The changing therapeutic landscape of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) has a poor prognosis and remains a significant therapeutic challenge. Before 2010, only docetaxel-based chemotherapy improved survival in patients with CRPC compared with mitoxantrone. Our improved understanding of the underlying biology of CRPC has heralded a new era in molecular anticancer drug development, with a myriad of novel anticancer drugs for CRPC entering the clinic. These include the novel taxane cabazitaxel, the vaccine sipuleucel-T, the CYP17 inhibitor abiraterone, the novel androgen-receptor antagonist MDV-3100 and the radioisotope alpharadin. With these developments, the management of patients with CRPC is changing. In this Review, we discuss these promising therapies along with other novel agents that are demonstrating early signs of activity in CRPC. We propose a treatment pathway for patients with CRPC and consider strategies to optimize the use of these agents, including the incorporation of predictive and intermediate end point biomarkers, such as circulating tumor cells.     

Tasquinimod: A Novel Angiogenesis Inhibitor–Development in Prostate Cancer

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

Novel therapeutic strategies for metastatic prostate cancer in the post-docetaxel setting

Prostate cancer is the most common noncutaneous cancer and the second leading cause of death from cancer in men in most western countries. Advanced prostate cancer is typically sensitive to androgen‐deprivation therapy, but invariably progresses to the castration‐resistant state. Most current prostate cancer treatments are based on cytotoxicity directed against tumor cells via androgen‐deprivation therapy or chemotherapy. Chemotherapy with docetaxel represents the standard first‐line treatment in patients with castration‐resistant prostate cancer (CRPC). Following progression after treatment with docetaxel, cabazitaxel (XRP6258)–prednisone treatment leads to a significantly longer overall survival (OS) time than with mitoxantrone–prednisone. Several other novel agents are currently being evaluated, including sipuleucel‐T, abiraterone acetate, and MDV3100, as well as the radionuclide alpharadin. The cell‐based immunotherapy sipuleucel‐T produces longer OS times in chemotherapy‐naïve patients, whereas the androgen biosynthesis inhibitor abiraterone acetate results in longer OS times following docetaxel. It is envisioned that these agents will change the standard of care for patients with metastatic CRPC. This review focuses on the clinical development of cabazitaxel and abiraterone acetate.     

Current and emerging treatments in the management of castration-resistant prostate cancer

Historically, patients diagnosed with castration-resistant prostate cancer (CRPC) have had poor survival rates. In recent years there have been significant advances in the treatment of CRPC. In addition to cytotoxic chemotherapy, treating physicians and their patients now have the option of several new agents that target not only androgen- and cytotoxic-mediated pathways, but also the patient's own immune system. In this review, we discuss the existing US FDA-approved therapies, a wide range of experimental treatments that are currently in development, and also palliative options for patients with symptoms secondary to metastatic disease. We also discuss the progression-free survival, overall survival, PSA levels and other end points used in clinical trials in order to evaluate and compare novel therapeutic options for CRPC. Currently, docetaxel and sipuleucel-T are the first line treatment options for patients with CRPC; approved second-line treatments for first line treatment failure are limited to cabazitaxel and abiraterone acetate. Recently, a few experimental agents, MDV3100 and radium-223, have demonstrated efficacy in improving overall survival in patients who had previously failed chemotherapy. These agents, and possibly others introduced in this review, are positioned to change the treatment landscape for CRPC.     

Current and emerging treatments in the management of castration-resistant prostate cancer

Historically, patients diagnosed with castration-resistant prostate cancer (CRPC) have had poor survival rates. In recent years there have been significant advances in the treatment of CRPC. In addition to cytotoxic chemotherapy, treating physicians and their patients now have the option of several new agents that target not only androgen- and cytotoxic-mediated pathways, but also the patient’s own immune system. In this review, we discuss the existing US FDA-approved therapies, a wide range of experimental treatments that are currently in development, and also palliative options for patients with symptoms secondary to metastatic disease. We also discuss the progression-free survival, overall survival, PSA levels and other end points used in clinical trials in order to evaluate and compare novel therapeutic options for CRPC. Currently, docetaxel and sipuleucel-T are the first line treatment options for patients with CRPC; approved second-line treatments for first line treatment failure are limited to cabazitaxel and abiraterone acetate. Recently, a few experimental agents, MDV3100 and radium-223, have demonstrated efficacy in improving overall survival in patients who had previously failed chemotherapy. These agents, and possibly others introduced in this review, are positioned to change the treatment landscape for CRPC.     

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

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

Novel strategies in the treatment of castration-resistant prostate cancer (Review)

Prostate cancer is the most common cancer in men in Europe and the United States, and the third leading cause of death from cancer in Europe. Survival of prostate cancer cells is dependent on the activation of androgen receptors (AR), that are overexpressed in this tumor. Furthermore, ~90% of prostate cancer patients that respond to first-line androgen deprivation therapy (ADT) undergo rapid progression. This condition is defined as castration-resistant prostate cancer (CRPC). Docetaxel-based regimens significantly improve overall survival (OS) in patients with CRPC and represent the only treatment strategy approved by the Food and Drug Administration (FDA). Recently, abiraterone (second hormonal therapy) and cabazitaxel (new taxane) have been shown to improve survival in patients with CRPC who progressed following docetaxel-based chemotherapy. Vaccine therapy has also been demonstrated to improve OS in patients with asymptomatic or minimally symptomatic metastatic CRPC. Additional therapeutic targets have been analyzed in prostate cancer, including apoptosis, angiogenic receptors, vitamin D and Src pathways. Several phase II studies are ongoing. The high frequency of prostate cancer-related metastatic bone disease has led to consider this pathway as a therapeutic target. To this end, several bone-targeted agents have been investigated, most notably zoledronic acid, which is highly effective at stabilizing the bone and preventing skeletal complications. More recently, a nuclear factor-β ligand (RANKL) inhibitor, denosumab, has been developed for the treatment of bone metastases.     

Medical strategies for treatment of castration resistant prostate cancer (CRPC) docetaxel resistant

Current landscape of treatment of castration-resistant prostate cancer (CRPC) has recently changed. Cabazitaxel, a new taxane with potential antineoplastic activity, has been approved by Food and Drug Administration (FDA) after docetaxel failure. In a phase III trial, cabazitaxel showed increased overall survival (OS) compared with mitoxantrone (15.1 vs. 12.7 mo, HR 0.70, 95% CI 0.59-0.83, p < 0.0001). Furthermore, chemotherapy is not the only strategy available: several studies have shown as CRPC remains dependent on androgen receptor function for growth. Abiraterone acetate, an irreversible inhibitor of CYP17, has also been approved by FDA after docetaxel failure. In a phase III trial comparing abiraterone acetate to placebo, abiraterone showed improvement in OS (14.8 vs. 10.4 mo, HR 0.65, 95% CI 0.54-0.77; p < 0.0001). This review will discuss current options and the ongoing trials for second-line treatment of CRPC including chemotherapy, hormonal therapies, antiangiogenetic and immune strategies.     

Castration-resistant prostate cancer: many treatments, many options, many challenges ahead

Although the long natural history of prostate cancer presents challenges in the development of novel therapeutics, major contributions have been observed recently. A better understanding of the long-term complications of androgen deprivation has changed the initial approach to most patients with advanced disease. Specifically, recognition of the limitations of prostate-specific antigen has driven the pursuit of new tools capable of becoming true surrogates for disease outcome. Understanding the molecular biology of castration-resistant prostate cancer (CRPC) has led to a dramatic paradigm shift in the treatment of patients with metastatic disease where the androgen receptor becomes a central therapeutic target. Specific adrenal inhibitors and engineered super androgen receptor inhibitors have become the most promising agents in the disease. Novel immune therapies have been shown to improve survival in selected patients with castration-resistant disease despite the inability to impact traditional markers of response. Similarly, agents such as cabazitaxel and abiraterone acetate have demonstrated clinical benefit are now a standard of care in docetaxel-refractory metastatic CRPC patients. All these changes have occurred in a relatively short period and are likely to change the prostate cancer treatment paradigm. This review summarizes the current management of CRPC and discusses potential future directions.     

New treatment options for patients with metastatic castration-resistant prostate cancer

Chemotherapy for men with metastatic castration-resistant prostate cancer (CRPC) conferred no survival advantage until 2004 when docetaxel was shown to improve survival when compared with mitoxantrone, which was approved for palliation of symptomatic disease in 1996. Since then, clinical trials have concentrated on three main populations of patients with metastatic CRPC: those who are chemotherapy naïve and are asymptomatic or minimally symptomatic, those who need docetaxel therapy, and those who have received docetaxel previously and/or those with symptomatic disease. Over the last year, four Phase III therapeutic trials have met their primary endpoint of improved overall survival: sipuleucel-T in the pre-chemotherapy setting, cabazitaxel and abiraterone in the post-docetaxel setting, and radium-223 for those with symptomatic bone metastases who have received or are not suitable to receive docetaxel. In addition to these therapeutic trials, a Phase III head-to-head trial of denosumab compared to zoledronic acid showed that denosumab was superior to zoledronic acid in delaying or preventing skeletal related events. As a result, the treatment paradigm for metastatic CRPC is changing rapidly. This paper reviews the data from these five completed Phase III trials and places these new agents, as well as those in ongoing Phase III trials, in the context of the old treatment paradigm for metastatic CRPC and discusses some of the challenges ahead for determining optimal timing and sequencing of treatments for metastatic CRPC.     

Efficacy and Safety of Carboplatin Plus Paclitaxel as the First-, Second-, and Third-line Chemotherapy in Men With Castration-resistant Prostate Cancer

IntroductionCarboplatin and paclitaxel (CP) had shown moderate efficacy in treating castration-resistant prostate cancer (CRPC) before standard first-line docetaxel chemotherapy became available. Currently, for patients with homology-directed repair gene defects as well as for unselected patients, platinum chemotherapy is administered after all standard treatments have been ineffective. Here, we retrospectively studied the efficacy and safety of CP administered as the first-, second-, and third-line chemotherapy in patients with CRPC.Patients and MethodsA retrospective chart review was performed for 58 patients with CRPC who received CP between 2001 and 2018 in a single institution. Twenty-seven patients received CP as the first-line chemotherapy, 21 as the second-line after docetaxel, and 10 as the third-line after docetaxel and cabazitaxel. Prostate-specific antigen (PSA) responses (> 50% decline of PSA from baseline), progression-free survival, overall survival, and adverse events were examined.ResultsPSA responses at any time were 55.6%, 19.0%, and 10.0%; PSA responses at 12 weeks were 48.1%, 14.3%, and 10.0%; the median progression-free survival was 3, 1, and 1 month; and the median overall survival was 19, 11, and 6 months, respectively, for the first-, second-, and third-line settings. The only patient who achieved exceptional and durable PSA response in the third-line setting had a deleterious germline BRCA2 mutation (5645C>A). The adverse event profile was favorable.ConclusionCP shows moderate efficacy against CRPC in the first-line setting, but shows little effect in the third-line setting. CP after docetaxel and cabazitaxel may be recommended in selected patients with CRPC with homology-directed repair gene defects.     

Cabazitaxel in patients aged ≥80 years with castration-resistant prostate cancer: Results of a post-marketing surveillance study in Japan

ObjectivesData on the safety and efficacy of cabazitaxel in patients aged ≥80 years with castration-resistant prostate cancer (CRPC) are limited. We report the safety (adverse drug reactions [ADRs]) and efficacy (overall survival [OS], time to treatment failure [TTF], and prostate-specific antigen [PSA] response rates) in patients aged <80 or ≥80 years treated with cabazitaxel for CRPC in clinical practice.Materials and methodsWe performed post-hoc subgroup analyses of a Japanese post-marketing surveillance study involving 662 patients with CRPC treated with cabazitaxel between September 2014 and June 2016.ResultsIn patients aged <80 (n = 610) and ≥80 years (n = 49), median PSA at baseline was 168.7 and 109.0 ng/mL, and 86.7% and 83.7% of patients were previously treated with enzalutamide and/or abiraterone. ADRs (all grade) occurred in 77.2% and 79.6% of patients aged <80 and ≥80 years, with grade three/worse ADRs in 61.8% and 63.3% of patients. Hematologic toxicities were the most common grade three/worse ADRs, including neutropenia, febrile neutropenia, and anemia in both subgroups. No specific ADRs were observed in patients aged ≥80 years. The PSA response and median OS and TTF were 28.3%, 292 days, and 116 days in patients aged ≥80 years, and 29.7%, 319 days, and 125 days in patients aged <80 years.ConclusionCabazitaxel could be a treatment option for CRPC in patients aged ≥80 years based on its safety and efficacy profiles. This is the first report to investigate the safety and efficacy of cabazitaxel in patients aged ≥80 years with CRPC.     

Clinical concepts for cabazitaxel in the management of metastatic castration‐resistant prostate cancer

Prostate cancer is the most common malignancy in male patients. The second‐generation taxanes, cabazitaxel, is a therapeutic option with an overall survival advantage for patients with metastatic castration‐resistant prostate cancer. This review explores specific aspects of cabazitaxel including the duration of treatment, the efficacy of lower dose and effect on the incidence of adverse effects, and optimal sequencing of cabazitaxel. A systematic search of data baselines “PubMed, Ovid Medline, Scopus, and Embase” was carried out using the keywords “cabazitaxel” and “metastatic prostate cancer.” The search was limited to clinical studies performed after October 2010 addressing duration of treatment, the efficacy of lower dose, adverse effects, the sequence of cabazitaxel in relation to other lines of therapy and use in chemotherapy naïve patients. The current evidence supports the utility and safety of cabazitaxel as either a second‐ or third‐line agent after docetaxel, or as an alternative to docetaxel in the chemotherapy‐naive setting. Extended duration of cabazitaxel beyond 10 cycles is feasible and does not appear to lead to cumulative toxicity. In conclusion, cabazitaxel can improve survival in castrate‐resistant prostate cancer with an acceptable risk of toxicity. Studies confirmed the efficacy of reduced dose and utility in patients without prior chemotherapy.     

The safety and efficacy of radium-223 dichloride for the treatment of advanced prostate cancer

Introduction: A number of drugs have been shown to extend life expectancy in castration-resistant prostate cancer (CRPC). Skeletal related events (SREs) secondary to bone metastases cause significant morbidity for men with CRPC. The α-emitting radiopharmaceutical radium-223 dichloride has been shown to improve overall survival, time to symptomatic skeletal events (SSEs) and quality of life in CRPC.

Areas covered: The development of radium-223 from pre-clinical studies to the evidence of efficacy and safety from a phase 3 trial is discussed as well as its pharmacokinetics and metabolism. The integration of radium-223 into routine care for patients with advanced prostate cancer is included including a comparison with other agents in this setting.

Expert commentary: The risk/benefit ratio for radium-223 is very similar to that of other agents used in the CRPC setting and is a treatment option for men unsuitable for cytotoxic chemotherapy because of comorbidities. The ALSYMPCA trial demonstrated an improvement in SSEs with radium-223. This is a clinically relevant end-point as not all radiologically-detected SREs are apparent to patients. The correct sequencing of the life-prolonging treatments available to men with CRPC is subject to debate. Radium-223 therapy should be considered before the development of visceral metastases. Drug-combination studies are underway.     

CCL2 induces resistance to the antiproliferative effect of cabazitaxel in prostate cancer cells

Understanding the mechanism of chemoresistance and disease progression in patients with prostate cancer is important for developing novel treatment strategies. In particular, developing resistance to cabazitaxel is a major challenge in patients with docetaxel‐resistant and castration‐resistant prostate cancer (CRPC) because cabazitaxel is often administered as a last resort. However, the mechanism by which cabazitaxel resistance develops is still unclear. C‐C motif chemokine ligands (CCL) were shown to contribute to the castration resistance of prostate cancer cells via an autocrine mechanism. Therefore, we focused on CCL as key factors of chemoresistance in prostate cancer cells. We previously established a cabazitaxel‐resistant cell line, DU145‐TxR/CxR, from a previously established paclitaxel‐resistant cell line, DU145‐TxR. cDNA microarray analysis revealed that the expression of CCL2 was upregulated in both DU145‐TxR and DU145‐TxR/CxR cells compared with DU145 cells. The secreted CCL2 protein level in DU145‐TxR and DU145‐TxR/CxR cells was also higher than in parental DU145 cells. The stimulation of DU145 cells with CCL2 increased the proliferation rate under treatments with cabazitaxel, and a CCR2 (a specific receptor of CCL2) antagonist suppressed the proliferation of DU145‐TxR and DU145‐TxR/CxR cells under treatments of cabazitaxel. The CCL2‐CCR2 axis decreased apoptosis through the inhibition of caspase‐3 and poly(ADP‐ribose) polymerase (PARP). CCL2 is apparently a key contributor to cabazitaxel resistance in prostate cancer cells. Inhibition of the CCL2‐CCR2 axis may be a potential therapeutic strategy against chemoresistant CRPC in combination with cabazitaxel.     

Sequencing of Cabazitaxel in Metastatic Castrate-Resistant Prostate Cancer: A Case Report

Prostate cancer is a common cancer in men; for metastatic disease, it has a 5-year survival rate of 30%. No FDA-approved therapy for castrate-resistant prostate cancer (CRPC) known to improve survival was available until 2004, when based on a significant survival benefit over mitoxantrone, docetaxel in combination with prednisone was approved. In combination with prednisone, cabazitaxel, which was approved in the United States in 2010, is indicated for patients with metastatic CRPC previously treated with a docetaxel-containing regimen. This case report describes the treatment of a man 58 years of age who was diagnosed with advanced prostate cancer in 2006. He was initially managed with radical prostatectomy followed by androgen deprivation therapy, but a rising prostate-specific antigen (PSA) level led to enrollment in a clinical trial of HE3235 for 6 months. Subsequently, with progression of disease, he was treated with docetaxel for 4 months and then palliative radiation therapy. Cabazitaxel was initiated in October 2010; his condition stabilized within weeks, and he experienced a progressive decline in his PSA level from a peak of 5,424 ng/ml. Continued treatment with cabazitaxel resulted in his being weaned off pain medications and resuming his normal activities. After 16 cycles of cabazitaxel, his PSA declined to 994 ng/ml as of January 2012. He tolerated the cabazitaxel well and occasionally received myeloid growth factors for treatment of neutropenia; otherwise, he experienced only mild diarrhea. This response to cabazitaxel is notable, particularly in light of prior failure of multiple therapies.Key Words: Cabazitaxel, Castrate-resistant prostate cancer (CRPC), Treatment sequencing     

节拍化疗与转移性乳腺癌

节拍化疗是通过抑制肿瘤新生血管生成发挥抗肿瘤作用.研究表明,运用节拍化疗可明显提高转移性乳腺癌患者的生活质量,耐受性好,且有较高的效应/费用比,有望成为转移性乳腺癌的一种全新治疗模式.     

节拍化疗与转移性乳腺癌

节拍化疗是通过抑制肿瘤新生血管生成发挥抗肿瘤作用.研究表明,运用节拍化疗可明显提高转移性乳腺癌患者的生活质量,耐受性好,且有较高的效应/费用比,有望成为转移性乳腺癌的一种全新治疗模式.     

Second-line therapy for castrate-resistant prostate cancer: a literature review

Despite a survival benefit in the first-line treatment of castrate-resistant prostate cancer (CRPC) with docetaxel, the prognosis remains limited. There are increasing options available for patients with CRPC in the second-line setting, but there is currently little consensus regarding the optimal treatment. There have been numerous phase II and retrospective studies examining second-line options in CRPC, including retreatment with docetaxel, mitoxantrone, cyclophosphamide and carboplatin, which can be associated with meaningful responses in a significant minority of patients. In 2010 three randomized trials were published or presented which demonstrated a survival benefit in the second-line setting. These included cabazitaxel compared with mitoxantrone, sipuleucel-T (immunotherapy) and abiraterone acetate versus placebo. Ongoing research in the second-line setting of CRPC to optimize treatment options, with the objectives of survival prolongation, improvement in quality of life and pain management, is still needed.     

节拍化疗与转移性乳腺癌

节拍化疗是通过抑制肿瘤新生血管生成发挥抗肿瘤作用.研究表明,运用节拍化疗可明显提高转移性乳腺癌患者的生活质量,耐受性好,且有较高的效应/费用比,有望成为转移性乳腺癌的一种全新治疗模式.