor (ARi). Its efficacy has been established in several clinical trials evaluating its role in different settings of prostate cancer. Recently, enzalutamide has been approved for the treatment of nonmetastatic castration-resistant prostate cancer (nmCRPC).

AREAS COVERED

In this paper, the authors describe the chemical structure and pharmacologic characteristics of enzalutamide, providing a summary of clinical trials evaluating its efficacy and safety in prostate cancer patients.

EXPERT OPINION

Enzalutamide adds to the growing arsenal of ARi used in nmCRPC. An improvement in metastasis-free survival was observed with the use of these new treatment options; recently released preliminary data report also an OS benefit. These novel agents are generally well tolerated, but their safety profiles differ slightly. Since head-to-head comparisons between ARi in nmCRPC are lacking, the adverse events profile, as well as drug availability, costs, and considerations on treatment-sequencing, would most likely influence the selection of the individual agent in this setting. Further research is needed to improve treatment selection and clarify many unsolved issues. Abbreviations ARi: nonsteroidal androgen receptor inhibitor; nmCRPC: nonmetastatic castration resistant prostate cancer; ADT: androgen deprivation therapy; OS: overall survival; PSA: prostate specific antigen; FDA: Food and Drug Administration; AR: Androgen Receptor; MFS: metastasis free survival; PSA-DT: PSA doubling time; HR: hazard ratio; CI: confidence interval; AEs: adverse events; mCRPC: metastatic castration resistant prostate cancer; mHSPC: metastatic hormone-sensitive prostate cancer; rPFS: radiographic progression-free survival; OR: odds ratio.

Comprehensive Analysis of AR Alterations in Circulating Tumor DNA from Patients with Advanced Prostate Cancer

BACKGROUND

Somatic alterations in circulating tumor DNA (ctDNA) may be associated with treatment response or prognosis in prostate cancer (PCa). The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in ctDNA from patients with PCa and to further understand the somatic genetic heterogeneity of advanced prostate cancer.

PATIENTS AND METHODS

This study included a heterogeneous group of 892 patients with advanced PCa (predominantly castrate-resistant prostate cancer) with AR alterations detected in ctDNA that underwent next-generation sequencing of 54 to 73 genes via Guardant360 testing (Guardant Health, Inc., Redwood City, CA). Distribution and summary of AR alterations detected, the association of AR alterations with other genes, and a pathway analysis are reported.

RESULTS

The median absolute plasma copy number of AR amplifications was 3.3 (range, 1.2-165.2). Many patients had multiple AR mutations; a total of 112 unique mutations were identified in AR, including L702H (25%), T878A (14%), H875Y (11%), W742C (8%), W742L (4%), F877L (2%), and T878S (2%). Other ctDNA gene alterations in the Guardant assays included TP53 (50%), MYC (34%), BRAF (32%), PIK3CA (29%), MET (25%), CDK6 (26%), EGFR (24%), FGFR1 (21%), and APC (12%). Many of these non-AR alterations are not tissue verified in other studies. AR amplification cosegregated with alterations in MYC (p < .001), BRAF (p < .001), PIK3CA (p < .001), MET (p < .001), CDK6 (p < .001), EGFR (p < .001), FGFR1 (p = .391), and more. Alterations in APC were significantly associated with mutations in AR (p < .001).

CONCLUSION

Several AR alterations and concomitant non-AR alterations that associate with drug resistance were detected. These findings provide additional insights into the heterogeneity of advanced prostate cancer.

IMPLICATIONS FOR PRACTICE

The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in circulating tumor DNA (ctDNA) from patients with prostate cancer in relation to non-AR gene alterations detected in the ctDNA landscape. The study included 892 patients with prostate cancer with AR alterations in ctDNA. AR alterations were significantly associated with other gene alterations detected in ctDNA. The common AR mutations found are linked to resistance to abiraterone, enzalutamide, or bicalutamide. Characterization of the circulating AR landscape and gene alterations provides potential additional insight into the somatic genetic heterogeneity of advanced prostate cancer.

Chinese Expert Consensus on the Diagnosis and Treatment of Castration-Resistant Prostate Cancer (2019 Update)

Currently, the basic treatment of advanced prostate cancer is still endocrine therapy, but almost all patients eventually progress to castration-resistant prostate cancer (CRPC). In 2016, the Chinese Expert Consensus on the Diagnosis and Treatment of CRPC which aimed to help Chinese clinicians formulate treatment plans for CRPC was published. In this 2019 update, the 2016 version was updated with the aim of providing a more appropriate reference for clinical practice, standardizing CRPC patient management, and facilitating decision-making. The consensus is evidence-based and reviews the optimal therapeutic recommendations for CRPC management in China by taking into consideration the clinical characteristics of Chinese patients; drug availability, efficacy and safety; and recent advancements and developments in the international medical arena.

Treatment strategy for metastatic prostate cancer with extremely high PSA level: reconsidering the value of vintage therapy

The prognostic significance of initial prostate-specific antigen (PSA) level for metastatic prostate cancer remains uncertain. We investigated the differences in prognosis and response to hormonal therapies of metastatic prostate cancer patients according to initial PSA levels. We analyzed 184 patients diagnosed with metastatic prostate cancer and divided them into three PSA level groups as follows: low (<100 ng ml⁻¹), intermediate (100–999 ng ml⁻¹), and high (≥1000 ng ml⁻¹). All patients received androgen deprivation therapy (ADT) immediately. We investigated PSA progression-free survival (PFS) for first-line ADT and overall survival (OS) within each of the three groups. Furthermore, we analyzed response to antiandrogen withdrawal (AW) and alternative antiandrogen (AA) therapies after development of castration-resistant prostate cancer (CRPC). No significant differences in OS were observed among the three groups (P = 0.654). Patients with high PSA levels had significantly short PFS for first-line ADT (P = 0.037). Conversely, patients in the high PSA level group had significantly longer PFS when treated with AW than those in the low PSA level group (P = 0.047). Furthermore, patients with high PSA levels had significantly longer PFS when provided with AA therapy (P = 0.049). PSA responders to AW and AA therapies had significantly longer survival after CRPC development than nonresponders (P = 0.011 and P < 0.001, respectively). Thus, extremely high PSA level predicted favorable response to vintage sequential ADT and AW. The current data suggest a novel aspect of extremely high PSA value as a favorable prognostic marker after development of CRPC.

Treatment of non-metastatic castration-resistant prostate cancer: focus on apalutamide

Androgen deprivation therapy (ADT) is an important component of systemic therapy in advanced prostate cancer; however, resistance to ADT is inevitable. Three large studies demonstrated the efficacy of novel androgen receptor (AR)-targeted therapies in prolonging metastasis-free survival and time to symptomatic progression in patients with non-metastatic castration-resistant prostate cancer (nmCRPC). Enzalutamide and apalutamide have been approved by the FDA in the nmCRPC setting. This review discusses the role of AR and ADT in prostate cancer, mechanism of ADT resistance and the nmCRPC stage. In addition, pharmacologic characteristics and clinical development of apalutamide, role of apalutamide in nmCRPC, and ongoing clinical studies of apalutamide in different stages of prostate cancer are discussed.

Switching from a gonadotropin-releasing hormone (GnRH) agonist to a GnRH antagonist in prostate cancer patients: A systematic review and meta-analysis

INTRODUCTION

We sought to address whether there are clinical responses when patients who are failing gonadotropin-releasing hormone (GnRH) agonist therapy are switched to degarelix. Androgen-deprivation therapy remains the backbone of treatment for disseminated prostate cancer and may be achieved with orchiectomy, GnRH agonists, or degarelix, a GnRH antagonist.

METHODS

We conducted a systematic review and meta-analysis with a search of the BIOSIS Previews, Embase, International Pharmaceutical Abstracts, MEDLINE, and Google Scholar databases using key terms. Quantitative meta-analysis was performed to provide a pooled estimate of prostate specific antigen (PSA) response at three months.

RESULTS

Thirteen studies were identified, eight of which were included in the qualitative and quantitative analyses. Patient characteristics were broadly similar between the studies. Out of 155 patients across all included studies, 20 had stable PSA after the switch (12.9%), 14 had a 10-30% decrease in PSA (9.0%), three had a 30-50% decrease (1.9%), and 13 had a more than 50% decrease (8.4%). Random effects meta-analysis of these data demonstrated a pooled response rate of 27.75% (95% confidence interval 18.9-36.5%; I²=7.9%). Changes in testosterone levels following the switch could not be quantitatively assessed due to lack of sufficient data.

CONCLUSIONS

Our results suggest that a switch to GnRH antagonist following progression on a GnRH agonist may result in a stable or decreased PSA at three months in about 30% of patients. This information should be considered among the potential options to discuss with patients with a rising PSA on GnRH agonist therapy.

Apalutamide in the treatment of castrate-resistant prostate cancer: evidence from clinical trials

Apalutamide (ARN-509) is a second-generation androgen receptor (AR) antagonist that was developed to inhibit AR-mediated prostate cancer cell proliferation. Following the initial promising clinical efficacy results in phase I and II clinical trials of patients with metastatic castrate-resistant prostate cancer (CRPC), apalutamide has been investigated in several phase III trials. Particular interest has focused on the development of effective therapy for the prevention of disease progression in patients with nonmetastatic (nm or M0) CRPC, especially patients who have a rapid prostate-specific antigen (PSA) doubling time that is indicative of shorter bone metastasis-free survival and associated with significant morbidity and mortality. The results from the phase III SPARTAN trial were recently published and reported a significant benefit of apalutamide relative to placebo in patients with nmCRPC and a high risk of metastatic progression. The study noted marked improvement in the primary endpoint of metastasis-free survival as well as several relevant secondary clinical endpoints, including time to symptomatic progression. These results led to the United States Food and Drug Administration (US FDA) approval of apalutamide in the nmCRPC setting in February 2018. This review summarizes the clinical development of apalutamide, culminating with the pivotal SPARTAN trial as well as other phase III trials which may further expand potential indications for this agent in the near future.

Management of nonmetastatic castration-resistant prostate cancer

PURPOSE OF REVIEW

The widespread use of prostate-specific antigen (PSA) resulted in stage migration of prostate cancer where androgen deprivation therapy (ADT) is administered for biochemical recurrence in patients following primary treatment. A proportion of these patients progress to a disease state termed nonmetastatic castration-resistant prostate cancer (nmCRPC), with a rising PSA despite ADT and without evidence of metastases on conventional imaging. We will review the treatment options in nmCRPC, especially in light of recent trials showing significant improvement in metastasis-free survival with newer agents.

RECENT FINDINGS

Historically, nmCRPC patients were followed-up if PSA doubling-time (PSADT) exceeded 10 months. Treatment options for patients with shorter PSADT included hormonal manipulations that often resulted in transient PSA decline. Denosumab was found to delay the onset of bone metastasis but did not impact survival. Recently, phase 3 trials showed that second-generation antiandrogens resulted in a significant delay in metastasis and a trend toward survival improvement in a select group of nmCRPC patients.

SUMMARY

The importance of reducing mortality and morbidity associated with metastasis has led to the acceptance of new primary endpoints in the design of trials for nmCRPC and might result in widespread approval of new agents for this disease state.

Nonmetastatic Castration-resistant Prostate Cancer: A Modern Perspective

Nonmetastatic castration-resistant prostate cancer (nmCRPC) presents a challenge to urologists as currently there are no Food and Drug Administration-approved therapies. However, there are new imaging modalities, including fluciclovine positron emission tomography-computed tomography and Ga-PSMA (prostate specific membrane antigent) positron emission tomography-computed tomography, which are improving accuracy of diagnosis. With improved imaging, we are better able to target therapy. Today there are 3 ongoing clinical trials studying second-generation antiandrogens in nmCRPC, which hold the promise of a new treatment paradigm. In this article, we will review the new imaging techniques and the rationale behind novel treatment modalities in nmCRPC.

Antiandrogen withdrawal syndrome (AAWS) in the treatment of patients with prostate cancer

Antiandrogen withdrawal syndrome is an unpredictable event diagnosed in patients with hormone-sensitive prostate cancer treated with combined androgen blockade therapy. It is defined by prostate-specific antigen value reduction, occasionally associated with a radiological response, that occurs 4-6 weeks after first-generation antiandrogen therapy discontinuation. New-generation hormonal therapies, such as enzalutamide and abiraterone acetate, improved the overall survival in patients with metastatic castration-resistant prostate cancer, and recent trials have also shown the efficacy of abiraterone in hormone-sensitive disease. In the last few years, several case reports and retrospective studies suggested that the withdrawal syndrome may also occur with these new drugs. This review summarizes literature data and hypothesis about the biological rationale underlying the syndrome and its potential clinical relevance, focusing mainly on new-generation hormonal therapies. Several in vitro studies suggest that androgen receptor gain-of-function mutations are involved in this syndrome, shifting the antiandrogen activity from antagonist to agonist. Several different drug-specific point mutations have been reported. The association of the withdrawal syndrome for enzalutamide and abiraterone needs confirmation by additional investigations. However, new-generation hormonal therapies being increasingly used in all stages of disease, more patients may experience the syndrome when stopping the treatment at the time of disease progression, although the clinical relevance of this phenomenon in the management of metastatic castration-resistant prostate cancer remains to be defined.

Androgen deprivation therapy for the treatment of prostate cancer: a focus on pharmacokinetics

INTRODUCTION

Medical therapy has undergone many changes as our understanding of prostate cancer cell biology has improved. Androgen deprivation therapy (ADT) remains the mainstay of therapy for metastatic disease. Metastatic castrate-resistant prostate cancer (CRPC) is an important concern since we are unable to stop progression with currently available agents. Areas covered: Pharmacologic ADT is the most commonly used treatment for metastatic prostate cancer. Multiple agents are available for both first-line and second-line use: antiandrogens, estrogens, luteinizing hormone-releasing hormone agonists/antagonists, and CYP17 inhibitors. With adoption of these drugs, it is important to consider their pharmacokinetic and pharmacodynamic properties. Many undergo metabolism through cytochrome P450. Levels may be altered with co-administration of drugs acting as enzyme inhibitors or inducers. Understanding mechanism of action, metabolism, and excretion of these drugs allows clinicians to provide the best therapeutic care while minimizing adverse events. Expert opinion: Many men with metastatic prostate cancer will progress to castration resistance. An understanding of resistance mechanisms at the cellular level has revealed new drug targets with hopes of halting or reversing progression of metastatic disease. Second-line agents, traditionally reserved for CRPC, are being studied in metastatic castrate-sensitive prostate cancer, and may offer practice-changing evidence supporting their use.

Incidence and Characterization of Antiandrogen Withdrawal Syndrome After Discontinuation of Treatment With Enzalutamide in Castration-resistant Prostate Cancer

BACKGROUND

Antiandrogen withdrawal syndrome (AAWS), manifested as a prostate-specific antigen (PSA) decline after discontinuation of a first-generation antiandrogen has been well characterized. The objective of the present study was to assess the incidence of AAWS with enzalutamide in men with metastatic castration-resistant prostate cancer.

PATIENTS AND METHODS

Patients from a single-institution cohort with metastatic castration-resistant prostate cancer who had discontinued enzalutamide after PSA or radiographic progression were included. AAWS after enzalutamide was defined as any PSA decline after discontinuation of enzalutamide. The baseline patient, disease, and treatment characteristics were compared between patients with and without AAWS after enzalutamide. Statistical analysis of the baseline characteristics included descriptive statistics using the Wilcoxon rank sum test and the Fisher exact test. The median duration of enzalutamide therapy was compared using the log-rank test, and the progression-free survival of the patients with AAWS was evaluated using the Kaplan-Meier method.

RESULTS

Of 47 eligible patients, 5 experienced AAWS after enzalutamide discontinuation. The PSA response in these 5 patients was 84%, 32%, 17%, 15%, and 15%. The median AAWS response time until subsequent PSA progression was 3.3 months. No patient, disease, or treatment characteristics differed among the patients with and without AAWS after enzalutamide discontinuation.

CONCLUSION

To the best of our knowledge, this is the largest reported cohort documenting the incidence and characterization of AAWS after enzalutamide to date. The AAWS frequency after enzalutamide was low and of short duration. No patient- or disease-related characteristics were associated with AAWS with enzalutamide. The occurrence of AAWS after enzalutamide was not clinically meaningful. Thus, accounting for this phenomenon in clinical practice or trial designs could be unnecessary.

Therapies for castration-resistant prostate cancer in a new era: The indication of vintage hormonal therapy, chemotherapy and the new medicines

When advanced prostate cancer recurred during hormonal therapy and became the castration-resistant prostate cancer, "vintage hormonal therapy," such as antiandrogen alternating therapy or estrogen-related hormonal therapy, was widely carried out in Japan until 2013. This vintage hormonal therapy controlled the progression of castration-resistant prostate cancer. When castration-resistant prostate cancer relapses during these therapies, chemotherapy using docetaxel has been carried out subsequently. Since new hormonal therapies using abiraterone acetate and enzalutamide, which improve the prognosis of castration-resistant prostate cancer, became available in Japan from 2014, therapeutic options for castration-resistant prostate cancer have increased. Furthermore, the improvement of the further prognosis is promising by using cabazitaxel for docetaxel-resistant castration-resistant prostate cancer and radium-223 for castration-resistant prostate cancer with bone metastasis. An increase in therapeutic options gives rise to many questions, including best timing to use them and the indication. Furthermore, physicians have to consider the treatment for the recurrence after having carried out chemotherapy. We want to argue the difference in hormonal therapy between Japan and Western countries, and problems when carrying out new treatments, and the importance of imaging in the present review article.

Molecular mechanisms underlying resistance to androgen deprivation therapy in prostate cancer

Prostate cancer (PCa) is the most widely diagnosed male cancer in the Western World and while low- and intermediate-risk PCa patients have a variety of treatment options, metastatic patients are limited to androgen deprivation therapy (ADT). This treatment paradigm has been in place for 75 years due to the unique role of androgens in promoting growth of prostatic epithelial cells via the transcription factor androgen receptor (AR) and downstream signaling pathways. Within 2 to 3 years of ADT, disease recurs-at which time, patients are considered to have castration-recurrent PCa (CR-PCa). A universal mechanism by which PCa becomes resistant to ADT has yet to be discovered. In this review article, we discuss underlying molecular mechanisms by which PCa evades ADT. Several major resistance pathways center on androgen signaling, including intratumoral and adrenal androgen production, AR-overexpression and amplification, expression of AR mutants, and constitutively-active AR splice variants. Other ADT resistance mechanisms, including activation of glucocorticoid receptor and impairment of DNA repair pathways are also discussed. New therapies have been approved for treatment of CR-PCa, but increase median survival by only 2-8 months. We discuss possible mechanisms of resistance to these new ADT agents. Finally, the practicality of the application of "precision oncology" to this continuing challenge of therapy resistance in metastatic or CR-PCa is examined. Empirical validation and clinical-based evidence are definitely needed to prove the superiority of "precision" treatment in providing a more targeted approach and curative therapies over the existing practices that are based on biological "cause-and-effect" relationship.

Long-term complete response of antiandrogen withdrawal syndrome in a patient with metastatic prostate cancer: A case report

Antiandrogen withdrawal syndrome (AWS) is a well-established phenomenon in prostate cancer treated with combined androgen blockade (CAB). AWS is generally defined as subjective and/or objective improvement following discontinuation of an antiandrogen. However, the duration of the AWS response is usually limited. In addition, a complete response is quite rare. We herein present the case of a patient who achieved complete response from AWS, with the duration of this response lasting for >6 years. A 72-year-old man with metastatic prostate cancer received CAB with a luteinizing hormone-releasing hormone analog and bicalutamide. In addition, for local cancer control, external beam radiation therapy (70 Gy) to the prostate was performed. Subsequently, the serum prostate-specific antigen (PSA) level reached a nadir (undetectable level). Four years later, the patient's serum PSA level started to rise, and bicalutamide was discontinued to confirm AWS at a serum PSA level of 0.34 ng/ml. The PSA level immediately decreased again to an undetectable level (0.00 ng/ml), where it has been remained for 6 years. Bone scintigraphy and computed tomography scans have shown no evidence of bone or other metastases since the introduction of AWS. To the best of our knowledge, there have been no reports of such a long duration of complete response from AWS. Therefore, this phenomenon should always be considered, even in patients with advanced disease.

Impact of the 2010 Consensus Recommendations of the Clinical Trial Design Task Force of the NCI Investigational Drug Steering Committee

Oncology phase III trials have a high failure rate, leading to high development costs. The Clinical Trials Design Task Force of the Investigational Drug Steering Committee of the NCI Cancer Therapy and Evaluation Program developed Recommendations regarding the design of phase II trials. We report here on the results of a Concordance Group review charged with documenting whether concordance rates improved after the publication of the Recommendations. One hundred and fifty-five trials were reviewed. Letter of Intents (LOI) from the post-Recommendation period were more likely to be randomized (44% vs. 34%) and biomarker selected (19% vs. 10%). Single-arm studies using time-to-event endpoints (benchmarked against historical data) were similar, as was the type of tumor. There was a significant improvement in the rate of concordance, with 74% of LOIs scored as concordant compared with 58% before the Recommendations (P = 0.042). This included a marked decrease in the use of single-arm designs to evaluate the activity of drug combinations (19% vs. 5%, P = 0.009). There were areas for which clarification was warranted, including the need for protocols to include further development plans, the use of realistic benchmarks, the careful evaluation of historical controls, and the use of a standard treatment option as a control. Ongoing critical evaluation of current trial design methodology and the development of new Guidelines when appropriate will continue to improve drug development ensuring that safe and effective cancer therapeutics are made available to our patients as quickly and efficiently as possible.

Cellular androgen content influences enzalutamide agonism of F877L mutant androgen receptor

Prostate cancer is the most commonly diagnosed and second-most lethal cancer among men in the United States. The vast majority of prostate cancer deaths are due to castration-resistant prostate cancer (CRPC) - the lethal form of the disease that has progressed despite therapies that interfere with activation of androgen receptor (AR) signaling. One emergent resistance mechanism to medical castration is synthesis of intratumoral androgens that activate the AR. This insight led to the development of the AR antagonist enzalutamide. However, resistance to enzalutamide invariably develops, and disease progression is nearly universal. One mechanism of resistance to enzalutamide is an F877L mutation in the AR ligand-binding domain that can convert enzalutamide to an agonist of AR activity. However, mechanisms that contribute to the agonist switch had not been fully clarified, and there were no therapies to block AR F877L. Using cell line models of castration-resistant prostate cancer (CRPC), we determined that cellular androgen content influences enzalutamide agonism of mutant F877L AR. Further, enzalutamide treatment of AR F877L-expressing cell lines recapitulated the effects of androgen activation of F877L AR or wild-type AR. Because the BET bromodomain inhibitor JQ-1 was previously shown to block androgen activation of wild-type AR, we tested JQ-1 in AR F877L-expressing CRPC models. We determined that JQ-1 suppressed androgen or enzalutamide activation of mutant F877L AR and suppressed growth of mutant F877L AR CRPC tumors in vivo, demonstrating a new strategy to treat tumors harboring this mutation.

The Effect of F877L and T878A Mutations on Androgen Receptor Response to Enzalutamide

Treatment-induced mutations in the ligand-binding domain of the androgen receptor (AR) are known to change antagonists into agonists. Recently, the F877L mutation has been described to convert enzalutamide into an agonist. This mutation was seen to co-occur in the endogenous AR allele of LNCaP cells, next to the T878A mutation. Here, we studied the effects of enzalutamide on the F877L and T878A mutants, as well as the double-mutant AR (F877L/T878A). Molecular modeling revealed favorable structural changes in the double-mutant AR that lead to a decrease in steric clashes for enzalutamide. Ligand-binding assays confirmed that the F877L mutation leads to an increase in relative binding affinity for enzalutamide, but only the combination with the T878A mutation resulted in a strong agonistic activity. This correlated with changes in coregulator recruitment and chromatin interactions. Our data show that enzalutamide is only a very weak partial agonist of the AR F877L, and a strong partial agonist of the double-mutant AR. Mol Cancer Ther; 15(7); 1702-12. ©2016 AACR.

Saudi oncology society and Saudi urology association combined clinical management guidelines for prostate cancer

This is an update to the previously published Saudi guidelines for the evaluation, medical, and surgical management of patients diagnosed with prostate cancer. It is categorized according to the stage of the disease using the tumor node metastasis staging system 7(th) edition. The guidelines are presented with supporting evidence level, they are based on comprehensive literature review, several internationally recognized guidelines, and the collective expertise of the guidelines committee members (authors) who were selected by the Saudi oncology society and Saudi urological association. Considerations to the local availability of drugs, technology, and expertise have been regarded. These guidelines should serve as a roadmap for the urologists, oncologists, general physicians, support groups, and health care policy makers in the management of patients diagnosed with adenocarcinoma of the prostate to.

Enzalutamide: a review of its use in chemotherapy-naïve metastatic castration-resistant prostate cancer

Enzalutamide (Xtandi(®)) is an androgen receptor inhibitor that blocks several steps in the androgen receptor signalling pathway. This article reviews the clinical efficacy and tolerability of oral enzalutamide in chemotherapy-naïve men with metastatic castration-resistant prostate cancer (CRPC), as well as summarizing its pharmacological properties. In the randomized, double-blind, multinational PREVAIL trial, enzalutamide significantly improved both radiographic progression-free survival and overall survival versus placebo in chemotherapy-naïve men with metastatic CRPC who were asymptomatic or mildly symptomatic. In addition, enzalutamide significantly delayed the need for chemotherapy and the decline in health-related quality of life versus placebo. Enzalutamide was generally well tolerated in chemotherapy-naïve men with metastatic CRPC. In conclusion, enzalutamide is a convenient, effective and well tolerated treatment for chemotherapy-naïve men with metastatic CRPC who are asymptomatic or mildly symptomatic.

Clinical outcomes of anti-androgen withdrawal and subsequent alternative anti-androgen therapy for advanced prostate cancer following failure of initial maximum androgen blockade

The present study aimed to investigate the significance of anti-androgen withdrawal and/or subsequent alternative anti-androgen therapy in patients with advanced prostate cancer (PC) who relapsed after initial maximum androgen blockade (MAB). The present study evaluated the clinical outcomes of 272 consecutive advanced PC patients undergoing anti-androgen withdrawal and/or subsequent alternative anti-androgen therapy with flutamide following the failure of initial MAB using bicalutamide. With the exception of 41 patients (15.1%) who did not undergo anti-androgen withdrawal due to the characteristics of PC suggesting aggressive diseases, prostate-specific antigen (PSA) declined from the baseline value in 83 patients (35.9%), including 18 (7.8%) with PSA decline >50%, but not in the remaining 148 (64.1%). No significant difference in the overall survival (OS) or cancer-specific survival (CSS) among the three groups was observed based on the response to anti-androgen withdrawal. Following the introduction of alternative anti-androgen therapy with flutamide, PSA decline was observed in 185 patients (68.0%), including 103 (37.9%) who achieved a PSA reduction of >50%; however, the PSA level continued to elevate in the remaining 87 (32.0%). Furthermore, of the numerous factors examined, only the duration of the initial MAB therapy was shown to be significantly correlated with the PSA decline following alternative anti-androgen therapy. Multivariate analysis of several factors identified revealed that only PSA decline following alternative anti-androgen therapy was an independent predictor of CSS and OS. If initial MAB is effective, the introduction of alternative anti-androgen therapy may be considered; however, anti-androgen withdrawal should be omitted, irrespective of the characteristics of advanced PC.

Switching and withdrawing hormonal agents for castration-resistant prostate cancer

The antiandrogen withdrawal syndrome (AAWS) is characterized by tumour regression and a decline in serum PSA on discontinuation of antiandrogen therapy in patients with prostate cancer. This phenomenon has been best described with the withdrawal of the nonsteroidal antiandrogens, bicalutamide and flutamide, but has also been reported with a wide range of hormonal agents. Mutations that occur in advanced prostate cancer and induce partial activation of the androgen receptor (AR) by hormonal agents have been suggested as the main causal mechanism of the AAWS. Corticosteroids, used singly or in conjunction with abiraterone, docetaxel and cabazitaxel might also be associated with the AAWS. The discovery of the Phe876Leu mutation in the AR, which is activated by enzalutamide, raises the possibility of withdrawal responses to novel hormonal agents. This Review focusses on the molecular mechanisms responsible for withdrawal responses, the role of AR mutations in the development of treatment resistance, and the evidence for the sequential use of antiandrogens in prostate cancer therapy. The implications of AR mutations for the development of novel drugs that target the AR are discussed, as are the challenges associated with redefining the utility of older treatments in the current therapeutic landscape.

Prior administration of a non-steroidal anti-androgen failed to prevent the flare-up caused by a luteinizing hormone-releasing hormone agonist in a patient with metastatic prostate cancer

Background

‘Flare phenomenon’ after initial luteinizing hormone-releasing hormone agonist administration is a widely approved concept in the treatment of prostate cancer. In most guidelines, concomitant therapy with anti-androgens is recommended to prevent this flare phenomenon. However, there are few reports describing serum prostate-specific antigen transitions after hormonal therapy. Here, we present a case of a man who experienced the biochemical and clinical flare phenomenon despite prior anti-androgen use and who has detailed data.

Case presentation

A 70-year-old Asian man with metastatic prostate cancer (multiple bone) was referred to our hospital. He was treated with prior anti-androgens and luteinizing hormone-releasing hormone agonist. Regardless of prior use of anti-androgens, his low back pain caused by bone metastases was deteriorated and serum prostate-specific antigen level was raised from 974.8 ng/mL to 2,555.5 ng/mL within 3 weeks. Then, his serum prostate specific antigen level started to decrease along with the pain. The nadir reached 1.0 ng/mL and remained for 6 months. Because the serum level of prostate-specific antigen then began to increase again, anti-androgen was discontinued for anti-androgen withdrawal syndrome. Then the serum level decreased again to less than 0.1 ng/mL. Until now, his serum prostate-specific antigen level has been maintained at less than 0.1 ng/mL for more than 30 months without any clinical progressions.

Conclusion

We present the case of a patient in whom a clinical flare caused by an leuteinizing hormone-releasing hormone agonist was not prevented by prior anti-androgen administration. In addition, the nadir level of prostate-specific antigen when he received leuteinizing hormone-releasing hormone monotherapy was ten times lower than when he received concomitant therapy, and period of anti-androgen withdrawal syndrome was longer than usual. In this case, anti-androgen was probably not effective from the initial administration. Awareness of the possibility of ineffectiveness of anti-androgens is important in the treatment of symptomatic metastatic prostate cancer. Leuteinizing hormone-releasing hormone antagonist and surgical castration is a more reliable clinical approach for the prostate cancer patients with symptomatic metastatic disease.

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.

Targeting the androgen receptor in prostate and breast cancer: several new agents in development

Prostate cancer (PCa) and breast cancer (BCa) share similarities as hormone-sensitive cancers with a wide heterogeneity of both phenotype and biology. The androgen receptor (AR) is a hormone receptor involved in both benign and malignant processes. Targeting androgen synthesis and the AR pathway has been and remains central to PCa therapy. Recently, there has been increased interest in the role of the AR in BCa development and growth, with results indicating AR co-expression with estrogen, progesterone, and human epidermal growth factor receptors, across all intrinsic subtypes of BCa. Targeting the AR axis is an evolving field with novel therapies in development which may ultimately be applicable to both tumor types. In this review, we offer an overview of available agents which target the AR axis in both PCa and BCa and provide insights into the novel drugs in development for targeting this signaling pathway.

Uroncor consensus statement: Management of biochemical recurrence after radical radiotherapy for prostate cancer: From biochemical failure to castration resistance

Management of patients who experience biochemical failure after radical radiotherapy with or without hormonal therapy is highly challenging. The clinician must not only choose the type of treatment, but also the timing and optimal sequence of treatment administration. When biochemical failure occurs, numerous treatment scenarios are possible, thus making it more difficult to select the optimal approach. Moreover, rapid and ongoing advances in treatment options require that physicians make decisions that could impact both survival and quality of life. The aim of the present consensus statement, developed by the Urological Tumour Working Group (URONCOR) of the Spanish Society of Radiation Oncology (SEOR), is to provide cancer specialists with the latest, evidence-based information needed to make the best decisions for the patient under all possible treatment scenarios. The structure of this consensus statement follows the typical development of disease progression after biochemical failure, with the most appropriate treatment recommendations given for each stage. The consensus statement is organized into three separate chapters, as follows: biochemical failure with or without local recurrence and/or metastasis; progression after salvage therapy; and treatment of castration-resistant patients.

Progress in antiandrogen design targeting hormone binding pocket to circumvent mutation based resistance

Androgen receptor (AR) plays a critical role in the development and progression of prostate cancer (PCa). Current clinically used antiandrogens such as flutamide, bicalutamide, and newly approved enzalutamide mainly target the hormone binding pocket (HBP) of AR. However, over time, drug resistance invariably develops and switches these antiandrogens from antagonist to agonist of the AR. Accumulated evidence indicates that AR mutation is an important cause for the drug resistance. This review will give an overview of the mutation based resistance of the current clinically used antiandrogens and the rational drug design to overcome the resistance, provides a promising strategy for the development of the new generation of antiandrogens targeting HBP.

Sequential maximum androgen blockade (MAB) in minimally symptomatic prostate cancer progressing after initial MAB: two case reports

The management of castrate-resistant prostate cancer progressing after maximum androgen blockade (MAB) has evolved in the last decade with the development of several novel therapeutic options. However, the initial therapeutic strategy in these patients usually involves withdrawal of anti-androgen that can be associated with biochemical response in approximately 20% of patients. Notably, we have observed evidence of sustained biochemical response in two patients following second- and third-line MAB using rechallenge schedule of previously administered anti-androgen after latent interval. The possibility of response following sequential MAB using the same anti-androgen agent has not yet been reported.