Sequencing of agents in castration-resistant prostate cancer

Osteoblast-Derived ECM1 Promotes Anti-Androgen Resistance in Bone Metastatic Prostate Cancer

Acquired resistance to hormonal therapy, particularly enzalutamide (ENZ), remains a significant obstacle in the treatment of advanced bone metastatic prostate cancer. Here, it is demonstrated that under ENZ treatment, osteoblasts in the bone microenvironment secrete increased levels of extracellular matrix protein 1 (ECM1), which affects surrounding prostate cancer cells, promoting tumor cell proliferation and anti-androgen resistance. Mechanistically, ECM1 interacts with the enolase 1 (ENO1) receptor on the prostate cancer cell membrane, leading to its phosphorylation at the Y189 site. This event further recruits adapter proteins including growth factor receptor-bound protein 2 (GRB2) and son of sevenless homolog 1 (SOS1), which activates the downstream mitogen-activated protein kinase (MAPK) signaling pathway to induce anti-androgen resistance. Furthermore, inhibiting ECM1 or utilizing the ENO1-targeting inhibitor phosphonoacetohydroxamate (PhAH) significantly restores tumor cell sensitivity to ENZ. Taken together, a potential mechanism is identified through which osteoblast-derived ECM1 drives resistance in bone metastatic prostate cancer under ENZ treatment. Additionally, the findings indicate that ECM1 and ENO1 may serve as potential targets for developing therapies for bone metastatic castration-resistant prostate cancer.

Contemporary Treatment Patterns and Oncological Outcomes of Metastatic Hormone-sensitive Prostate Cancer and First- to Sixth- line Metastatic Castration-resistant Prostate Cancer Patients

Background and objective

With approval of novel systemic therapies within the past decade for metastatic hormone-sensitive (mHSPC) and castration-resistant (mCRPC) prostate cancer, patients may receive several therapy lines. However, the use of these treatments is under an ongoing change. We investigated contemporary treatment trends and progression-free (PFS) and overall (OS) survival of different therapy lines.

Methods

Relying on our institutional tertiary-care database, we identified mHSPC and mCRPC patients. The main outcome consisted of treatment changes (estimated annual percentage change [EAPC]) within the past decade, as well as PFS and OS for different mHSPC and mCRPC treatment lines.

Key findings and limitations

In 1098 metastatic patients, the median age was 70 yr with a median of two systemic therapy lines. For first-line mCRPC between 2013 and 2023, androgen deprivation monotherapy (ADT) monotherapy usage decreased significantly from 31% to 0% (EAPC -38.3%, p < 0.001), while the administration of chemotherapy increased from 16.7% to 33.3% (EAPC: +10.1%, p < 0.001). The PFS/OS rates of mHSPC patients was 21/67 mo, and those for first-, second-, third-, fourth-, fifth-, and sixth-line mCRPC patients were 11/47, eight of 30, seven of 24, six of 19, seven of 17, and seven of 13 mo, respectively. With an increased number of new combination therapy lines received, the median OS in mCRPC improved from 26 mo (one systemic treatment) to 52 mo (two or more lines of systemic treatment).

Conclusions and clinical implications

Significant changes in treatment patterns could be observed for mHSPC and mCRPC patients within the past decade, and usage of ADT monotherapy has decreased rapidly in real-world practice. Moreover, PFS decreases significantly with every therapy line, and OS increases with the implementation of new therapies.

Patient summary

Improvements in the real-world setting regarding the usage of combination therapies for metastatic hormone-sensitive and castration-resistant prostate cancer were made, which is reflected in contemporary survival outcomes.

Co-targeting SKP2 and KDM5B inhibits prostate cancer progression by abrogating AKT signaling with induction of senescence and apoptosis

BACKGROUND

Prostate cancer (PCa) is the second-leading cause of cancer mortalities in the United States and is the most commonly diagnosed malignancy in men. While androgen deprivation therapy (ADT) is the first-line treatment option to initial responses, most PCa patients invariably develop castration-resistant PCa (CRPC). Therefore, novel and effective treatment strategies are needed. The goal of this study was to evaluate the anticancer effects of the combination of two small molecule inhibitors, SZL-P1-41 (SKP2 inhibitor) and PBIT (KDM5B inhibitor), on PCa suppression and to delineate the underlying molecular mechanisms.

METHODS

Human CRPC cell lines, C4-2B and PC3 cells, were treated with small molecular inhibitors alone or in combination, to assess effects on cell proliferation, migration, senescence, and apoptosis.

RESULTS

SKP2 and KDM5B showed an inverse regulation at the translational level in PCa cells. Cells deficient in SKP2 showed an increase in KDM5B protein level, compared to that in cells expressing SKP2. By contrast, cells deficient in KDM5B showed an increase in SKP2 protein level, compared to that in cells with KDM5B intact. The stability of SKP2 protein was prolonged in KDM5B depleted cells as measured by cycloheximide chase assay. Cells deficient in KDM5B were more vulnerable to SKP2 inhibition, showing a twofold greater reduction in proliferation compared to cells with KDM5B intact (p < 0.05). More importantly, combined inhibition of KDM5B and SKP2 significantly decreased proliferation and migration of PCa cells as compared to untreated controls (p < 0.005). Mechanistically, combined inhibition of KDM5B and SKP2 in PCa cells abrogated AKT activation, resulting in an induction of both cellular senescence and apoptosis, which was measured via Western blot analysis and senescence-associated β-galactosidase (SA-β-Gal) staining.

CONCLUSIONS

Combined inhibition of KDM5B and SKP2 was more effective at inhibiting proliferation and migration of CRPC cells, and this regimen would be an ideal therapeutic approach of controlling CRPC malignancy.

Impact of Circulating Tumor Cell-Expressed Prostate-Specific Membrane Antigen and Prostate-Specific Antigen Transcripts in Different Stages of Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA)-based images, which visually quantify PSMA expression, are used to determine prostate cancer micrometastases. This study evaluated whether a circulating tumor cell (CTC)-based transcript platform, including PSMA mRNA, could help identify potential prognostic markers in prostate cancer.

EXPERIMENTAL DESIGN

We prospectively enrolled 21 healthy individuals and 247 patients with prostate cancer [localized prostate cancer (LPCa), n = 94; metastatic hormone-sensitive prostate cancer (mHSPC), n = 44; and metastatic castration-resistant prostate cancer (mCRPC), n = 109]. The mRNA expression of six transcripts [PSMA, prostate-specific antigen (PSA), AR, AR-V7, EpCAM, and KRT 19] from CTCs was measured, and their relationship with biochemical recurrence (BCR) in LPCa and mCRPC progression-free survival (PFS) rate in mHSPC was assessed. PSA-PFS and radiological-PFS were also calculated to identify potential biomarkers for predicting androgen receptor signaling inhibitor (ARSI) and taxane-based chemotherapy resistance in mCRPC.

RESULTS

CTC detection rates were 75.5%, 95.3%, and 98.0% for LPCa, mHSPC, and mCRPC, respectively. In LPCa, PSMA [hazard ratio (HR), 3.35; P = 0.028) and PSA mRNA (HR, 1.42; P = 0.047] expressions were associated with BCR. Patients with mHSPC with high PSMA (HR, 4.26; P = 0.020) and PSA mRNA (HR, 3.52; P = 0.042) expressions showed significantly worse mCRPC-PFS rates than those with low expression. Increased PSA and PSMA mRNA expressions were significantly associated with shorter PSA-PFS and radiological PFS in mCPRC, indicating an association with drug resistance.

CONCLUSIONS

PSMA and PSA mRNA expressions are associated with BCR in LPCa. In advanced prostate cancer, PSMA and PSA mRNA can also predict rapid progression from mHSPC to mCRPC and ARSI or taxane-based chemotherapy resistance.

Newly developed preclinical models reveal broad-spectrum CDK inhibitors as potent drugs for CRPC exhibiting primary resistance to enzalutamide

Androgen-deprivation therapy is a standard treatment for advanced prostate cancer. However, most patients eventually acquire resistance and progress to castration-resistant prostate cancer (CRPC). In this study, we established new CRPC cell lines, AILNCaP14 and AILNCaP15, from LNCaP cells under androgen-deprived conditions. Unlike most pre-existing CRPC cell lines, both cell lines expressed higher levels of androgen receptor (AR) and prostate-specific antigen (PSA) than parental LNCaP cells. Moreover, these cells exhibited primary resistance to enzalutamide. Since AR signaling plays a significant role in the development of CRPC, PSA promoter sequences fused with GFP were introduced into AILNCaP14 cells to conduct GFP fluorescence-based chemical screening. We identified flavopiridol, a broad-spectrum CDK inhibitor, as a candidate drug that could repress AR transactivation of CRPC cells, presumably through the inhibition of phosphorylation of AR on the serine 81 residue (pARSer81 ). Importantly, this broad-spectrum CDK inhibitor inhibited the proliferation of AILNCaP14 cells both in vitro and in vivo. Moreover, a newly developed liver metastatic model using AILNCaP15 cells revealed that the compound attenuated tumor growth of CRPC harboring highly metastatic properties. Finally, we developed a patient-derived xenograft (PDX) model of CRPC and DCaP CR from a patient presenting therapeutic resistance to enzalutamide, abiraterone, and docetaxel. Flavopiridol successfully suppressed the tumor growth of CRPC in this PDX model. Since ARSer81 was found to be phosphorylated in clinical CRPC samples, our data suggested that broad-spectrum CDK inhibitors might be a potent candidate drug for the treatment of CRPC, including those exhibiting primary resistance to enzalutamide.

[Guidelines for Evaluating Treatment Response Based on Bone Scan for Metastatic Castration-Resistant Prostate Cancer: Prostate Cancer Clinical Trial Working Group 3 Recommendations]

In prostate cancer, the bone is the most common site of metastasis, and it is essential to evaluate metastatic bone lesions to assess the tumor burden and treatment response. Castration-resistant prostate cancer refers to the state wherein the cancer continues to progress despite a significant reduction of the sex hormone level and is associated with frequent distant metastasis. The Prostate Cancer Working Group 3 (PCWG3) released guidelines that aimed to standardize the assessment of treatment effects in castration-resistant prostate cancer using bone scintigraphy. However, these guidelines can be challenging to comprehend and implement in practical settings. The purpose of this review was to provide an overview of a specific image acquisition method and treatment response assessment for bone scintigraphy-based evaluation of bone lesions in metastatic castration-resistant prostate cancer, in accordance with the PCWG3 guidelines.

Canonical and truncated transglutaminase-2 regulate mucin-1 expression and androgen independency in prostate cancer cell lines

Androgen independency is associated with poor prostate cancer (PCa) survival. Here we report that silencing of transglutaminase-2 (TG2) expression by CRISPR-Cas9 is associated with upregulation of androgen receptor (AR) transcription in PCa cell lines. Knockout of TG2 reversed the migratory potential and anchorage independency of PC3 and DU145 cells and revealed a reduced level of mucin-1 (MUC1) RNA transcript through unbiased multi-omics profiling, which was restored by selective add-back of the truncated TG2 isoform (TGM2_v2). Silencing of AR resulted into increased MUC1 in TG2KO PC3 cells showing that TG2 affects transcriptional regulation of MUC1 via repressing AR expression. Treatment of PC3 WT cell line with TG2 inhibitor ZDON led to a significant increase in AR expression and decrease in MUC1. ZDON also blocked the formation of MUC1-multimers labelled with TG amine-donor substrates in reducing conditions, revealing for the first time a role for TG2, which we show to be externalised via extracellular vesicles, in MUC1 stabilisation via calcium-dependent transamidation. A specific antibody towards TGM2_v2 revealed its restricted nuclear location compared to the canonical long form of TG2 (TGM2_v1), which is predominantly cytosolic, suggesting that this form contributes to the previously suggested TG2-mediated NF-κB activation and AR transcriptional repression. As TGM2_v2 transcription was increased in biopsies of early-stage prostate adenocarcinoma (PRAD) patients compared to subjects presenting inflammatory prostatitis, and total TG2 protein expression significantly increased in PRAD versus normal tissue, the role of TG2 and its truncated form as a prostate malignancy marker is suggested. In conclusion, this investigation has provided the first unbiased discovery of a novel pathway mediated by TG2 via MUC1, which is shown to contribute to androgen insensitivity and malignancy of PCa cells and be upregulated in PCa biopsies, with potential relevance to cancer immune evasion.

Infectivity-Enhanced, Conditionally Replicative Adenovirus for COX-2-Expressing Castration-Resistant Prostate Cancer

BACKGROUND

The development of conditionally replicative adenoviruses (CRAds) for castration-resistant prostate cancer (CRPC), particularly neuroendocrine prostate cancer (NEPC), has two major obstacles: choice of control element and poor infectivity. We applied fiber-modification-based infectivity enhancement and an androgen-independent promoter (cyclooxynegase-2, COX-2) to overcome these issues.

METHODS

The properties of the COX-2 promoter and the effect of fiber modification were tested in two CRPC cell lines (Du-145 and PC3). Fiber-modified COX-2 CRAds were tested in vitro for cytocidal effect as well as in vivo for antitumor effect with subcutaneous CRPC xenografts.

RESULTS

In both CRPC cell lines, the COX-2 promoter showed high activity, and Ad5/Ad3 fiber modification significantly enhanced adenoviral infectivity. COX-2 CRAds showed a potent cytocidal effect in CRPC cells with remarkable augmentation by fiber modification. In vivo, COX-2 CRAds showed an antitumor effect in Du-145 while only Ad5/Ad3 CRAd showed the strongest antitumor effect in PC3.

CONCLUSION

COX-2 promoter-based, infectivity-enhanced CRAds showed a potent antitumor effect in CRPC/NEPC cells.

Plk1 Inhibitors and Abiraterone Synergistically Disrupt Mitosis and Kill Cancer Cells of Disparate Origin Independently of Androgen Receptor Signaling

Abiraterone is a standard treatment for metastatic castrate-resistant prostate cancer (mCRPC) that slows disease progression by abrogating androgen synthesis and antagonizing the androgen receptor (AR). Here we report that inhibitors of the mitotic regulator polo-like kinase-1 (Plk1), including the clinically active third-generation Plk1 inhibitor onvansertib, synergizes with abiraterone in vitro and in vivo to kill a subset of cancer cells from a wide variety of tumor types in an androgen-independent manner. Gene-expression analysis identified an AR-independent synergy-specific gene set signature upregulated upon abiraterone treatment that is dominated by pathways related to mitosis and the mitotic spindle. Abiraterone treatment alone caused defects in mitotic spindle orientation, failure of complete chromosome condensation, and improper cell division independently of its effects on AR signaling. These effects, although mild following abiraterone monotherapy, resulted in profound sensitization to the antimitotic effects of Plk1 inhibition, leading to spindle assembly checkpoint-dependent mitotic cancer cell death and entosis. In a murine patient-derived xenograft model of abiraterone-resistant metastatic castration-resistant prostate cancer (mCRPC), combined onvansertib and abiraterone resulted in enhanced mitotic arrest and dramatic inhibition of tumor cell growth compared with either agent alone. Overall, this work establishes a mechanistic basis for the phase II clinical trial (NCT03414034) testing combined onvansertib and abiraterone in mCRPC patients and indicates this combination may have broad utility for cancer treatment.

SIGNIFICANCE

Abiraterone treatment induces mitotic defects that sensitize cancer cells to Plk1 inhibition, revealing an AR-independent mechanism for this synergistic combination that is applicable to a variety of cancer types.

Oncolytic Adenovirus, a New Treatment Strategy for Prostate Cancer

Prostate cancer is the most common cancer and one of the leading causes of cancer mortality in males. Androgen-deprivation therapy (ADT) is an effective strategy to inhibit tumour growth at early stages. However, 10~50% of cases are estimated to progress to metastatic castration-resistant prostate cancer (mCRPC) which currently lacks effective treatments. Clinically, salvage treatment measures, such as endocrine therapy and chemotherapy, are mostly used for advanced prostate cancer, but their clinical outcomes are not ideal. When the existing clinical therapeutic methods can no longer inhibit the development of advanced prostate cancer, human adenovirus (HAdV)-based gene therapy and viral therapy present promising effects. Pre-clinical studies have shown its powerful oncolytic effect, and clinical studies are ongoing to further verify its effect and safety in prostate cancer treatment. Targeting the prostate by HAdV alone or in combination with radiotherapy and chemotherapy sheds light on patients with castration-resistant and advanced prostate cancer. This review summarizes the advantages of oncolytic virus-mediated cancer therapy, strategies of HAdV modification, and existing preclinical and clinical investigations of HAdV-mediated gene therapy to further evaluate the potential of oncolytic adenovirus in prostate cancer treatment.

Real-world Treatment Sequencing in Patients with Metastatic Castration-resistant Prostate Cancer: Results from the Prospective, International, Observational Prostate Cancer Registry

Background

Prostate cancer has a multifaceted treatment pattern. Evidence is lacking for optimal treatment sequences for metastatic castration-resistant prostate cancer (mCRPC).

Objective

To increase the understanding of real-world treatment pathways and outcomes in patients with mCRPC.

Design, setting, and participants

A prospective, noninterventional, real-world analysis of 3003 patients with mCRPC in the Prostate Cancer Registry (PCR; NCT02236637) from June 14, 2013 to July 9, 2018 was conducted.

Intervention

Patients received first- and second-line hormonal treatment and chemotherapy as follows: abiraterone acetate plus prednisone (abiraterone)-docetaxel (ABI-DOCE), abiraterone-enzalutamide (ABI-ENZA), abiraterone–radium-223 (ABI-RAD), docetaxel-abiraterone (DOCE-ABI), docetaxel-cabazitaxel (DOCE-CABA), docetaxel-enzalutamide (DOCE-ENZA), and enzalutamide-docetaxel (ENZA-DOCE).

Outcome measurements and statistical analysis

Baseline patient characteristics, quality of life, mCRPC treatments, and efficacy outcomes (progression and survival) were presented descriptively.

Results and limitations

Data from 727 patients were eligible for the analysis (ABI-DOCE n = 178, ABI-ENZA n = 99, ABI-RAD n = 27, DOCE-ABI n = 191, DOCE-CABA n = 74, DOCE-ENZA n = 116, and ENZA-DOCE n = 42). Demographics and disease characteristics among patients between different sequences varied greatly. Most patients who started on abiraterone or enzalutamide stopped therapy because of disease progression. No randomisation to allow treatment/sequence comparisons limited this observational study.

Conclusions

The real-world PCR data complement clinical trial data, reflecting more highly selected patient populations than seen in routine clinical practice. Baseline characteristics play a role in mCRPC first-line treatment selection, but other factors, such as treatment availability, have an impact. Efficacy observations are limited and should be interpreted with caution.

Patient summary

Baseline characteristics appear to have a role in the first-line treatment selection of metastatic castration-resistant prostate cancer in the real-world setting. First-line abiraterone acetate plus prednisone seems to be the preferred treatment option for older patients and those with lower Gleason scores, first-line docetaxel for younger patients and those with more advanced disease, and first-line enzalutamide for patients with fewer metastases and more favourable performance status. The benefit to patients from these observations remains unknown.

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.

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.

Abiraterone, Orteronel, Enzalutamide and Docetaxel: Sequential or Combined Therapy?

Objective: To summarize the current therapeutic status using chemotherapeutic agent docetaxel and endocrine therapeutic agents (ARAT, abiraterone, orteronel or enzalutamide) for the treatment of metastatic castration-resistant prostate cancer (mCRPC), including sequential therapy and combined therapy, to promote the consensus on the optimal regimen for achieving superior treatment efficacy.

Methods: Through literature search in PubMed, articles with the following relevant keywords were collected and anlyzed: CRPC, abiraterone, orteronel and enzalutamide, median survival, overall survival, prostate specific antigen (PSA), PSA response rate and median radiologic progression-free survival.

Results: Fifty-eight articles were obtained and analyzed in this review. These articles included androgen axis-targeting agents after docetaxel, docetaxel after androgen axis-targeting agents, Triple sequential and combination therapy, covering four current drugs for mCRPC treatment: docetaxel, abiraterone, orteronel, and enzalutamide. It was found that there may be some cross-resistance between androgen axis-targeting agents, which will reduce the efficacy of subsequent drug treatment. Although neither of the studies of using combination therapy showed serious drug toxicity, the efficacy of sequential therapy was not as good as expected. Most adverse reactions after treatment were reported to be level 1–2.

Conclusion: Based on the results of the current studies, abiraterone followed by enzalutamide treatment is the best sequential treatment for most docetaxel-naïve patients. This treatment achieves not only good OS, but also PFS and PSA response rates. In addition, for patients who have previously failed docetaxel treatment, enzalutamide is the best choice as the subsequent treatment.

Sequencing of Systemic Therapies in the Management of Advanced Prostate Cancer in India: a Delphi-Based Consensus

INTRODUCTION

With the availability of an increasing number of therapeutic options for advanced prostate cancer (APC), optimal sequencing and combination of therapies have emerged to be the areas of challenges. In the Indian context, there is a dearth of consensus recommendations to guide clinicians regarding optimal sequencing of therapy in APC management. A Delphi-based consensus regarding optimal therapy sequencing in APC management was developed by an expert panel of medical oncologists from across India.

METHODS

An expert scientific committee of 11 medical oncologists and an expert panel of 53 medical oncologists from India constituted the panel for the Delphi consensus. In the first phase, a questionnaire with 41 clinical statements was developed in several critical controversial areas in APC treatment. In the second phase, 29 clinical statements were reworked and sent to eight experts to obtain their opinions on best practices. The consensus ratings were based on a 9-point Likert scale. Based on the overall response, statements with a mean score of ≥ 7 with 1 outlier were considered as "consensus."

RESULTS

Degarelix was the preferred androgen deprivation therapy (ADT). While ADT plus docetaxel was the preferred option for metastatic castrate-sensitive/naïve prostate cancer patients with high-volume disease, ADT with abiraterone was the preferred choice for low-volume disease. Docetaxel was the preferred first-line treatment option in men who received ADT alone in the castrate-sensitive/naïve setting. For patients progressing on or after docetaxel for metastatic castrate-resistant prostate cancer (without prior abiraterone or enzalutamide), the experts reached a consensus on the use of enzalutamide as the preferred second-line treatment option. No consensus was reached for the third-line treatment options.

CONCLUSION

This article is intended to serve as a guide to help clinicians discuss with their patients as part of the shared and multidisciplinary decision-making for improved APC management in India.

The iceberg plot, improving the visualisation of therapy response in oncology in the era of sequence-directed therapy

Modern clinical cancer research increasingly relies on the visual communication of complex response and treatment sequencing data. Graphical representations used in oncology currently fail to provide adequate information on any prior treatment(s) responses, focussing on current treatment effects in isolation. We have developed a new graphical illustration, the 'iceberg plot,' to allow improved comparison of prior treatment response with current therapy. To demonstrate the potential clinical utility of this new graphical representation, we have performed an independent reanalysis of a clinical study trialling sequence-directed therapy. In this example, prior therapy responses are contrasted with current treatment response, with further validation using the 'Von Hoff' criteria to assess for exceptional response. This example demonstrates the versatility and clinical utility of the 'iceberg plot,' showing what was previously hidden and provides improved visualisation of prior and current treatment responses together.

Current and Emerging Therapies for Metastatic Castration-Resistant Prostate Cancer (mCRPC)

Metastatic castration-resistant prostate cancer (mCRPC) encompasses a heterogeneous wide range of molecular tumor behavior and a high risk of progression. Early detection and treatment are therefore crucial in these patients. Treatment has improved drastically in recent years and many novel therapeutic agents are currently under investigation. However, due to the rapidly changing therapeutic landscape in mCRPC, it is difficult for clinicians to keep up to date with the latest innovations in this area. In the present narrative review, we discuss the current and emerging therapies for mCRPC as well as the clinical and molecular factors that can help predict which patients are most likely to benefit from these novel agents.

Optimal Sequencing and Predictive Biomarkers in Patients with Advanced Prostate Cancer

The treatment landscape of advanced prostate cancer has completely changed during the last decades. Chemotherapy (docetaxel, cabazitaxel), androgen-receptor signaling inhibitors (ARSi) (abiraterone acetate, enzalutamide), and radium-223 have revolutionized the management of metastatic castration-resistant prostate cancer (mCRPC). Lutetium-177-PSMA-617 is also going to become another treatment option for these patients. In addition, docetaxel, abiraterone acetate, apalutamide, enzalutamide, and radiotherapy to primary tumor have demonstrated the ability to significantly prolong the survival of patients with metastatic hormone-sensitive prostate cancer (mHSPC). Finally, apalutamide, enzalutamide, and darolutamide have recently provided impactful data in patients with nonmetastatic castration-resistant disease (nmCRPC). However, which is the best treatment sequence for patients with advanced prostate cancer? This comprehensive review aims at discussing the available literature data to identify the optimal sequencing approaches in patients with prostate cancer at different disease stages. Our work also highlights the potential impact of predictive biomarkers in treatment sequencing and exploring the role of specific agents (i.e., olaparib, rucaparib, talazoparib, niraparib, and ipatasertib) in biomarker-selected populations of patients with prostate cancer (i.e., those harboring alterations in DNA damage and response genes or PTEN).

Predicting toxicity-related docetaxel discontinuation and overall survival in metastatic castration-resistant prostate cancer: a pooled analysis of open phase 3 clinical trial data

BACKGROUND

Docetaxel is widely used in metastatic castration-resistant prostate cancer (mCRPC), however its optimal use remains unclear in the current treatment landscape. Biomarkers to predict Docetaxel toxicity may help optimize treatment selection. We aimed to create a predictive model for toxicity-related Docetaxel discontinuation (TRDD).

METHODS

Through Project Data Sphere, we accessed individual patient data from the control arms of three frontline mCRPC trials: ASCENT2, VENICE, and MAINSAIL. The inclusion criteria for these trials were all similar and included patients with chemotherapy-naïve mCRPC. The primary outcome was occurrence of TRDD. A competing risks regression (CRR) was used to predict TRDD, after accounting for the occurrence of competing events (death or progression). The output of the model was used as the dependent variable on a classification and regression tree (CART) to identify risk groups for TRDD.

RESULTS

Overall, 1568 patients were considered. Pooled CI of TRDD was 19% after accounting for competing events (death: 474; progression: 59) within 12 months of starting treatment. To build a risk calculator we relied on a CRR that ultimately included age, ECOG performance status, AST, bilirubin, use of analgesics, and presence of diabetes and chronic kidney disease. The CART analysis identified three risk groups that were named: low (model-derived TRDD risk ≤24%), intermediate (25-64%), and high (≥65%) risk group. In each risk group, probability of TRDD during treatment was 14%, 58%, and 79%, and median OS was 24 months, 20 months, and 13 months, respectively (p < 0.001).

CONCLUSIONS

Treatment selection in mCRPC remains a challenge. Our model can help clinicians balance Docetaxel toxicity and efficacy. The three risk categories that we identified correlated with OS and this is particularly useful for an optimal shared decision-making process.

Genetic testing for homologous recombination repair (HRR) in metastatic castration-resistant prostate cancer (mCRPC): challenges and solutions

Patients with metastatic castration-resistant prostate cancer (mCRPC) have an average survival of only 13 months. Identification of novel predictive and actionable biomarkers in the homologous recombination repair (HRR) pathway in up to a quarter of patients with mCRPC has led to the approval of targeted therapies like poly-ADP ribose polymerase inhibitors (PARPi), with the potential to improve survival outcomes. The approval of PARPi has led to guideline bodies such as the National Comprehensive Cancer Network (NCCN) to actively recommend germline and or somatic HRR gene panel testing to identify patients who will benefit from PARPi. However, there are several challenges as genetic testing is still at an early stage especially in low- and middle-income countries, with cost and availability being major impediments. In addition, there are issues such as choice of optimal tissue for genetic testing, archival, storage, retrieval of tissue blocks, interpretation and classification of variants in the HRR pathway, and the need for pretest and post-test genetic counseling. This review provides insights into the HRR gene mutations prevalent in mCRPC and the challenges for a more widespread gene testing to identify actionable germline pathogenic variants and somatic mutations in the HRR pathway, and proposes a clinical algorithm to enhance the efficiency of the gene testing process.

Cross-resistance and drug sequence in prostate cancer

The treatment landscape of advanced prostate cancer has widely expanded over the past years with androgen receptor signaling inhibitors (ARSIs) and taxane chemotherapy moving to earlier disease stages in the treatment of prostate cancer. With the increasing use of ARSIs in earlier disease stages, cross-resistance between treatments has emerged, which is a dominant impediment in current clinical practice. To overcome cross-resistance in the treatment of prostate cancer, it is of paramount importance to decipher the mechanisms of cross-resistance between ARSIs and between ARSIs and chemotherapy. Here, molecular mechanisms of resistance to the available therapies including androgen receptor (AR) splice variants, AR overexpression, AR mutations and glucocorticoid receptor upregulation are described. Based on these underlying mechanisms, clinical data of cross-resistance between ARSIs and chemotherapy have been reported. Only recently these data have been confirmed in prospective randomized trials. From these studies, it has become clear that sequential ARSI treatment has no place in the treatment of advanced prostate cancer due to emerging drug resistance. In addition, based on prospective evidence, we argue that it is worth considering an early switch to cabazitaxel treatment in case of lack of benefit on docetaxel regimen after an ARSI treatment. Based on these new insights from randomized trials, several recommendations for treatment sequence are proposed.

Novel Strategies for Treating Castration-Resistant Prostate Cancer

The development of castration resistance is an inevitable pathway for the vast majority of patients with advanced prostate cancer. Recently, there have been significant breakthroughs in the understanding and management options of castration-resistant prostate cancer. Three novel hormonal agents showed survival benefits in non-metastatic patients. As for metastatic disease, there was an even wider range of management options being investigated. This review summarized advances in the management of castration-resistant prostate cancer (CRPC) including emerging data on novel imaging techniques and treatment strategies.

Current Status and Future Perspectives of Androgen Receptor Inhibition Therapy for Prostate Cancer: A Comprehensive Review

The androgen receptor (AR) is one of the main components in the development and progression of prostate cancer (PCa), and treatment strategies are mostly directed toward manipulation of the AR pathway. In the metastatic setting, androgen deprivation therapy (ADT) is the foundation of treatment in patients with hormone-sensitive prostate cancer (HSPC). However, treatment response is short-lived, and the majority of patients ultimately progress to castration-resistant prostate cancer (CRPC). Surmountable data from clinical trials have shown that the maintenance of AR signaling in the castration environment is accountable for disease progression. Study results indicate multiple factors and survival pathways involved in PCa. Based on these findings, the alternative molecular pathways involved in PCa progression can be manipulated to improve current regimens and develop novel treatment modalities in the management of CRPC. In this review, the interaction between AR signaling and other molecular pathways involved in tumor pathogenesis and its clinical implications in metastasis and advanced disease will be discussed, along with a thorough overview of current and ongoing novel treatments for AR signaling inhibition.

Real-World Outcomes in First-Line Treatment of Metastatic Castration-Resistant Prostate Cancer: The Prostate Cancer Registry

BACKGROUND

Metastatic prostate cancer has a 30% 5-year survival rate despite recent therapeutic advances. There is a need to improve the clinical understanding and treatment of this disease, particularly in the real-world setting and among patients who are under-represented in clinical trials.

OBJECTIVE

We aimed to evaluate the characteristics and clinical outcomes of patients who received their first treatment for metastatic castration-resistant prostate cancer (mCRPC) in routine clinical practice, independent of treatment used, including subgroups with baseline cardiac disease, diabetes mellitus, or visceral metastases.

PATIENTS AND METHODS

Prospective, noninterventional analysis of patient record data in the multicenter Prostate Cancer Registry (PCR) of men with mCRPC. The data were collected in 16 countries with the aim of recruiting more than 3000 patients between 2013 and 2016. The study end date was 9 July 2018. Data evaluated included baseline characteristics, treatment exposure, and efficacy outcomes [overall survival (OS) and time to progression (TTP)] of patients treated with abiraterone acetate plus prednisone or prednisolone (collectively, "abiraterone"), enzalutamide, or docetaxel. Descriptive outcomes are reported from the overall patient population and subgroups of patients with baseline cardiovascular disease, diabetes mellitus, or visceral metastases. The treatment effects for time to progression were compared for the overall patient population.

RESULTS

The study enrollment period lasted 2.5 years, and each patient was followed for a maximum of 3 years. A total of 1874 patients in the PCR had not received previous mCRPC treatment at baseline, although they had received androgen-deprivation therapy. Prevalent co-morbidities included cardiovascular disease in 65.4% and diabetes mellitus in 17.4% of patients. Baseline characteristics suggested that patients with more advanced disease received docetaxel treatment. In the overall patient population, the median time to progression with abiraterone, enzalutamide, and docetaxel as first-line mCRPC therapy was 9.6, 10.3, and 7.6 months, respectively, and median OS was 27.1, 27.1, and 27.9 months, respectively. Outcomes in the subgroups of patients with cardiovascular disease or diabetes mellitus were similar to those of the whole population in the analysis. As expected, patients with visceral metastases had shorter TTP and OS than patients in the overall population.

CONCLUSIONS

This analysis shows, for the first time, the effectiveness in parallel of first-line abiraterone, enzalutamide, and docetaxel in mCRPC, including in patients with co-morbidities such as cardiovascular disease or diabetes mellitus or in patients with visceral metastases. These real-world findings from the PCR provide meaningful information to help manage mCRPC, particularly in patients under-represented in clinical studies.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT02236637; registered September 2014.

Overall Survival Among Chemotherapy-Naive Patients With Castration-Resistant Prostate Cancer Under Abiraterone Versus Enzalutamide: A Direct Comparison Based on a 2014-2018 French Population Study (the SPEAR Cohort)

Abiraterone acetate (ABI) and enzalutamide (ENZ) are considered to be clinically relevant comparators among chemotherapy-naive patients with castration-resistant prostate cancer. No clinical trials comparing overall survival with ABI versus ENZ in a head-to-head approach have been published so far. A few observational studies with low power suggested a potential benefit of ENZ. We used the French National Health Data System to compare overall survival of new users of ABI and ENZ among chemotherapy-naive patients with castration-resistant prostate cancer in 2014-2017, followed through 2018 (the SPEAR cohort, a 2014-2018 cohort study). With an intent-to-treat approach, a survival analysis was performed, estimating hazard ratios for overall survival with the inverse probability weighted Cox model method. Among 10,308 new users, 64% were treated with ABI and 36% with ENZ. The crude mortality rate was 25.2 per 100 person-years (95% confidence interval (CI): 24.4, 26.0) for ABI and 23.7 per 100 person-years (95% CI: 22.6, 24.9) for ENZ. In the weighted analysis, ENZ was associated with better overall survival compared with ABI (hazard ratio = 0.90 (95% CI: 0.85, 0.96) with a median overall survival of 31.7 months for ABI and 34.2 months for ENZ). When restricting to 2015-2017 new users, the effect estimate shifted up to a hazard ratio of 0.93 (95% CI: 0.86, 1.01).

Regulation of carcinogenesis and mediation through Wnt/β-catenin signaling by 3,3'-diindolylmethane in an enzalutamide-resistant prostate cancer cell line

Enzalutamide (ENZ) is an important drug used to treat castration-resistant prostate cancer (CRPC), which inhibits androgen receptor (AR) signaling. Previous study showed that 3,3′-diindolylmethane (DIM) is an AR antagonist that also inhibits Wnt signaling and epithelial-mesenchymal transition (EMT). To investigate whether combined treatment with ENZ and DIM can overcome ENZ resistance by regulating Wnt signaling to inhibit AR signaling and EMT in ENZ-resistant prostate cancer cells, 22Rv1 cells were cultured in normal medium and treated with ENZ, DIM, and DIM with ENZ. Exposure of ENZ-resistant cells to both DIM and ENZ significantly inhibited cell proliferation without cytotoxicity and invasion in comparison with the control. DIM significantly increased the E-cadherin expression and inhibited the expressions of Vimentin and Fibronectin, subsequently inhibiting EMT. Co-treatment with ENZ and DIM significantly increased the expressions of GSK3β and APC and decreased the β-catenin protein expression, causing inhibition of Wnt signaling and AR expression, it also significantly decreased the AR-v7 expression and down-regulated AR signaling. Via suppression of Wnt and AR signaling, co-treatment increased the E-cadherin and decreased the Vimentin and Fibronectin RNA and protein expressions, then inhibited EMT. Co-treatment with DIM and ENZ regulated Wnt signaling to reduce not only the AR expression, but also the AR-v7 expression, indicating suppression of EMT that inhibits cancer cell proliferation, invasion and migration to ameliorate ENZ resistance.

Interactions between androgen receptor signaling and other molecular pathways in prostate cancer progression: Current and future clinical implications

In last years several improvements have been made in the management of prostate cancer (PCa). Androgen receptor (AR) is considered the main driver in PCa growth and progression and most drugs are directed against AR pathway. Once PCa spreads outside the prostate, androgen deprivation therapy (ADT) represents the cornerstone of treatment in hormone-sensitive prostate cancer (HSPC). Unfortunately, the response is only transient and most patients eventually develop castration-resistant prostate cancer (CRPC). Most resistance mechanisms depend on maintenance of AR signalling in castration environment. Recent discoveries of multiple growth-promoting and survival pathways in PCa suggest the importance of alternative mechanisms involved in disease progression, such as DNA damage response pathway, PTEN/PI3K/AKT/mTOR pathway, cell cycle pathway, WNT pathway, TMPRSS2/ETS fusion, neuroendocrine pattern and immune system response. In this review, we discuss the interplay between AR signaling and other molecular pathways involved in PCa pathogenesis and their therapeutic implication in advanced disease.

Antitumour activity of TH1579, a novel MTH1 inhibitor, against castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) treatment still remains difficult. The aim of the present study was to determine the antitumour efficacy of the MutT homolog 1 (MTH1) inhibitor, TH1579, against castration-resistant prostate cancer. PC-3 and DU-145 prostate cancer cells were treated with different concentrations of TH1579. C4-2 cells with or without androgen receptor (AR) were also treated with TH1579 to assess AR function. Cell survival, 8-oxo-dG levels and DNA damage were measured using cell viability assays, western blotting, immunofluorescence analysis and flow cytometry. TH1579 inhibited CRPC cell proliferation in a dose-dependent manner. The viabilities of PC-3 and DU-145 cells treated with 1 µM of TH1579 were 28.6 and 24.1%, respectively. The viabilities of C4-2 cells with and without AR treated with 1 µM TH1579 were 10.6 and 19.0%, respectively. Moreover, TH1579 treatment increased 8-oxo-dG levels, as well as the number of 53BP1 and γH2A.X foci, resulting in increased DNA double-strand breakage and apoptosis in PC-3 and DU-145 cells. The findings of the present study demonstrated that TH1579 exerted strong antitumour effects on CRPC cells, and may therefore be used as a potential therapeutic agent for the clinical treatment of CRPC.

The clinical benefit of sequential therapy with androgen receptor axis-targeted agents alone in patients with castration-resistant prostate cancer: A propensity score-matched comparison study

BACKGROUND

The optimal sequential therapy for castration-resistant prostate cancer (CRPC) remains unknown. In recent years, some doubts have emerged regarding the clinical benefit of sequential therapy with androgen receptor axis-targeted agents (ART) such as abiraterone (ABI) or enzalutamide (ENZ) for patients with CRPC. We compared the effect of ART-to-ART (AA) sequential therapy after castration resistance with that of docetaxel (DTX)-combined sequential therapy (ART to DTX or DTX to ART) in patients with CRPC.

METHODS

We retrospectively identified and analyzed the data of 315 patients with CRPC treated in our seven affiliated institutions between 2009 and 2019. All patients received either DTX or ART (ABI or ENZ) as the first- or second-line therapy after castration resistance. We compared the overall survival (OS) and the second progression-free survival (PFS2), calculated from the initiation of first-line therapy after castration resistance, between the AA sequence group and the DTX-combined sequence group. PFS2 was defined as the period from the start of first-line treatment after castration resistance to progression on second-line treatment. To minimize selection bias from possible confounders, we performed propensity score matching using one-to-one nearest neighbor matching without replacement.

RESULTS

Overall, 106 and 209 patients were administered the AA sequential therapy and DTX-combined sequential therapy, respectively. The clinicopathological variables of patients were well balanced after propensity score matching, and there were no significant differences between the two groups. In the propensity score-matched cohort, OS was not significantly different between the two groups (median, 37.9 vs. 45.4 months; hazard ratio [HR], 1.10; 95% confidence interval [CI], 0.68-1.79; p = .701), while PFS2 was significantly shorter in the AA group than in the DTX-combined group (median, 12.9 vs. 21.6 months; HR, 1.70; 95% CI, 1.16-2.48; p = .007).

CONCLUSIONS

Certain patients with CRPC can benefit from ART-to-ART sequential therapy in a daily clinical setting.

Clinical implications of genomic evaluations for prostate cancer risk stratification, screening, and treatment: a narrative review

New classification systems based on molecular features have been introduced to improve precision medicine for prostate cancer (PCa). This review covers the increasing risk of PCa and the differences in response to targeted therapy that are related to specific gene variations. We believe that genomic evaluations will be useful for guiding PCa risk stratification, screening, and treatment. We searched the PubMed and MEDLINE databases for articles related to genomic testing for PCa that were published in 2020 or earlier. There is increasing evidence that germline mutations in DNA repair genes, such as BRCA1/2 or ATM, are closely related to the development and aggressiveness of PCa. Targeted prostate-specific antigen screening based on the presence of germline alterations in DNA repair genes is recommend to achieve an early diagnosis of PCa. In cases of localized PCa, even if it has a favorable risk classification, patients under active surveillance with these gene alterations are likely to develop aggressive PCa. Thus, active treatment may be preferable to active surveillance for these patients. In cases of metastatic castration–resistant PCa, BRCA1/2 and DNA mismatch repair genes may be useful biomarkers for predicting the response to androgen receptor–targeting agents, poly (ADP-ribose) polymerase inhibitors, platinum chemotherapy, prostate-specific membrane antigen–targeted therapy, immunotherapy, and radium-223. Genomic evaluations may allow for risk stratification of patients with PCa based on their molecular features, which may help guide precision medicine for treating PCa.

Effect of Baseline Characteristics on Cabazitaxel Treatment Duration in Patients with Metastatic Castration-Resistant Prostate Cancer: A Post Hoc Analysis of the Compassionate Use/Expanded Access Programs and CAPRISTANA Registry

We examined factors that may impact cabazitaxel treatment duration in a real-life setting in a compassionate use program, expanded access program, and prospective observational study in metastatic castration-resistant prostate cancer (mCRPC). Patients with mCRPC previously treated with docetaxel (N = 1,621) received cabazitaxel 25 mg/m² intravenously every 3 weeks until disease progression, death, unacceptable toxicity or physician/patient decision. The median number of cabazitaxel cycles was six (range, 1-49); 708 patients (43.7%) received >6 cycles. Patients receiving >6 cycles tended to have a better Eastern Cooperative Oncology Group performance status of 0-1 (p = 0.0017 for ≤6 vs. >6 cycles). Overall, 348 patients (21.5%) were ≥75 years of age; 139 (39.9%) received >6 cycles. The main reason for discontinuation was disease progression; however, in patients receiving 1-2 cycles, the main reason for discontinuation was adverse events. Only 52 patients (3.2%) progressed during cycles 1-2. Cabazitaxel was well tolerated in these studies, which included some elderly and frail patients, offering clinicians an important treatment option in the management of mCRPC. Proactive management of adverse events may allow patients to receive a higher number of cabazitaxel cycles and derive greater benefit.

Self-assembly of amphiphilic phospholipid peptide dendrimer-based nanovectors for effective delivery of siRNA therapeutics in prostate cancer therapy

RNA interference (RNAi) holds great promise for therapeutic applications. However, safe and successful clinical translation essentially requires further advancement of developing efficient delivery systems. Herein, we report that amphiphilic phospholipid peptide dendrimers (AmPPDs) could mediated effective delivery of siRNA targeting Hsp27 for treating castration-resistant prostate cancer (CRPC). AmPPDs bears natural lipid derivative DSPE as the hydrophobic tail and different dendritic l-lysine as the hydrophilic head, capable of compacting siRNA into nanoparticles to protect it from enzymatic degradation. Interestingly, DSPE-KK₂, AmPPD bearing smaller hydrophilic dendron, promoting more efficient intracellular uptake and endosome release of the so-formed siRNA complexes, as well as better siRNA releasing ability, ultimately resulting in more potent gene silencing and anticancer effects both in vitro and in vivo. Such outstanding performance of DSPE-KK₂ in siRNA delivery may attribute to its optimal balance between the hydrophobic tail and hydrophilic dendritic portion. Our findings provide guidance for the development of safe and effective dendrimer-based siRNA delivery system, thus bringing new hope for combating various diseases.

Comparison of Oncologic Outcomes Between Two Alternative Sequences with Abiraterone Acetate and Enzalutamide in Patients with Metastatic Castration-Resistant Prostate Cancer: A Systematic Review and Meta-Analysis

Sequential treatment of androgen receptor axis targeted agents (ARAT), abiraterone acetate (ABI) and enzalutamide (ENZA), in metastatic castration-resistant prostate cancer (mCRPC) demonstrated some positive effects, but cross-resistances between ABI and ENZA that reduce activity have been suggested. Therefore, we conducted a meta-analysis to compare oncologic outcomes between the treatment sequences of ABI-ENZA and ENZA-ABI in patients with mCRPC. The primary endpoint was a combined progression-free survival (PFS), and the secondary endpoint was overall survival (OS). A total of five trials on 553 patients were included in this study. Each of the included studies was retrospective. In two studies including both chemo-naïve and post-chemotherapy mCRPC patients, for ABI-ENZA compared with ENZA-ABI, pooled hazard ratios (HRs) for PFS and OS were 0.37 (p < 0.0001; 95% confidence intervals (CIs), 0.23–0.60) and 0.64 (p = 0.10; 95% CIs, 0.37–1.10), respectively. In three studies with chemo-naïve mCRPC patients only, for ABI-ENZA compared with ENZA-ABI, pooled HRs for PFS and OS were 0.57 (p = 0.02; 95% CIs, 0.35–0.92) and 0.86 (p = 0.39; 95% CIs, 0.61–1.21), respectively. The current meta-analysis revealed that ABI-ENZA had a significantly more favorable oncological outcome, but the level of evidence was low. Therefore, large-scale randomized trials may be needed.

Metastatic Castration-Resistant Prostate Cancer Previously Treated With Docetaxel-Based Chemotherapy: Treatment Patterns From the PROXIMA Prospective Registry

Purpose

There is a major clinical need to devise an optimal treatment sequence for the multiple therapy options available for patients with metastatic castration-resistant prostate cancer (mCRPC). In the absence of prospective clinical trials, sequencing information can be derived from large, real-world registry studies.

Patients and Methods

PROXIMA (Treatment Patterns in Patients With Metastatic Castration-Resistant Prostate Cancer Previously Treated With Docetaxel-Based Chemotherapy) is a large, global, prospective registry study evaluating real-world treatment patterns of patients with mCRPC who experience disease progression during or after docetaxel therapy. Patients were enrolled worldwide between 2011 and 2014. Treatments were determined by the treating physicians and recorded in categories of chemotherapy, hormonal therapy, targeted therapy, immunotherapy, and palliative therapy. Treatment sequencing patterns, response to treatment, and types of progression were recorded and analyzed. Progression-free survival and overall survival with different treatment modalities were analyzed using Kaplan–Meier method.

Results

Treatment patterns were evaluated in 903 patients. Therapy selection was influenced by region. Hormonal therapy (57.5%) and taxane chemotherapy (26.4%) were the most frequently administered first subsequent treatments after docetaxel. Tumor responses to first subsequent treatment were observed in 22.6% of evaluable patients. Overall survival and progression-free survival did not differ significantly across different treatment modalities.

Conclusion

Identifying an optimal treatment sequence is vital for improving the care of patients with mCRPC. The PROXIMA registry provided a representative sample of global data on real-world treatment patterns for patients with mCRPC previously treated with docetaxel. These data can be used to devise optimal therapy sequences and inform treatment decisions.

Androgen Receptor Modulation Optimized for Response-Splice Variant: A Phase 3, Randomized Trial of Galeterone Versus Enzalutamide in Androgen Receptor Splice Variant-7-expressing Metastatic Castration-resistant Prostate Cancer

BACKGROUND

Detection of androgen receptor (AR) splice variant-7 (AR-V7) messenger RNA (mRNA) in circulating tumor cells (CTCs) is associated with a suboptimal response to abiraterone and enzalutamide in metastatic castration-resistant prostate cancer (mCRPC). Galeterone inhibits CYP17 and AR, and induces AR protein degradation. We hypothesized that galeterone would be clinically superior to enzalutamide in AR-V7-positive (AR-V7+) mCRPC.

OBJECTIVE

To screen and characterize AR-V7+ mCRPC, and evaluate galeterone compared with enzalutamide.

DESIGN, SETTING, AND PARTICIPANTS

This was a multicenter randomized phase 3 trial; enzalutamide-, abiraterone-, and chemotherapy-naïve mCRPC patients had AR-V7 prescreening using a CTC-based mRNA assay.

INTERVENTION

AR-V7+ patients were randomized (1:1) to open-label galeterone or enzalutamide; planned sample size was 148.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was radiographic progression-free survival (rPFS). Baseline AR-V7 status was correlated with patient characteristics.

RESULTS AND LIMITATIONS

Overall, 953 men were prescreened for AR-V7; 323 (34%) had detectable CTCs, and 73/323 had AR-V7 mRNA. The AR-V7+ prevalence was 8% (73/953; 95% confidence interval [CI] 6-10%). AR-V7 was associated with indicators of advanced and high-volume disease at baseline, including higher prostate-specific antigen (PSA) level (p < 0.001), more bone metastases (p < 0.001), docetaxel for hormone-sensitive disease (p < 0.001), prior first-generation androgen deprivation therapy (p < 0.001), and shorter time from diagnosis to enrollment (p < 0.001). Of 73 eligible patients, 38 were randomized to galeterone (n=19) or enzalutamide (n=19); 35 dropped out before randomization. Owing to high censorship for the rPFS events, the data monitoring committee recommended early closure based on interim evidence that the primary endpoint would not be met. The PSA50 values were 2/16 (13%) and 8/19 (42%) for galeterone and enzalutamide respectively (proportion difference=-0.278, 95% CI -0.490 to 0.097).

CONCLUSIONS

The prevalence of CTC mRNA AR-V7 in first-line mCRPC was 8% (95% CI 6-10%). AR-V7+ was associated with the characteristics of aggressive and advanced disease. These men had rapid disease progression. Development of galeterone will not be pursued.

PATIENT SUMMARY

Of men with metastatic castration-resistant prostate cancer, 8% had the androgen receptor splice variant-7 (AR-V7) blood biomarker. The AR-V7+ patients had features of aggressive disease. Thirty-eight men were treated with either galeterone or enzalutamide; the trial was stopped early prior to determining efficacy because too many patients transitioned off the trial due to advancing cancer before having required radiographs.

Circulating Tumor Cell-Based Molecular Classifier for Predicting Resistance to Abiraterone and Enzalutamide in Metastatic Castration-Resistant Prostate Cancer

While circulating tumor cell (CTC)-based detection of AR-V7 has been demonstrated to predict patient response to second-generation androgen receptor therapies, the rarity of AR-V7 expression in metastatic castrate-resistant prostate cancer (mCRPC) suggests that other drivers of resistance exist. We sought to use a multiplex gene expression platform to interrogate CTCs and identify potential markers of resistance to abiraterone and enzalutamide. 37 patients with mCRPC initiating treatment with enzalutamide (n = 16) or abiraterone (n = 21) were prospectively enrolled for CTC collection and gene expression analysis using a panel of 89 prostate cancer-related genes. Gene expression from CTCs was correlated with PSA response and radioclinical progression-free survival (PFS) using Kaplan-Meier and Cox regression analyses. Twenty patients (54%) had detectable CTCs. At a median follow-up of 11.3 months, increased expression of the following genes was significantly associated with shorter PSA PFS and radioclinical PFS: AR, AR-V7, PSA, PSCA, TSPAN8, NKX3.1, and WNT5B. Additionally, high SPINK1 expression was associated with increased PFS. A predictive model including all eight genes gave an area under the curve (AUC) of 0.84 for PSA PFS and 0.86 for radioclinical PFS. In comparison, the AR-V7 only model resulted in AUC values of 0.65 and 0.64.These data demonstrate that clinically relevant information regarding gene expression can be obtained from whole blood using a CTC-based approach. Multigene classifiers in this setting may allow for the development of noninvasive predictive biomarkers to guide clinical management.

Enzalutamide: A Review in Castration-Resistant Prostate Cancer

Oral enzalutamide (Xtandi^®), a second generation androgen receptor inhibitor, is indicated for the treatment of castration-resistant prostate cancer (CRPC) in numerous countries worldwide, with specific indications in this patient population varying between individual countries. Based on extensive experience in the clinical trial and/or real-world settings, oral enzalutamide 160 mg once daily is an effective and generally well tolerated treatment in a broad spectrum of patients with CRPC, including in nonmetastatic and metastatic disease and in chemotherapy-naive and -experienced metastatic CRPC. Enzalutamide is an emerging option for the treatment of men with nonmetastatic CRPC who are at high-risk for developing metastatic disease, and remains an important first-line option in chemotherapy-naive or -experienced patients with metastatic CRPC.

Identification of Novel Biomarkers of Homologous Recombination Defect in DNA Repair to Predict Sensitivity of Prostate Cancer Cells to PARP-Inhibitors

One of the most common malignancies in men is prostate cancer, for which androgen deprivation is the standard therapy. However, prostate cancer cells become insensitive to anti-androgen treatment and proceed to a castration-resistant state with limited therapeutic options. Therefore, besides the androgen deprivation approach, novel biomarkers are urgently required for specific targeting in this deadly disease. Recently, germline or somatic mutations in the homologous recombination (HR) DNA repair genes have been identified in at least 20–25% of metastatic castration-resistant prostate cancers (mCRPC). Defects in genes involved in HR DNA repair can sensitize cancer cells to poly(ADP-ribose) polymerase (PARP) inhibitors, a class of drugs already approved by the Food and Drug Administration (FDA) for breast and ovarian cancer carrying germline mutations in BRCA1/2 genes. For advanced prostate cancer carrying Breast cancer1/2 (BRCA1/2) or ataxia telengiectasia mutated (ATM) mutations, preclinical studies and clinical trials support the use of PARP-inhibitors, which received breakthrough therapy designation by the FDA. Based on these assumptions, several trials including DNA damage response and repair (DDR) targeting have been launched and are ongoing for prostate cancer. Here, we review the state-of-the-art potential biomarkers that could be predictive of cancer cell synthetic lethality with PARP inhibitors. The identification of key molecules that are affected in prostate cancer could be assayed in future clinical studies to better stratify prostate cancer patients who might benefit from target therapy.

Radium-223 for the treatment of bone metastases in castration-resistant prostate cancer: when and why

Radium-223 dichloride (²²³Ra) is the first, recently approved, α-particle-emitting radiopharmaceutical for the treatment of patients with bone metastases in castration-resistant prostate cancer (CRPC) and no evidence of visceral metastases. We explored MEDLINE, relevant congresses, and websites for data on ²²³Ra and prostate cancer therapies, focusing on therapeutic strategies and timing, bone metastases, and diagnostic assessment. ²²³Ra represents the only bone-targeting agent that has significantly extended patients' overall survival while reducing pain and symptomatic skeletal events. Unlike other radiopharmaceuticals, such as strontium-89 and samarium-153 EDTMP, ²²³Ra (11.4-days half-life) has shown a high biological efficiency mainly due to its short penetration range. These features potentially allow reduced bone marrow toxicity and limit undue exposure. ²²³Ra has been validated under the product name Xofigo^® by the US Food and Drug Administration and the European Medicines Agency. Patient selection, management, and treatment sequencing is recommended to be discussed in the context of a multidisciplinary environment, including oncology, urology, nuclear medicine, and radiation therapy physicians. No consensus has been achieved regarding the optimal timing and its administration as single agent or in combination with zoledronic acid or chemotherapy, so far. This review aims to provide a rationale for the use of ²²³Ra in treating metastases from CRPC, highlighting the crucial role of a multidisciplinary approach, the disputed inclusion and exclusion criteria on the basis of agencies regulations, and the value of diagnostics for therapy assessment.

HTA and innovative treatments evaluation: the case of metastatic castration-resistant prostate cancer

Purpose: To investigate the implications of the introduction of two hormonal therapies, abiraterone acetate + prednisone (AA+P) and enzalutamide (ENZA), for the treatment of naïve patients with metastatic castration-resistant prostate cancer (mCRPC) in the Italian setting.

Methods: In 2017–2018, a Health Technology Assessment was conducted in Italy, considering the National Healthcare Service (NHS) perspective. Data were retrieved from literature evidence, economic evaluations, and qualitative questionnaires, considering the 9 EUnetHTA dimensions, and a final multi-criteria approach.

Results: On the basis of mCRPC prevalence and incidence rates in Italy, the analysis considered 11,212 males eligible to either AA+P or ENZA treatments. Both drugs led to an improvement of the patients' overall survival, with respect to the standard of care, composed of docetaxel chemotherapy. However, AA+P showed a higher rate of drug-related moderate adverse events and a monitoring activities incidence superior to ENZA (+70%, p-value=0.00), which led to a major resources absorption (€ 1,056.02 vs € 316.25, p-value=0.00), whereas ENZA showed a better cost-effectiveness average value (CEV: 54,586.12 vs 57,624.15). Economic savings ranging from 1.46% to 1.61% emerged for the NHS, as well as organizational advantages, with fewer minutes required for the mCRPC management (AA+P: 815 mins vs ENZA: 500 mins). According to experts’ perceptions, based on a 7-item Likert scale (ranging from −3 to +3), similar results emerged on ethical and social impact (ENZA: 1.35 vs AA+P: 1.48, p-value>0.05), and on legal dimension (ENZA: 0.67 vs AA+P: 0.67, p-value>0.05), since both drugs improved the patients’ quality of life and received approval for use. High-level perceptions related to ENZA adoption emerged with regard to equity (ENZA: 0.69 vs AA+P: 0.25, p-value<0.05), since it is cortisone-free. Multi-criteria approach analysis highlighted a higher score of ENZA than comparator (0.79 vs 0.60, p-value=0.00).

Conclusion: The evidence-based information underlined the advantages of ENZA and AA+P treatments as therapeutic options for mCRPC patients. In the appraisal phase, the higher score than the comparator suggested ENZA as the preferred treatment for mCRPC.

IRE1α-XBP1s pathway promotes prostate cancer by activating c-MYC signaling

Activation of endoplasmic reticulum (ER) stress/the unfolded protein response (UPR) has been linked to cancer, but the molecular mechanisms are poorly understood and there is a paucity of reagents to translate this for cancer therapy. Here, we report that an IRE1α RNase-specific inhibitor, MKC8866, strongly inhibits prostate cancer (PCa) tumor growth as monotherapy in multiple preclinical models in mice and shows synergistic antitumor effects with current PCa drugs. Interestingly, global transcriptomic analysis reveal that IRE1α-XBP1s pathway activity is required for c-MYC signaling, one of the most highly activated oncogenic pathways in PCa. XBP1s is necessary for optimal c-MYC mRNA and protein expression, establishing, for the first time, a direct link between UPR and oncogene activation. In addition, an XBP1-specific gene expression signature is strongly associated with PCa prognosis. Our data establish IRE1α-XBP1s signaling as a central pathway in PCa and indicate that its targeting may offer novel treatment strategies.

Three-year interim results of overall and progression-free survival in a cohort of patients with prostate cancer (GESCAP group)

AIMS

To describe the 3-year progression-free survival (PFS), overall survival (OS) and disease-specific mortality in the prospective prostate cancer GESCAP cohort, as well as the progression to castration resistance in patients on hormone therapy.

MATERIAL AND METHODS

Prospective, observational, epidemiological, multicentre study. Of the 4087 patients recruited, 3843 were evaluable. The variables analysed were the risk group (localized, locally advanced, lymph involvement, metastatic), age, prostate-specific antigen (PSA) levels, Gleason score and initial treatment. Kaplan Meier survival analysis, the log-rank test and the Cox model were used to evaluate the survival data.

RESULTS

Three-year PFS was 81.4% and OS was 92.4%. During the 3 years of follow-up, 303 patients died (7.9%), 110 of them (36.3%) due to disease-related causes. The probability of castration resistance for all patients on hormone therapy (n=715) was 14.2%: 5%, 9.9%, 26.1% and 44.4% in localized, locally advanced, lymph involvement and metastatic cancer, respectively (log-rank P<.0001). Patients with metastases had poorer outcomes with respect to PFS, OS, disease-specific mortality and castration resistance. In the multivariate analysis, the Gleason score, PSA and presence of metastases were associated with shorter OS and PFS.

CONCLUSIONS

Our study showed stratification of risk, with a more unfavourable prognosis for patients with metastases. Patients with locally advanced disease differed with respect to those with localized disease due to their higher risk as regards disease-specific mortality. (Controlled-trials.com ISRCTN19893319).

Metastatic prostate cancer remains incurable, why?

Metastatic prostate cancer patients present in two ways-with already disseminated disease at the time of presentation or with disease recurrence after definitive local therapy. Androgen deprivation therapy is given as the most effective initial treatment to patients. However, after the initial response, almost all patients will eventually progress despite the low levels of testosterone. Disease at this stage is termed castration resistant prostate cancer (CRPC). Before 2010, the taxane docetaxel was the first and only life prolonging agent for metastatic CRPC (mCRPC). The last decade has witnessed robust progress in CRPC therapeutics development. Abiraterone, enzalutamide, apalutamide and sipuleucel-T have been evaluated as first- and second-line agents in mCRPC patients, while cabazitaxel was approved as a second-line treatment. Radium-223 dichloride was approved in symptomatic patients with bone metastases and no known visceral metastases pre- and post-docetaxel. However, despite significant advances, mCRPC remains a lethal disease. Both primary and acquired resistance have been observed in CRPC patients treated by these new agents. It could be solely cell intrinsic or it is possible that the clonal heterogeneity in treated tumors may result from the adaptive responses to the selective pressures within the tumor microenvironment. The aim of this review is to list current treatment agents of CRPC and summarize recent findings in therapeutic resistance mechanisms.