Department of Defense prostate cancer clinical trials consortium: a new instrument for prostate cancer clinical research

The Impact of Circulating Tumor Cell HOXB13 RNA Detection in Men with Metastatic Castration-Resistant Prostate Cancer (mCRPC) Treated with Abiraterone or Enzalutamide

PURPOSE

HOXB13 is an androgen receptor (AR) coregulator specifically expressed in cells of prostatic lineage. We sought to associate circulating tumor cell (CTC) HOXB13 expression with outcomes in men with mCRPC treated with abiraterone or enzalutamide.

EXPERIMENTAL DESIGN

We conducted a retrospective analysis of the multicenter prospective PROPHECY trial of mCRPC men (NCT02269982, n = 118) treated with abiraterone/enzalutamide. CTC detection and HOXB13 complementary DNA (cDNA) expression was measured using a modified Adnatest, grouping patients into 3 categories: CTC 0 (undetectable); CTC+ HOXB13 CTC low (<4 copies); or CTC+ HOXB13 CTC high. The HOXB13 threshold was determined by maximally selected rank statistics for prognostic associations with overall survival (OS) and progression-free survival (PFS).

RESULTS

We included 102 men with sufficient CTC HOXB13 cDNA, identifying 25%, 31%, and 44% of patients who were CTC 0, CTC+ HOXB13 low, and CTC+ HOXB13 high, respectively. Median OS were 25.7, 27.8, and 12.1 months whereas the median PFS were 9.0, 7.7, and 3.8 months, respectively. In subgroup analysis among men with CellSearch CTCs ≥5 copies/mL and adjusting for prior abi/enza treatment and Halabi clinical risk score, the multivariate HR for HOXB13 CTC detection was 2.39 (95% CI, 1.06-5.40) for OS and 2.78 (95% CI, 1.38-5.59) for PFS, respectively. Low HOXB13 CTC detection was associated with lower CTC PSA, PSMA, AR-FL, and AR-V7 detection, and more liver/lung metastases (41% vs. 25%).

CONCLUSIONS

Higher CTC HOXB13 expression is associated with AR-dependent biomarkers in CTCs and is adversely prognostic in the context of potent AR inhibition in men with mCRPC.

Designed, synthesized and biological evaluation of proteolysis targeting chimeras (PROTACs) as AR degraders for prostate cancer treatment

As a continuation of our research on developing potent and potentially safe androgen receptor (AR) degrader, a series of novel proteolysis targeting chimeras (PROTACs) containing the phthalimide degrons with different linker were designed, synthesized and evaluated for their AR degradation activity against LNCaP (AR+) cell line. Most of the synthesized compounds displayed moderate to satisfactory AR binding affinity and might lead to antagonist activity against AR. Among them, compound A16 exhibited the best AR binding affinity (85%) and degradation activity against AR. Due to the strong fluorescence properties of pomalidomide derivatives, B10 was found to be effectively internalized and visualized in LNCaP (AR + ) cells than PC-3 (AR-) cells. Moreover, the molecular docking of A16 with AR and the active site of DDB1-CRBN E3 ubiquitin ligase complex provides guidance to design new PROTAC degrons targeting AR for prostate cancer therapy. These results represent a step toward the development of novel and improved AR PROTACs.

Circulating Tumor Cell Chromosomal Instability and Neuroendocrine Phenotype by Immunomorphology and Poor Outcomes in Men with mCRPC Treated with Abiraterone or Enzalutamide

PURPOSE

While the detection of AR-V7 in circulating tumor cells (CTC) is associated with resistance to abiraterone or enzalutamide in men with metastatic castration-resistant prostate cancer (mCRPC), it only accounts for a minority of this resistance. Neuroendocrine (NE) differentiation or chromosomal instability (CIN) may be additional mechanisms that mediate resistance.

EXPERIMENTAL DESIGN

PROPHECY was a multicenter prospective study of men with high-risk mCRPC starting abiraterone or enzalutamide. A secondary objective was to assess Epic CTC CIN and NE phenotypes before abiraterone or enzalutamide and at progression. The proportional hazards (PH) model was used to investigate the prognostic importance of CIN and NE in predicting progression-free survival and overall survival (OS) adjusting for CTC number (CellSearch), AR-V7, prior therapy, and clinical risk score. The PH model was utilized to validate this association of NE with OS in an external dataset of patients treated similarly at Memorial Sloan Kettering Cancer Center (MSKCC; New York, NY).

RESULTS

We enrolled 118 men with mCRPC starting on abiraterone or enzalutamide; 107 were evaluable on the Epic platform. Of these, 36.4% and 8.4% were CIN positive and NE positive, respectively. CIN and NE were independently associated with worse OS [HR, 2.2; 95% confidence interval (CI), 1.2-4.0 and HR 3.8; 95% CI, 1.2-12.3, respectively] when treated with abiraterone/enzalutamide. The prognostic significance of NE positivity for worse OS was confirmed in the MSKCC dataset (n = 173; HR, 5.7; 95% CI, 2.6-12.7).

CONCLUSIONS

A high CIN and NE CTC phenotype is independently associated with worse survival in men with mCRPC treated with abiraterone/enzalutamide, warranting further prospective controlled predictive studies to inform treatment decisions.

Prospective Multicenter Study of Circulating Tumor Cell AR-V7 and Taxane Versus Hormonal Treatment Outcomes in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Androgen receptor splice variant 7 (AR-V7) detection in circulating tumor cells (CTCs) is associated with a low probability of response and short progression-free (PFS) and overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide or abiraterone. However, it is unclear whether such men benefit from taxane chemotherapy.

PATIENTS AND METHODS

PROPHECY is a multicenter prospective blinded study of patients with poor-risk mCRPC starting abiraterone or enzalutamide and observed through subsequent progression and taxane chemotherapy. We assessed AR-V7 status using the Johns Hopkins modified AdnaTest CTC AR-V7 messenger RNA assay and the Epic Sciences CTC nuclear-localized AR-V7 protein assay before treatment. The primary objective was to validate the independent prognostic value of CTC AR-V7 status based on radiographic/clinical PFS. OS, confirmed prostate-specific antigen (PSA), and objective radiologic responses were secondary end points.

RESULTS

We enrolled 118 men with mCRPC treated with abiraterone or enzalutamide, 51 of whom received subsequent docetaxel or cabazitaxel. Pretreatment CTC AR-V7 status by the Johns Hopkins and Epic Sciences assays was independently associated with worse PFS (hazard ratio [HR], 1.7; 95% CI, 1.0 to 2.9 and HR, 2.1; 95% CI, 1.0 to 4.4, respectively) and OS (HR, 3.3; 95% CI, 1.7 to 6.3 and HR, 3.0; 95% CI, 1.4 to 6.3, respectively) and a low probability of confirmed PSA responses, ranging from 0% to 11%, during treatment with abiraterone or enzalutamide. At progression, subsequent CTC AR-V7 detection was not associated with an inferior PSA or radiographic response or worse PFS or OS with subsequent taxane chemotherapy after adjusting for CellSearch CTC enumeration and clinical prognostic factors.

CONCLUSION

Detection of AR-V7 in CTCs by two different blood-based assays is independently associated with shorter PFS and OS with abiraterone or enzalutamide, but such men with AR-V7-positive disease still experience clinical benefits from taxane chemotherapy.

Prospective Multicenter Validation of Androgen Receptor Splice Variant 7 and Hormone Therapy Resistance in High-Risk Castration-Resistant Prostate Cancer: The PROPHECY Study

PURPOSE

Androgen receptor splice variant 7 (AR-V7) results in a truncated receptor, which leads to ligand-independent constitutive activation that is not inhibited by anti-androgen therapies, including abiraterone or enzalutamide. Given that previous reports suggested that circulating tumor cell (CTC) AR-V7 detection is a poor prognostic indicator for the clinical efficacy of secondary hormone therapies, we conducted a prospective multicenter validation study.

PATIENTS AND METHODS

PROPHECY (ClinicalTrials.gov identifier: NCT02269982) is a multicenter, prospective-blinded study of men with high-risk mCRPC starting abiraterone acetate or enzalutamide treatment. The primary objective was to validate the prognostic significance of baseline CTC AR-V7 on the basis of radiographic or clinical progression free-survival (PFS) by using the Johns Hopkins University modified-AdnaTest CTC AR-V7 mRNA assay and the Epic Sciences CTC nuclear-specific AR-V7 protein assay. Overall survival (OS) and prostate-specific antigen responses were secondary end points.

RESULTS

We enrolled 118 men with mCRPC who were starting abiraterone or enzalutamide treatment. AR-V7 detection by both the Johns Hopkins and Epic AR-V7 assays was independently associated with shorter PFS (hazard ratio, 1.9 [95% CI, 1.1 to 3.3; P = .032] and 2.4 [95% CI, 1.1 to 5.1; P = .020], respectively) and OS (hazard ratio, 4.2 [95% CI, 2.1 to 8.5] and 3.5 [95% CI, 1.6 to 8.1], respectively) after adjusting for CTC number and clinical prognostic factors. Men with AR-V7–positive mCRPC had fewer confirmed prostate-specific antigen responses (0% to 11%) or soft tissue responses (0% to 6%). The observed percentage agreement between the two AR-V7 assays was 82%.

CONCLUSION

Detection of AR-V7 in CTCs by two blood-based assays is independently associated with shorter PFS and OS with abiraterone or enzalutamide, and such men with mCRPC should be offered alternative treatments.

Prostate Cancer Disparity, Chemoprevention, and Treatment by Specific Medicinal Plants

Prostate cancer (PC) is one of the most common cancers in men. The global burden of this disease is rising. Its incidence and mortality rates are higher in African American (AA) men compared to white men and other ethnic groups. The treatment decisions for PC are based exclusively on histological architecture, prostate-specific antigen (PSA) levels, and local disease state. Despite advances in screening for and early detection of PC, a large percentage of men continue to be diagnosed with metastatic disease including about 20% of men affected with a high mortality rate within the African American population. As such, this population group may benefit from edible natural products that are safe with a low cost. Hence, the central goal of this article is to highlight PC disparity associated with nutritional factors and highlight chemo-preventive agents from medicinal plants that are more likely to reduce PC. To reach this central goal, we searched the PubMed Central database and the Google Scholar website for relevant papers. Our search results revealed that there are significant improvements in PC statistics among white men and other ethnic groups. However, its mortality rate remains significantly high among AA men. In addition, there are limited studies that have addressed the benefits of medicinal plants as chemo-preventive agents for PC treatment, especially among AA men. This review paper addresses this knowledge gap by discussing PC disparity associated with nutritional factors and highlighting the biomedical significance of three medicinal plants (curcumin, garlic, and Vernonia amygdalina) that show a great potential to prevent/treat PC, as well as to reduce its incidence/prevalence and mortality, improve survival rate, and reduce PC-related health disparity.

Mechanisms and funding opportunities in genitourinary cancer clinical research

Progress in the prevention, diagnosis, and treatment of genitourinary cancers is dependent on well-conducted clinical trials. The complexity and cost of clinical research continues to escalate, and success is dependent on adequate funding. Opportunities to fund such research include federal, industry, and private sources. The mechanisms whereby larger trials are conducted include contract research organizations, publically- and privately funded consortia, and the National Clinical Trials Network of the National Cancer Institute. The National Clinical Trials Network is the prime venue for investigators to conduct independent, phase III trials in the United States.

Pharmacokinetic/pharmacodynamic drug evaluation of enzalutamide for treating prostate cancer

INTRODUCTION

Enzalutamide is the first approved second-generation androgen receptor (AR) antagonist in the treatment of metastatic castration-resistant prostate cancer (mCRPC) with or without docetaxel-based chemotherapy. Over the past 5 years, a number of attempts were made to determine the efficacy of enzalutamide in the different clinical settings. Areas covered: A literature search was performed at the PubMed, Embase, and Web of Science database to collect the most relevant and impactful studies, including basic science investigations, clinical trials, and reviews. This article focuses on the pharmacology, efficacy, tolerability, and future perspective of enzalutamide. Expert opinion: The treatment paradigm of CRPC has been dramatically challenged of late. Enzalutamide are in wide use because of its favorable efficacy and safety, but primary or acquired resistance to the drug will eventually develop. Further studies are thus necessary to identify appropriate patients who can achieve apparent benefits from enzalutamide alone or in combination with other drugs.

Intermittent Chemotherapy as a Platform for Testing Novel Agents in Patients With Metastatic Castration-Resistant Prostate Cancer: A Department of Defense Prostate Cancer Clinical Trials Consortium Randomized Phase II Trial of Intermittent Docetaxel With Prednisone With or Without Maintenance GM-CSF

BACKGROUND

Immunotherapy with granulocyte-macrophage colony-stimulating factor (GM-CSF), an agent that previously demonstrated antitumor activity, was evaluated within an intermittent chemotherapy framework of docetaxel with prednisone (D+P) in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

mCRPC patients with ≥ 50% prostate-specific antigen (PSA) decline after 6 cycles of D+P were randomized to either GM-CSF or observation (Obs). At disease progression (PD), D+P was reinitiated for 6 cycles followed by the same "off chemotherapy" regimen in patients eligible for chemotherapy interruption. The sequence was repeated until PD during chemotherapy, lack of PSA response to chemotherapy, or unacceptable toxicity. The primary end point was time to chemotherapy resistance (TTCR).

RESULTS

Of 125 patients enrolled, 52 (42%) experienced ≥ 50% PSA decline on induction D+P and were randomized to GM-CSF (n = 27) or Obs (n = 25). The median time to PD was 3.3 months (95% confidence interval [CI], 2.4-3.5) and 1.5 months (95% CI, 1.5-2.4) during the initial course of GM-CSF and Obs, respectively. Twelve of 26 (46%) patients responded to a second course of D+P. Eleven randomized patients (21%) experienced PD during chemotherapy, precluding accurate assessment of TTCR. The remaining 41 randomized patients discontinued study for lack of PSA response to chemotherapy (n = 8), patient choice to not restart chemotherapy with PSA PD (n = 13), toxicity (n = 7), or study withdrawal (n = 13).

CONCLUSION

Conducting a prospective study in mCRPC with maintenance immunotherapy within the framework of intermittent chemotherapy was feasible. The use of PSA instead of radiographic end points limited the number of evaluable patients. This study provides important insight into designing contemporary intermittent chemotherapy trials with maintenance immunotherapy in patients with advanced prostate cancer.

Critical analysis of contemporary clinical research in muscle-invasive and metastatic urothelial cancer: a report from the Bladder Cancer Advocacy Network Clinical Trials Working Group

BACKGROUND

There have been no improvements in the treatment of metastatic urothelial cancer in the past several decades. A census of contemporary clinical research in this disease was performed to identify potential barriers and opportunities.

METHODS

These authors performed a search for clinical trials exploring interventions in muscle-invasive and metastatic urothelial cancer, using the ClinicalTrials.gov registry. Data extracted from the registry included title, recruitment status, interventions, sponsor, phase, enrollment, study design, and study sites.

RESULTS

Among 120 eligible trials exploring interventions in muscle-invasive and metastatic urothelial cancer, 73% were phase 2 and 73% were nonrandomized. The majority (63%) involved treatment in the metastatic disease state. The median planned enrollment size per trial was 45 patients (interquartile range, 47 patients). The majority of trials (55%) involved ≤ 3 study sites. Trials most commonly explored interventions in the first-line metastatic (30%) or second-line metastatic (37%) settings. Targeted therapeutics were studied in 58% of the trials. Among 56 trials that completed enrollment, the median time to complete accrual was 50 months (range, 10-109 months), and these trials enrolled a median of 40 patients per trial (interquartile range, 44 patients).

CONCLUSIONS

The majority of contemporary clinical trials in muscle-invasive and metastatic urothelial cancer are small, nonrandomized, phase 2 trials involving 1 to 3 study sites. Enhanced communication and collaboration among the urothelial cancer community, and other stakeholders, is needed to facilitate the design and conduct of trials capable of expediting progress in this disease.

Repurposing itraconazole as a treatment for advanced prostate cancer: a noncomparative randomized phase II trial in men with metastatic castration-resistant prostate cancer

BACKGROUND

The antifungal drug itraconazole inhibits angiogenesis and Hedgehog signaling and delays tumor growth in murine prostate cancer xenograft models. We conducted a noncomparative, randomized, phase II study evaluating the antitumor efficacy of two doses of oral itraconazole in men with metastatic prostate cancer.

PATIENTS AND METHODS

We randomly assigned 46 men with chemotherapy-naïve metastatic castration-resistant prostate cancer (CRPC) to receive low-dose (200 mg/day) or high-dose (600 mg/day) itraconazole until disease progression or unacceptable toxicity. The primary endpoint was the prostate-specific antigen (PSA) progression-free survival (PPFS) rate at 24 weeks; a 45% success rate in either arm was prespecified as constituting clinical significance. Secondary endpoints included the progression-free survival (PFS) rate and PSA response rate (Prostate Cancer Working Group criteria). Exploratory outcomes included circulating tumor cell (CTC) enumeration, serum androgen measurements, as well as pharmacokinetic and pharmacodynamic analyses.

RESULTS

The high-dose arm enrolled to completion (n = 29), but the low-dose arm closed early (n = 17) because of a prespecified futility rule. The PPFS rates at 24 weeks were 11.8% in the low-dose arm and 48.0% in the high-dose arm. The median PFS times were 11.9 weeks and 35.9 weeks, respectively. PSA response rates were 0% and 14.3%, respectively. In addition, itraconazole had favorable effects on CTC counts, and it suppressed Hedgehog signaling in skin biopsy samples. Itraconazole did not reduce serum testosterone or dehydroepiandrostenedione sulfate levels. Common toxicities included fatigue, nausea, anorexia, rash, and a syndrome of hypokalemia, hypertension, and edema.

CONCLUSION

High-dose itraconazole (600 mg/day) has modest antitumor activity in men with metastatic CRPC that is not mediated by testosterone suppression.

A phase 2 study of KX2-391, an oral inhibitor of Src kinase and tubulin polymerization, in men with bone-metastatic castration-resistant prostate cancer

PURPOSE

KX2-391 is an oral non-ATP-competitive inhibitor of Src kinase and tubulin polymerization. In phase 1 trials, prostate-specific antigen (PSA) declines were seen in patients with advanced prostate cancer. We conducted a single-arm phase 2 study evaluating KX2-391 in men with chemotherapy-naïve bone-metastatic castration-resistant prostate cancer (CRPC).

METHODS

We treated 31 patients with oral KX2-391 (40 mg twice-daily) until disease progression or unacceptable toxicity. The primary endpoint was 24-week progression-free survival (PFS); a 50 % success rate was pre-defined as clinically significant. Secondary endpoints included PSA progression-free survival (PPFS) and PSA response rates. Exploratory outcomes included pharmacokinetic studies, circulating tumor cell (CTC) enumeration, and analysis of markers of bone resorption [urinary N-telopeptide (uNTx); C-telopeptide (CTx)] and formation [bone alkaline phosphatase (BAP); osteocalcin].

RESULTS

The trial closed early after accrual of 31 patients, due to a pre-specified futility rule. PFS at 24 weeks was 8 %, and median PFS was 18.6 weeks. The PSA response rate (≥ 30 % decline) was 10 %, and median PPFS was 5.0 weeks. Additionally, 18 % of men with unfavorable (≥ 5) CTCs at baseline converted to favorable (<5) CTCs with treatment. The proportion of men with declines in bone turnover markers was 32 % for uNTx, 21 % for CTx, 10 % for BAP, and 25 % for osteocalcin. In pharmacokinetic studies, median C max was 61 (range 16-129) ng/mL, and median AUC was 156 (35-348) ng h/mL. Common toxicities included hepatic derangements, myelosuppression, fatigue, nausea, and constipation.

CONCLUSION

KX2-391 dosed at 40 mg twice-daily lacks antitumor activity in men with CRPC, but has modest effects on bone turnover markers. Because a C max of ≥142 ng/mL is required for tubulin polymerization inhibition (defined from preclinical studies), higher once-daily dosing will be used in future trials.

Increased survival with enzalutamide in prostate cancer after chemotherapy

BACKGROUND

Enzalutamide (formerly called MDV3100) targets multiple steps in the androgen-receptor-signaling pathway, the major driver of prostate-cancer growth. We aimed to evaluate whether enzalutamide prolongs survival in men with castration-resistant prostate cancer after chemotherapy.

METHODS

In our phase 3, double-blind, placebo-controlled trial, we stratified 1199 men with castration-resistant prostate cancer after chemotherapy according to the Eastern Cooperative Oncology Group performance-status score and pain intensity. We randomly assigned them, in a 2:1 ratio, to receive oral enzalutamide at a dose of 160 mg per day (800 patients) or placebo (399 patients). The primary end point was overall survival.

RESULTS

The study was stopped after a planned interim analysis at the time of 520 deaths. The median overall survival was 18.4 months (95% confidence interval [CI], 17.3 to not yet reached) in the enzalutamide group versus 13.6 months (95% CI, 11.3 to 15.8) in the placebo group (hazard ratio for death in the enzalutamide group, 0.63; 95% CI, 0.53 to 0.75; P<0.001). The superiority of enzalutamide over placebo was shown with respect to all secondary end points: the proportion of patients with a reduction in the prostate-specific antigen (PSA) level by 50% or more (54% vs. 2%, P<0.001), the soft-tissue response rate (29% vs. 4%, P<0.001), the quality-of-life response rate (43% vs. 18%, P<0.001), the time to PSA progression (8.3 vs. 3.0 months; hazard ratio, 0.25; P<0.001), radiographic progression-free survival (8.3 vs. 2.9 months; hazard ratio, 0.40; P<0.001), and the time to the first skeletal-related event (16.7 vs. 13.3 months; hazard ratio, 0.69; P<0.001). Rates of fatigue, diarrhea, and hot flashes were higher in the enzalutamide group. Seizures were reported in five patients (0.6%) receiving enzalutamide.

CONCLUSIONS

Enzalutamide significantly prolonged the survival of men with metastatic castration-resistant prostate cancer after chemotherapy. (Funded by Medivation and Astellas Pharma Global Development; AFFIRM ClinicalTrials.gov number, NCT00974311.).

Building the informatics infrastructure for comparative effectiveness research (CER): a review of the literature

BACKGROUND

Technological advances in clinical informatics have made large amounts of data accessible and potentially useful for research. As a result, a burgeoning literature addresses efforts to bridge the fields of health services research and biomedical informatics. The Electronic Data Methods Forum review examines peer-reviewed literature at the intersection of comparative effectiveness research and clinical informatics. The authors are specifically interested in characterizing this literature and identifying cross-cutting themes and gaps in the literature.

METHODS

A 3-step systematic literature search was conducted, including a structured search of PubMed, manual reviews of articles from selected publication lists, and manual reviews of research activities based on prospective electronic clinical data. Two thousand four hundred thirty-five citations were identified as potentially relevant. Ultimately, a full-text review was performed for 147 peer-reviewed papers.

RESULTS

One hundred thirty-two articles were selected for inclusion in the review. Of these, 88 articles are the focus of the discussion in this paper. Three types of articles were identified, including papers that: (1) provide historical context or frameworks for using clinical informatics for research, (2) describe platforms and projects, and (3) discuss issues, challenges, and applications of natural language processing. In addition, 2 cross-cutting themes emerged: the challenges of conducting research in the absence of standardized ontologies and data collection; and unique data governance concerns related to the transfer, storage, deidentification, and access to electronic clinical data. Finally, the authors identified several current gaps on important topics such as the use of clinical informatics for cohort identification, cloud computing, and single point access to research data.

Phase 2 study of neoadjuvant docetaxel plus bevacizumab in patients with high-risk localized prostate cancer: a Prostate Cancer Clinical Trials Consortium trial

BACKGROUND

Treatment of high-risk localized prostate cancer remains inadequate. The authors performed a phase 2 multicenter trial of neoadjuvant docetaxel plus bevacizumab before radical prostatectomy.

METHODS

Eligibility included any of the following: prostate-specific antigen (PSA) >20 ng/mL or PSA velocity >2 ng/mL/y, cT3 disease, any biopsy Gleason score 8 to 10, and Gleason score 7 with T3 disease by endorectal magnetic resonance imaging (MRI) at 1.5 T. Also, those with ≥50% biopsy cores involved and either Gleason score 7, PSA >10, or cT2 disease were eligible. Patients were treated with docetaxel 70 mg/m(2) every 3 weeks for 6 cycles and bevacizumab 15 mg/m(2) every 3 weeks for 5 cycles. The primary endpoint was partial response by endorectal MRI.

RESULTS

Forty-one patients were treated. Median age was 55 years (range, 40-66 years). Baseline characteristics included: median PSA, 10.1 ng/mL; cT2, 49%, cT3, 32%; and Gleason score 8 to 10, 73%. Thirty-eight of 41 (93%) patients completed all 6 cycles. Grade ≥3 adverse events were rare, although 3 of 41 (7%) experienced febrile neutropenia. Twelve patients (29%; 95% confidence interval [CI], 16%-45%) achieved a >50% reduction in tumor volume, and 9 patients (22%; 95% CI, 11%-38%) achieved a >50% post-treatment decline in PSA. Thirty-seven of the 41 patients underwent radical prostatectomy; there were no complete pathologic responses.

CONCLUSIONS

Neoadjuvant docetaxel and bevacizumab is safe, and results in reductions in both tumor volume and serum PSA, in men with high-risk localized prostate cancer. The role of neoadjuvant chemotherapy in prostate cancer, and perioperative antiangiogenic therapy in general, requires further elucidation through ongoing and planned trials.

Developing imaging strategies for castration resistant prostate cancer

Recent advances in the understanding of castrate-resistant prostate cancer (CRPC) have lead to a growing number of experimental therapies, many of which are directed against the androgen-receptor (AR) signaling axis. These advances generate the need for reliable molecular imaging biomarkers to non-invasively determine efficacy, and to better guide treatment selection of these promising AR-targeted drugs. Methods. We draw on our own experience, supplemented by review of the current literature, to discuss the systematic development of imaging biomarkers for use in the context of CRPC, with a focus on bone scintigraphy, F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) and PET imaging of the AR signaling axis. Results. The roadmap to biomarker development mandates rigorous standardization and analytic validation of an assay before it can be qualified successfully for use in an appropriate clinical context. The Prostate Cancer Working Group 2 (PCWG2) criteria for "radiographic" progression by bone scintigraphy serve as a paradigm of this process. Implemented by the Prostate Cancer Clinical Trials Consortium (PCCTC), these consensus criteria may ultimately enable the co-development of more potent and versatile molecular imaging biomarkers. Purported to be superior to single-photon bone scanning, the added value of Na(18)F-PET for imaging of bone metastases is still uncertain. FDG-PET already plays an integral role in the management of many diseases, but requires further evaluation before being qualified in the context of CRPC. PET tracers that probe the AR signaling axis, such as (18)F-FDHT and (89)Zr-591, are now under development as pharmacodynamic markers, and as markers of efficacy, in tandem with FDG-PET. Semi-automated analysis programs for facilitating PET interpretation may serve as a valuable tool to help navigate the biomarker roadmap. Conclusions. Molecular imaging strategies, particularly those that probe the AR signaling axis, have the potential to accelerate drug development in CRPC. The development and use of analytically valid imaging biomarkers will increase the likelihood of clinical qualification, and ultimately lead to improved patient outcomes.

Antitumour activity of MDV3100 in castration-resistant prostate cancer: a phase 1-2 study

BACKGROUND

MDV3100 is an androgen-receptor antagonist that blocks androgens from binding to the androgen receptor and prevents nuclear translocation and co-activator recruitment of the ligand-receptor complex. It also induces tumour cell apoptosis, and has no agonist activity. Because growth of castration-resistant prostate cancer is dependent on continued androgen-receptor signalling, we assessed the antitumour activity and safety of MDV3100 in men with this disease.

METHODS

This phase 1-2 study was undertaken in five US centres in 140 patients. Patients with progressive, metastatic, castration-resistant prostate cancer were enrolled in dose-escalation cohorts of three to six patients and given an oral daily starting dose of MDV3100 30 mg. The final daily doses studied were 30 mg (n=3), 60 mg (27), 150 mg (28), 240 mg (29), 360 mg (28), 480 mg (22), and 600 mg (3). The primary objective was to identify the safety and tolerability profile of MDV3100 and to establish the maximum tolerated dose. The trial is registered with ClinicalTrials.gov, number NCT00510718.

FINDINGS

We noted antitumour effects at all doses, including decreases in serum prostate-specific antigen of 50% or more in 78 (56%) patients, responses in soft tissue in 13 (22%) of 59 patients, stabilised bone disease in 61 (56%) of 109 patients, and conversion from unfavourable to favourable circulating tumour cell counts in 25 (49%) of the 51 patients. PET imaging of 22 patients to assess androgen-receptor blockade showed decreased (18)F-fluoro-5alpha-dihydrotestosterone binding at doses from 60 mg to 480 mg per day (range 20-100%). The median time to progression was 47 weeks (95% CI 34-not reached) for radiological progression. The maximum tolerated dose for sustained treatment (>28 days) was 240 mg. The most common grade 3-4 adverse event was dose-dependent fatigue (16 [11%] patients), which generally resolved after dose reduction.

INTERPRETATION

We recorded encouraging antitumour activity with MDV3100 in patients with castration-resistant prostate cancer. The results of this phase 1-2 trial validate in man preclinical studies implicating sustained androgen-receptor signalling as a driver in this disease.

FUNDING

Medivation, the Prostate Cancer Foundation, National Cancer Institute, the Howard Hughes Medical Institute, Doris Duke Charitable Foundation, and Department of Defense Prostate Cancer Clinical Trials Consortium.