Metabolic study of methylstenbolone in horses using liquid chromatography-high resolution mass spectrometry and gas chromatography-mass spectrometry.

Methylstenbolone (2,17α-dimethyl-5α-androst-1-en-17ß-ol-3-one) is a synthetic anabolic and androgenic steroid (AAS) sold as an oral 'nutritional supplement' under the brand names 'Ultradrol', 'M-Sten' and 'Methyl-Sten'. Like other AASs, methylstenbolone is a prohibited substance in both human and equine sports. This paper describes the studies of the in vitro and in vivo metabolism of methylstenbolone in horses using LC/HRMS, GC/MS and GC/MS/MS. Phase I in vitro metabolic study of methylstenbolone was performed using homogenised horse liver. Hydroxylation was the only biotransformation observed. Six in vitro metabolites were detected including four mono-hydroxylated metabolites, namely 16α/ß-hydroxymethylstenbolone (M1a, M1b), 20-hydroxymethylstenbolone (M1c), 6-hydroxymethylstenbolone (M1d), and two dihydroxylated methylstenbolone metabolites (M2c-M2d). An in vivo experiment was carried out using two retired thoroughbred geldings. Each horse was administered with 100 mg methylstenbolone supplement by stomach tubing daily for three consecutive days. Methylstenbolone and 14 metabolites were detected in the post-administration urine samples. The proposed in vivo metabolites included 16α/ß-hydroxymethylstenbolone (M1a, M1b), 20-hydroxymethylstenbolone (M1c), two dihydroxylated methylstenbolone (M2a, M2b), 17-epi-methylstenbolone (M3), methasterone (M4), 2,17-dimethylandrostane-16,17-diol-3-one (M5), dihydroxylated and reduced methylstenbolone (M6), 2α,17α-dimethylandrostane-3α,17ß-diol (M7), 2,17-dimethylandrostane-3,16,17-triol (M8a-M8c) and 2,17-dimethylandrostane-2,3,16,17-tetraol (M9), formed from hydroxylation, reduction and epimerisation. Methylstenbolone and ten of its metabolites could be detected in post-administration plasma samples. The highest concentration of methylstenbolone detected in urine was about 10-36 ng/mL at 3-4 h after the last administration, while the maximum concentration in plasma was about 0.4-0.7 ng/mL at 1 h after the last administration. For controlling the misuse of methylstenbolone, M8c and M9 gave the longest detection time in urine, while M4, M5 and M6 were the longest detecting analytes in plasma. They could be detected for up to 5 and 4.5 days respectively in urine and plasma. Apart from 16α/ß-hydroxymethylstenbolone (M1a, M1b), the methylstenbolone metabolites reported herein have never been reported before.

Advances in the management of castration resistant prostate cancer.

Docetaxel based chemotherapy showed survival benefit and emerged as the mainstay of treatment for castration resistant prostate cancer (CRPC) in 2004. However, therapeutic options have expanded rapidly since 2011. The spectrum of new agents is broad and includes drugs that target the androgen axis (enzalutamide, abiraterone), immunotherapy (sipuleucel-T), bone seeking radionuclides (radium-223), and second line chemotherapy (cabazitaxel). In addition, new agents have been developed to reduce skeletal related events (denosumab). Given that docetaxel was the standard first line treatment for metastatic CRPC, the newer oral agents that affect the androgen axis were initially approved in the post-docetaxel setting. However, subsequent randomized trials have led to their approval in the pre-chemotherapy setting as well. Patients with CRPC are clinically heterogeneous, ranging from patients who are asymptomatic and do not have metastases to those with substantial symptoms and both bony and visceral metastases. CRPC is a clinically challenging disease entity, therefore, with a wide array of treatment options and multiple possible sequencing combinations depending on the individual patient. This review will summarize the findings of the randomized trials that led to the approval of the therapies for CRPC. It will also discuss recent guidelines and provide suggestions for sequencing of drugs based on the best available evidence.

Does Gleason score at initial diagnosis predict efficacy of abiraterone acetate therapy in patients with metastatic castration-resistant prostate cancer? An analysis of abiraterone acetate phase III trials.

BACKGROUND: The usefulness of Gleason score (<8 or ≥8) at initial diagnosis as a predictive marker of response to abiraterone acetate (AA) plus prednisone in patients with metastatic castration-resistant prostate cancer (mCRPC) was explored retrospectively. PATIENTS AND METHODS: Initial diagnosis Gleason score was obtained in 1048 of 1195 (COU-AA-301, post-docetaxel) and 996 of 1088 (COU-AA-302, chemotherapy-naïve) patients treated with AA 1 g plus prednisone 5 mg twice daily by mouth or placebo plus prednisone. Efficacy end points included radiographic progression-free survival (rPFS) and overall survival (OS). Distributions and medians were estimated by Kaplan-Meier method and hazard ratio (HR) and 95% confidence interval (CI) by Cox model. RESULTS: Baseline characteristics were similar across studies and treatment groups. Regardless of Gleason score, AA treatment significantly improved rPFS in post-docetaxel [Gleason score <8: median, 6.4 versus 5.5 months (HR = 0.70; 95% CI 0.56-0.86), P = 0.0009 and Gleason score ≥8: median, 5.6 versus 2.9 months (HR = 0.58; 95% CI 0.48-0.72), P < 0.0001] and chemotherapy-naïve patients [Gleason score <8: median, 16.5 versus 8.2 months (HR = 0.50; 95% CI 0.40-0.62), P < 0.0001 and Gleason score ≥8: median, 13.8 versus 8.2 months (HR = 0.61; 95% CI 0.49-0.76), P < 0.0001]. Clinical benefit of AA treatment was also observed for OS, prostate-specific antigen (PSA) response, objective response and time to PSA progression across studies and Gleason score subgroups. CONCLUSION: OS and rPFS trends demonstrate AA treatment benefit in patients with pre- or post-chemotherapy mCRPC regardless of Gleason score at initial diagnosis. The initial diagnostic Gleason score in patients with mCRPC should not be considered in the decision to treat with AA, as tumour metastases may no longer reflect the histology at the time of diagnosis. CLINICAL TRIALS NUMBER: COU-AA-301 (NCT00638690); COU-AA-302 (NCT00887198).

Impact of a pharmacist-led oral chemotherapy-monitoring program in patients with metastatic castrate-resistant prostate cancer.

BACKGROUND: With the introduction of oral chemotherapy, the paradigm for cancer treatment is shifting. Use of oral chemotherapy agents offers a non-invasive option for patients with metastatic castrate-resistant prostate cancer. However, these medications are not without challenges including strict adherence for optimal effects, novel toxicity profiles, frequent lab parameter monitoring, high cost, and proper handling and disposal methods. Pharmacists are positioned to play a key role in providing patients with the education required to assure an optimal treatment course is carried out. METHODS: Two cohorts of patients receiving abiraterone, bicalutamide, or enzalutamide for metastatic castrate-resistant prostate cancer seen in our outpatient cancer center 21 months before and 24 months after the implementation of a pharmacist-led oral chemotherapy-monitoring program in December of 2012 were retrospectively compared. Patients were evaluated for number of interventions, adherence to lab parameter monitoring, and overall time on each therapy. RESULTS: Of the 64 patients identified, 31 patients fulfilled inclusion criteria. A significant increase in the average number of interventions per patient (6.9 vs. 2.6; P = 0.004) and adherence to lab parameter monitoring (10 vs. 3; P = 0.04) in the post-program implementation cohort was found. However, no significant difference in overall time on therapy (10.3 vs. 8.1; P = 0.341) between the two groups was observed. CONCLUSION: These results suggest a potential opportunity exists to maximize oral chemotherapy treatment outcomes with the addition of a formalized monitoring program directed by an oncology pharmacist.

Clinical Relevance of Androgen Receptor Splice Variants in Castration-Resistant Prostate Cancer.

OPINION STATEMENT: Metastatic castration-resistant prostate cancer (mCRPC) currently benefits from a wealth of treatment options, yet still remains lethal in the vast majority of patients. It is becoming increasingly understood that this disease entity continues to evolve over time, acquiring additional and diverse resistance mechanisms with each subsequent therapy used. This dynamic relationship between treatment pressure and disease resistance can be challenging for the managing clinician. The recent discovery of alternate splice variants of the androgen receptor (AR) is one potential mechanism of escape in mCRPC, and recognizing this resistance mechanism might be important for optimal treatment selection for our patients. AR-V7 appears to be the most relevant AR splice variant, and early clinical data suggest that it is a negative prognostic marker in mCRPC. Emerging evidence also suggests that detection of AR-V7 may be associated with resistance to novel hormonal therapy (abiraterone and enzalutamide) but may be compatible with sensitivity to taxane chemotherapy (docetaxel and cabazitaxel). Adding to this complexity is the observation that AR-V7 is a dynamic marker whose status may change across time and depending on selective pressures induced by different therapies. Finally, it is possible that AR-V7 may represent a therapeutic target in mCRPC if drugs can be designed that degrade or inhibit AR splice variants or block their transcriptional activity. Several such agents (including galeterone, EPI-506, and bromodomain/BET inhibitors) are now in clinical development.

Abiraterone acetate for patients with metastatic castration-resistant prostate cancer progressing after chemotherapy: final analysis of a multicentre, open-label, early-access protocol trial.

BACKGROUND: In the final analysis of the phase 3 COU-AA-301 study, abiraterone acetate plus prednisone significantly prolonged overall survival compared with prednisone alone in patients with metastatic castration-resistant prostate cancer progressing after chemotherapy. Here, we present the final analysis of an early-access protocol trial that was initiated after completion of COU-AA-301 to enable worldwide preapproval access to abiraterone acetate in patients with metastatic castration-resistant prostate cancer progressing after chemotherapy. METHODS: We did a multicentre, open-label, early-access protocol trial in 23 countries. We enrolled patients who had metastatic castration-resistant prostate cancer progressing after taxane chemotherapy. Participants received oral doses of abiraterone acetate (1000 mg daily) and prednisone (5 mg twice a day) in 28-day cycles until disease progression, development of sustained side-effects, or abiraterone acetate becoming available in the respective country. The primary outcome was the number of adverse events arising during study treatment and within 30 days of discontinuation. Efficacy measures (time to prostate-specific antigen [PSA] progression and time to clinical progression) were gathered to guide treatment decisions. We included in our analysis all patients who received at least one dose of abiraterone acetate. This study is registered with ClinicalTrials.gov, number NCT01217697. FINDINGS: Between Nov 17, 2010, and Sept 30, 2013, 2314 patients were enrolled into the early-access protocol trial. Median follow-up was 5·7 months (IQR 3·5-10·6). 952 (41%) patients had a grade 3 or 4 treatment-related adverse event, and grade 3 or 4 serious adverse events were recorded in 585 (25%) people. The most common grade 3 and 4 adverse events were hepatotoxicity (188 [8%]), hypertension (99 [4%]), cardiac disorders (52 [2%]), osteoporosis (31 [1%]), hypokalaemia (28 [1%]), and fluid retention or oedema (23 [1%]). 172 (7%) patients discontinued the study because of adverse events (64 [3%] were drug-related), as assessed by the investigator, and 171 (7%) people died. The funder assessed causes of death, which were due to disease progression (85 [4%]), an unrelated adverse experience (72 [3%]), and unknown reasons (14 [1%]). Of the 86 deaths not attributable to disease progression, 18 (<1%) were caused by a drug-related adverse event, as assessed by the investigator. Median time to PSA progression was 8·5 months (95% CI 8·3-9·7) and median time to clinical progression was 12·7 months (11·8-13·8). INTERPRETATION: No new safety signals or unexpected adverse events were found in this early-access protocol trial to assess abiraterone acetate for patients with metastatic castration-resistant prostate cancer who progressed after chemotherapy. Future work is needed to ascertain the most effective regimen of abiraterone acetate to optimise patients' outcomes. FUNDING: Janssen Research & Development.

Somatostatin analogs and disease control in castration-resistant prostate cancer: different biological behavior? Case series and review of the literature.

AIMS AND BACKGROUND: Castration-resistant prostate cancer is a recent biological behavior where disease can elude androgen deprivation therapy (ADT). Several pathways have been described, including neuroendocrine dedifferentiation. Patients with neuroendocrine dedifferentiation show an increase in chromogranin A (CgA) along with a PSA increase. Our aim was to evaluate the response of patients with castration-resistant prostate cancer and high CgA serum levels after treatment with inhibitors of neuroendocrine cells (somatostatin analogs) in combination with ADT. METHODS: From January 2009 to April 2011, 10 patients with castration-resistant prostate cancer and rising PSA levels along with a CgA increase were evaluated. The therapy was based on somatostatin analogs and LHRH anologs. Total PSA and CgA were measured every 2 months. RESULTS: In 9 of the 10 patients, a reduction of the values of pre-treatment CgA was detected, while a reduction of PSA was found in 8 patients. No grade 2 or higher toxicity was recorded. Only 3 patients had grade 1 gastrointestinal toxicity. Time to progression was 13 months. CONCLUSION: Therapy with somatostatin analogs could increase the therapeutic window of ADT with a low toxicity profile in a subpopulation of patients with castration-resistant prostate cancer who experience a rise in CgA due to neuroendocrine regulation.

Abiraterone acetate in metastatic castration-resistant prostate cancer: a retrospective review of the Princess Margaret experience of (I) low dose abiraterone and (II) prior ketoconazole.

INTRODUCTION: Abiraterone (AA) is a CYP17 inhibitor that prolongs survival in men with metastatic castration-resistant prostate cancer (mCRPC). Data suggest similar pharmacokinetics of 250-500 mg of AA with high-fat meals ('low-dose') and 1000 mg in the fasting state ('full-dose'). Ketoconazole (KT) is a less potent CYP17 inhibitor previously widely used in mCRPC. OBJECTIVE: To study outcomes of men with mCRPC treated with low-dose AA and/or with prior exposure to KT. PATIENTS AND METHODS: Retrospective chart review of all men treated with AA at the Princess Margaret Cancer Centre between November 2009 and March 2013. Outcome measures were prostate-specific antigen response rate (PSA-RR), biochemical progression-free survival (bPFS), treatment duration and overall survival (OS). Associations between AA dose or prior KT and outcomes were assessed using chi-square test for PSA-RR and log-rank test for bPFS, treatment duration and OS. RESULTS: In total, 111 men who received AA were evaluable, of which 21 received low-dose AA and 23 received prior KT. There was a non-significant difference in PSA-RR (43% versus 32%, p=0.37), but no significant differences in median bPFS, median treatment duration and median OS (18.7 versus 16.6 months, p=0.25) in the full and low-dose cohorts respectively, and for those who received prior KT or not (PSA-RR 48% versus 38%, p=0.4; median OS 24.2 versus 16.5 months, p=0.066, respectively). CONCLUSIONS: Low-dose AA or prior KT treatment were not associated with poorer outcome in men with mCRPC treated with AA. These observations may have implications for drug sequencing and dose in resource-limited settings.

Prostate cancer: the best fit for enzalutamide in metastatic prostate cancer.

The PREVAIL trial compared enzalutamide and placebo in patients with metastatic castration-resistant prostate cancer who had not received prior chemotherapy, demonstrating an improvement in overall survival and other clinical, radiographic, and biochemical outcomes. Herein, the implications of these data in the rapidly changing landscape of metastatic prostate cancer therapy are discussed.

External validation of a prognostic model predicting overall survival in metastatic castrate-resistant prostate cancer patients treated with abiraterone.

A prognostic model was derived from the population of the COU-AA-301 phase 3 trial for metastatic castrate-resistant prostate cancer patients treated with abiraterone after docetaxel, and it stratifies patients into three risk groups based on clinical parameters. We validated this model in an independent cohort of patients treated with abiraterone after docetaxel outside a clinical trial (group A; n=94) and explored its utility in patients treated with abiraterone in the prechemotherapy setting (group B; n=64). For group A, median overall survival (mOS) was significantly different across the three prognostic groups (good: n=39, mOS: 21.8 mo; intermediate: n=44, mOS: 10.6 mo; poor: n=7, mOS: 6.8 mo; p<0.001; area under the curve [AUC]: 0.71). Analysis of group B confirmed the ability of the model to prognosticate for survival in the prechemotherapy setting: (good: n=44, mOS: 45.6 mo; intermediate or poor: n=20, mOS: 34.5 mo; p=0.042; AUC: 0.61). These results serve to validate the prognostic model in an independent population treated with abiraterone after docetaxel and support clinical implementation of the score. Calibration of the model was poorer in patients receiving abiraterone prechemotherapy. Prospective evaluation of this model in clinical trials is needed.

Abiraterone in heavily pretreated patients with metastatic castrate-resistant prostate cancer.

The aim of this study was to evaluate the activity and tolerability of abiraterone acetate in patients with metastatic castrate-resistant prostate cancer treated previously with more than three lines of chemotherapy. Patients received 1 g of abiraterone acetate (administered as four 250 mg tablets) orally once daily with prednisone at a dose of 5 mg orally twice daily. The primary endpoint was prostate-specific antigen (PSA) response. From August 2011 to January 2013, 36 patients were enrolled. PSA response was observed in 22 patients (61.1%, 95% confidence interval: 0.41-0.81). The median time to PSA progression was 7.3 months and after a median follow-up of 10.1 months, all patients were alive. The treatment was generally well tolerated; side effects secondary to mineralocorticoid excess resulting from blockade of CYP17 were largely controlled with prednisone. Abiraterone acetate seems to be an effective and well-tolerated treatment option for patients with metastatic castrate-resistant prostate cancer irrespective of the number of chemotherapy lines administered previously.

Taxane mechanisms of action: potential implications for treatment sequencing in metastatic castration-resistant prostate cancer.

CONTEXT: In the past few years, there has been a rapid increase in the number of therapies available to treat metastatic castration-resistant prostate cancer (mCRPC). Currently, approved treatments consist of the taxane class of cytotoxic drugs and androgen-targeted therapies. The challenge for clinicians is to decide the best sequence in which to give these therapies to provide the greatest benefit to their patients. OBJECTIVE: To review recent research into the mechanism of action of taxanes in prostate cancer (PCa) cells and the clinical evidence for an interaction between taxanes and androgen-targeted therapies. The implications of these findings for clinical practice are discussed. EVIDENCE ACQUISITION: A nonsystematic review of the relevant medical literature between 2004 and the present, in combination with clinical trial data reported at oncology meetings during 2012, was undertaken. Our perspective, focussing on the potential implications for sequencing of therapies for mCRPC, is provided. EVIDENCE SYNTHESIS: Taxanes are shown to interact with androgen signalling in PCa cells at both the cytoplasmic level (via microtubules) and the nuclear level, affecting transcriptional regulators of androgen-responsive gene expression. Data from clinical trials suggest that androgen deprivation can potentially decrease the efficacy of taxanes in treating PCa. CONCLUSIONS: These findings have important implications for clinical practice, and there is an urgent need for strong clinical data to support a recommendation for an optimal sequence of therapies.

Budgetary impact on a U.S. health plan adopting abiraterone acetate plus prednisone for the treatment of patients with metastatic castration-resistant prostate cancer.

BACKGROUND: Abiraterone acetate, an androgen biosynthesis inhibitor, received FDA approval in 2011 for metastatic castration-resistant prostate cancer (mCRPC) patients who have received prior chemotherapy containing docetaxel. OBJECTIVE: To estimate the projected budgetary impact of adopting abiraterone for mCRPC patients from a U.S. health plan perspective. METHODS: A decision analytic model compared mCRPC treatment cost before and after abiraterone acetate adoption based on a hypothetical 1,000,000-member plan. Plan mCRPC prevalence was derived from prostate cancer incidence reported in U.S. epidemiology statistics and disease progression data from published trials. Market shares for comparator mCRPC treatments (prednisone alone; cabazitaxel + prednisone; mitoxantrone + prednisone; docetaxel retreatment + prednisone) were derived from market research simulation. Abiraterone + prednisone uptake (8% - scenario 1 to 55% - scenario 3) was based on assumptions for illustrative purposes. Treatment costs were computed using prescribing information, treatment duration from phase III trials, and drug costs considering common U.S. cost listing and reimbursement schemes. Prevalence and costs of managing treatment-related toxicities were estimated from literature, treatment guidelines, and expert clinical opinion. The model evaluated the perspectives of a commercial payer with no Medicare beneficiaries and a commercial payer with a subset of Medicare beneficiaries. Sensitivity analyses were conducted to assess changing input values. RESULTS: In each modeled scenario, 57 patients with prior docetaxel therapy received treatment for mCRPC. For the commercial perspective, the incremental per-member-per-month (PMPM) cost attributable to abiraterone ranged from $0.0019 in scenario 1 to $0.0133 in scenario 3. For the commercial/Medicare perspective, the incremental PMPM ranged from $0.0026 in scenario 1 to $0.0176 in scenario 3. The average incremental PMPM cost over 3 scenarios is $0.0112. When testing key sensitivity scenarios, the model indicated that abiraterone treatment duration and cabazitaxel market share were the main drivers of cost. CONCLUSIONS: The model results indicate that reimbursement for abiraterone may have a neutral impact on a U.S. health plan budget given the relatively small size of the eligible prostate cancer population and expected lower toxicity-related costs as compared with chemotherapy. The sensitivity analyses addressing the components of uncertainty in the model show that the budgetary impact of abiraterone is likely low.

Sarcopenia and change in body composition following maximal androgen suppression with abiraterone in men with castration-resistant prostate cancer.

BACKGROUND: Standard medical castration reduces muscle mass. We sought to characterize body composition changes in men undergoing maximal androgen suppression with and without exogenous gluocorticoids. METHODS: Cross-sectional areas of total fat, visceral fat and muscle were measured on serial CT scans in a post-hoc analysis of patients treated in Phase I/II trials with abiraterone followed by abiraterone and dexamethasone 0.5 mg daily. Linear mixed regression models were used to account for variations in time-on-treatment and baseline body mass index (BMI). RESULTS: Fifty-five patients received a median of 7.5 months abiraterone followed by 5.4 months abiraterone and dexamethasone. Muscle loss was observed on single-agent abiraterone (maximal in patients with baseline BMI >30, -4.3%), but no further loss was observed after addition of dexamethasone. Loss of visceral fat was also observed on single-agent abiraterone, (baseline BMI >30 patients -19.6%). In contrast, addition of dexamethasone led to an increase in central visceral and total fat and BMI in all the patients. INTERPRETATION: Maximal androgen suppression was associated with loss of muscle and visceral fat. Addition of low dose dexamethasone resulted in significant increases in visceral and total fat. These changes could have important quality-of-life implications for men treated with abiraterone.

New treatment options for castration-resistant prostate cancer.

PURPOSE: Published efficacy and safety data from clinical trials of three recently approved agents for the management of metastatic castration-resistant prostate cancer (CRPC) are reviewed. SUMMARY: Sipuleucel-T is approved by the Food and Drug Administration (FDA) for the treatment of asymptomatic or minimally symptomatic patients with CRPC. In a placebo-controlled Phase III clinical trial, the use of sipuleucel-T was associated with an average improvement in median overall survival of 4.1 months. Abiraterone acetate and cabazitaxel are approved by FDA as second-line treatments for patients with CRPC who experience disease progression during first-line docetaxel therapy. In Phase III trials, abiraterone acetate was associated with improved overall survival relative to placebo use (14.8 months versus 10.9 months), and cabazitaxel was found to confer an overall survival advantage over mitoxantrone therapy (median survival, 15.1 months versus 12.7 months), corresponding to a 30% reduction in the relative risk of death (hazard ratio, 0.7; 95% confidence interval, 0.59-0.83; p < 0.0001). The three agents range in cost from $40,000 to $93,000 for a full course of therapy. Sipuleucel therapy entails leukapheresis procedures for the collection of autologous cells used in dose preparation, requiring careful planning and coordination of care. CONCLUSION: Sipuleucel-T, abiraterone acetate, and cabazitaxel offer new options for the treatment of patients with CRPC, including those with disease resistant to standard first-line therapies. The agents' varying administration requirements, as well as patient-specific factors and cost issues, are key considerations in the drug selection process.

Antitumour activity of abiraterone acetate against metastatic castration-resistant prostate cancer progressing after docetaxel and enzalutamide (MDV3100).

BACKGROUND: Androgen receptor (AR) signalling remains critically important in metastatic castration-resistant prostate cancer (mCRPC) as confirmed by recent phase III trials, showing a survival advantage for abiraterone acetate and enzalutamide (MDV3100). The antitumour activity of abiraterone and prednisolone in patients pre-treated with enzalutamide is as yet unknown. PATIENTS AND METHODS: We investigated the antitumour activity of abiraterone and prednisolone in patients with mCRPC who had progressed following treatment with docetaxel (Taxotere) and enzalutamide. Clinical data were retrospectively analysed for prostate-specific antigen (PSA) and RECIST responses, clinical benefit and survival. RESULTS: Thirty-eight patients were included in the analysis. The median age was 71 years (range 52-84); metastatic sites included bone disease in 37 patients (97%), lymph nodes in 15 patients (39%) and visceral disease in 10 patients (26%). Abiraterone was well tolerated. Three patients (8%) attained a PSA response, defined as ≥50% decline in PSA confirmed after ≥4 weeks, while seven patients (18%) had a ≥30% PSA decline. The median progression-free survival (PFS) was 2.7 months (95% CI 2.3-4.1). Of the 12 patients assessable radiologically, only 1 (8%) attained a confirmed partial response. CONCLUSION: Abiraterone and prednisolone have modest antitumour activities in patients with mCRPC pretreated with docetaxel and enzalutamide.

Systemic therapy in men with metastatic castration-resistant prostate cancer: a systematic review.

AIMS: Since 2004, docetaxel-based chemotherapy has been the standard of care for men with metastatic castration-resistant prostate cancer (mCRPC), but recently randomised controlled trials (RCTs) of novel agents have shown promise in extending overall survival. These trials have evaluated agents delivered before chemotherapy, to replace or supplement docetaxel, or addressed treatment options for men who have progressed on docetaxel therapy. This review was undertaken to determine which systemic therapies improve cancer- or patient-related outcomes in men with mCRPC. MATERIALS AND METHODS: Searches were carried out in MEDLINE, EMBASE, the Cochrane Library and relevant conference proceedings. Eligible articles included RCTs comparing systemic therapy or combination (excluding primary or secondary androgen deprivation therapy, bone protective agents or radionuclides) with placebo or other agents in men with mCRPC. RESULTS: Twenty-five RCTs met the selection criteria. In chemotherapy-naive patients, targeted therapy with tasquinimod conferred a benefit in progression-free survival. Immunotherapy with sipuleucel-T extended overall survival and was well tolerated, but had no effect on the time to disease progression. Hypercastration with abiraterone extended progression-free survival, whereas overall survival was improved but not statistically proven. In the chemotherapy setting, updated and new trials of docetaxel alone confirmed the survival benefit seen in previous studies. A survival benefit with the addition of estramustine to docetaxel shown in a previous study did not lead to an improvement in pain palliation or quality of life. Trials of combining targeted therapies with docetaxel generally did not extend survival. The addition of bevacizumab improved progression-free survival, but not overall survival. The addition of GVAX immunotherapy or calcitriol was harmful. In the post-chemotherapy setting, progression-free and overall survival benefits were detected with cabazitaxel, abiraterone and enzalutamide. Cabazitaxel was associated with greater toxicity, whereas abiraterone and enzalutamide had less severe adverse effects. Satraplatin and sunitinib both extended progression-free survival, but did not improve overall survival. CONCLUSION: Docetaxel-based chemotherapy remains the standard of care in men with mCRPC who are candidates for palliative systemic therapy. Promising results are emerging with sipuleucel-T and abiraterone in the pre-docetaxel setting and cabazitaxel, abiraterone and enzalutamide in patients who progress on or after docetaxel. Further research to determine the optimal choice, sequence or even the combination of these agents is necessary.

Management of castrate resistant prostate cancer-recent advances and optimal sequence of treatments.

Until 2010, chemotherapy with docetaxel was the only approved agent for treatment of metastatic castrate resistant prostate cancer (mCRPC). Since then, the therapeutic landscape of mCRPC has changed rapidly. Multiple novel agents have received regulatory approval after demonstrating improved overall survival in separate randomized Phase 3 studies. These include immunotherapeutic agent sipuleucel-T, androgen axis inhibitors abiraterone and enzalutamide, and a novel microtubule inhibitor cabazitaxel. More recently, radium-223, a bone-targeting alpha emitting radiopharmaceutical, was reported to improve skeletal related events, as well as overall survival in a Phase 3 randomized study. Additionally, there are several promising agents in the advanced stages of clinical development. Here, we describe the agents recently shown to improve overall survival, and those that have reached the advanced stages of development in Phase 3 clinical trials. We will also propose a strategy for optimal sequencing of these agents in the treatment of mCRPC.