ARN-509 is a novel androgen receptor (AR) antagonist for the treatment of castration-resistant prostate cancer (CRPC). ARN-509 inhibits AR nuclear translocation and AR binding to androgen response elements and, unlike bicalutamide, does not exhibit agonist properties in the context of AR overexpression. This first-in-human phase I study assessed safety, tolerability, pharmacokinetics, pharmacodynamics, and antitumor activity of ARN-509 in men with metastatic CRPC.
Patients and Methods
Thirty patients with progressive CRPC received continuous daily oral ARN-509 at doses between 30 and 480 mg, preceded by administration of a single dose followed by a 1-week observation period with pharmacokinetic sampling. Positron emission tomography/computed tomography imaging was conducted to monitor [18F]fluoro-α-dihydrotestosterone (FDHT) binding to AR in tumors before and during treatment. Primary objective was to determine pharmacokinetics, safety, and recommended phase II dose.
Pharmacokinetics were linear and dose proportional. Prostate-specific antigen declines at 12 weeks (≥ 50% reduction from baseline) were observed in 46.7% of patients. Reduction in FDHT uptake was observed at all doses, with a plateau in response at ≥ 120-mg dose, consistent with saturation of AR binding. The most frequently reported adverse event was grade 1/2 fatigue (47%). One dose-limiting toxicity event (grade 3 abdominal pain) occurred at the 300-mg dose. Dose escalation to 480 mg did not identify a maximum-tolerated dose.
ARN-509 was safe and well tolerated, displayed dose-proportional pharmacokinetics, and demonstrated pharmacodynamic and antitumor activity across all dose levels tested. A maximum efficacious dose of 240 mg daily was selected for phase II exploration based on integration of preclinical and clinical data.
High-risk disease accounts for approximately 15% of prostate cancer diagnoses, but the current definitions include a heterogeneous group of patients with a range of prognoses. High-risk prostate cancers have the potential to progress to a lethal phenotype that can be fatal, in marked contrast to low-risk tumours deemed suitable for active surveillance,. The optimal management of this patient sub-group is evolving. A refined classification scheme is needed to enable the early and accurate identification of high-risk disease so that more effective treatment paradigms can be developed. Several principles have been established from clinical trials and are discussed in this review, while other questions remain unanswered. This review critically evaluates the existing literature focused on defining the high-risk population, the management therein, and future directions to optimize care.
There is currently no imaging biomarker for metastatic prostate cancer. The bone scan index (BSI) is a promising candidate, being a reproducible, quantitative expression of tumor burden seen on bone scintigraphy. Prior studies have shown the prognostic value of a baseline BSI. This study tested whether treatment-related changes in BSI are prognostic for survival and compared BSI to prostate-specific antigen (PSA) as an outcome measure.
Patients and Methods
We retrospectively examined serial bone scans from patients with castration-resistant metastatic prostate cancer (CRMPC) enrolled in four clinical trials. We calculated BSI at baseline and at 3 and 6 months on treatment and performed univariate and bivariate analyses of PSA, BSI, and survival.
Eighty-eight patients were scanned, 81 of whom have died. In the univariate analysis, the log percent change in BSI from baseline to 3 and 6 months on treatment prognosticated for survival (hazard ratio [HR], 2.44; P = .0089 and HR, 2.54; P < .001, respectively). A doubling in BSI resulted in a 1.9-fold increase in risk of death. Log percent change in PSA at 6 months on treatment was also associated with survival (HR, 1.298; P = .013). In the bivariate analysis, change in BSI while adjusting for PSA was prognostic at 3 and 6 months on treatment (HR, 2.368; P = .012 and HR, 2.226; P = .002, respectively), but while adjusting for BSI, PSA was not prognostic.
These data furnish early evidence that on-treatment changes in BSI are a response indicator and support further exploration of bone scintigraphy as an imaging biomarker in CRMPC.
Biomarkers based on detecting prostate cancer-specific transcripts are associated with inferior outcomes, but their validation in a clinical context is lacking.
To determine whether detecting prostate cancer enhanced transcripts in whole blood using an analytically valid assay has prognostic significance relative to circulating tumor cell (CTC) enumeration.
Design, Setting, and Participants
The predictive value for overall survival of the detection in whole blood by reverse transcription real-time polymerase chain reaction (RT-PCR) of KLK3, KLK2, HOXB13, GRHL2, and FOXA1 was studied in 97 men with metastatic castration-resistant prostate cancer (mCRPC).
2.5ml of blood was collected in PAXgene tubes for total RNA extraction and 7.5 ml for CTC enumeration from patients with progressive mCRPC.
Outcome Measurements and Statistical Analysis
Prostate cancer enriched genes were detected using a sensitive RT-PCR assay in whole blood from patients with mCRPC. Analytical validity of the assay was established in a clinical laboratory environment. The frequency of detecting transcripts was compared to CTC enumeration using CellSearch® in an independent data set and survival associations were explored by concordance probability estimate (CPE).
Results and Limitations
Two or more genes were detected by PCR in 53% (51 of 97, 95% CI 43–63%) of patients, and unfavorable CTC counts (≥5cells) were seen in 46% (45 of 97, 95% CI 36–56%). Importantly, transcripts were detectable in 11 of 52 patients with favorable CTC counts (21%, 95% CI 8–35%). Transcript detection predicted overall survival in a proportional hazards model. Significantly, the predictive accuracy of RT-PCR detection in combination with CTC enumeration had a CPE of 0.752 (SE=0.038), although limited by the number of patients.
This validated RT-PCR assay detecting prostate-specific RNA in whole blood is prognostic for survival, and may assess patient risk complimentary with CellSearch CTC enumeration. Its clinical utility is being prospectively explored.
biomarker; circulating tumor cells; prostate cancer; prostate-specific markers
Patient-reported outcomes are increasingly used in routine outpatient cancer care to guide clinical decisions and enhance communication. Prior evidence suggests good patient compliance with reporting at scheduled clinic visits, but there is limited evidence about compliance with long-term longitudinal reporting between visits.
Patients and Methods
Patients receiving chemotherapy for lung, gynecologic, genitourinary, or breast cancer at a tertiary cancer center, with access to a home computer and prior e-mail experience, were asked to self-report seven symptomatic toxicities via the Web between visits. E-mail reminders were sent to participants weekly; patient-reported high-grade toxicities triggered e-mail alerts to nurses; printed reports were provided to oncologists at visits. A priori threshold criteria were set to determine if this data collection approach merited further development based on monthly (≥ 75% participants reporting at least once per month on average) and weekly compliance rates (60% at least once per week).
Between September 2006 and November 2010, 286 patients were enrolled (64% were women; 88% were white; median age, 58 years). Mean follow-up was 34 weeks (range, 2 to 214). On average, monthly compliance was 83%, and weekly compliance was 62%, without attrition until the month before death. Greater compliance was associated with older age and higher education but not with performance status. Compliance was greatest during the initial 12 weeks. Symptomatic illness and technical problems were rarely barriers to compliance.
Monthly compliance with home Web reporting was high, but weekly compliance was lower, warranting strategies to enhance compliance in routine care settings.
To update eligibility and outcome measures in trials that evaluate systemic treatment for patients with progressive prostate cancer and castrate levels of testosterone.
A committee of investigators experienced in conducting trials for prostate cancer defined new consensus criteria by reviewing previous criteria, Response Evaluation Criteria in Solid Tumors (RECIST), and emerging trial data.
The Prostate Cancer Clinical Trials Working Group (PCWG2) recommends a two-objective paradigm: (1) controlling, relieving, or eliminating disease manifestations that are present when treatment is initiated and (2) preventing or delaying disease manifestations expected to occur. Prostate cancers progressing despite castrate levels of testosterone are considered castration resistant and not hormone refractory. Eligibility is defined using standard disease assessments to authenticate disease progression, prior treatment, distinct clinical subtypes, and predictive models. Outcomes are reported independently for prostate-specific antigen (PSA), imaging, and clinical measures, avoiding grouped categorizations such as complete or partial response. In most trials, early changes in PSA and/or pain are not acted on without other evidence of disease progression, and treatment should be continued for at least 12 weeks to ensure adequate drug exposure. Bone scans are reported as “new lesions” or “no new lesions,” changes in soft-tissue disease assessed by RECIST, and pain using validated scales. Defining eligibility for prevent/delay end points requires attention to estimated event frequency and/or random assignment to a control group.
PCWG2 recommends increasing emphasis on time-to-event end points (ie, failure to progress) as decision aids in proceeding from phase II to phase III trials. Recommendations will evolve as data are generated on the utility of intermediate end points to predict clinical benefit.
Personalized cancer medicine requires the development of tumor-specific biomarkers to optimize selection of targeted therapies and to better assess response to therapy. Current efforts in several tumor types have shown that patients in whom circulating tumor cells (CTCs) are detected have an inferior prognosis relative to those in whom CTCs are not detected and that the elimination or decrease of CTCs following treatment is associated with improved clinical outcomes. Technological advances in the detection, isolation, capture, and characterization of CTCs from phlebotomy samples obtained in a routine clinical practice setting have enabled the evaluation of different CTC biomarkers. Unmet needs in cancer diagnosis and treatment where CTC biomarkers have been studied include determining prognosis, assessing the effects of treatment, and as a source of tumor for the biologic identification and characterization of determinants to predict sensitivity to one form of treatment versus another and to understand mechanisms of treatment resistance.
At present, there is no single definition of a CTC and no single CTC “biomarker.” Rather, multiple assays (tests) are in development for CTC biomarkers. However, before the role of any biomarker in medical decision making can be determined, it is essential that the assays used to measure the biomarker are analytically validated in a sequence of trials to generate the evidence to support the biomarker’s use in the given context of use. It is against this background that this review focuses on the process of developing CTC biomarker assays, with the objective of outlining the necessary steps to qualify specific CTC tests for medical decision making in clinical practice or drug development. The potential for point-of-care tests is clear.
Circulating tumor cells; biomarker; regulatory qualification; personalized medicine
A critical challenge in the development of new molecularly targeted anticancer drugs is the identification of predictive biomarkers and the concurrent development of diagnostics for these biomarkers. Developing matched diagnostics and therapeutics will require new clinical trial designs and methods of data analysis. The use of adaptive design in phase III trials may offer new opportunities for matched diagnosis and treatment because the size of the trial can allow for subpopulation analysis. We present an adaptive phase III trial design that can identify a suitable target population during the early course of the trial, enabling the efficacy of an experimental therapeutic to be evaluated within the target population as a later part of the same trial. The use of such an adaptive approach to clinical trial design has the potential to greatly improve the field of oncology and facilitate the development of personalized medicine.
Unmet needs in prostate cancer drug development and patient management are the ability to monitor treatment benefit and to identify the target of interest in a tumor at the time treatment is being considered. This review focuses on establishing analytical valid biomarkers for specific contexts of use in patients with castration-resistant prostate cancer (CRPC), emphasizing a biomarker currently in clinical use, circulating tumor cells (CTC). The Oncology Biomarker Qualification Initiative provides a road map for these investigations, which, if followed, will facilitate the incorporation of these types of assays into clinical decision-making.
CTC enumeration at baseline and post-treatment is prognostic of survival, with no threshold effect, and the shedding of cells into the circulation represents an intrinsic property of the tumor, distinct from extent of disease. The clinical utility of monitoring CTC changes with treatment as an efficacy-response surrogate biomarker of survival is currently being tested in large phase III trials with the novel antiandrogen therapies abiraterone acetate and MDV3100.
Molecular biomarkers can be characterized in CTC as potential predictive biomarkers of tumor sensitivity to a therapeutic modality. Additionally, we discuss novel technologies to enrich and characterize CTC from more patients, and the potential clinical uses of CTC's in determining prognosis and monitoring treatment effects, and as a source of tissue to identify predictive markers of drug sensitivity to guide treatment selection. Prospective studies, designed around the biomarker itself and the specific clinical context for which it is applied, are needed to further assess the role of these and novel markers in clinical practice.
Ipilimumab is a fully human monoclonal antibody that binds cytotoxic T-lymphocyte antigen 4 to enhance antitumour immunity. Our aim was to assess the use of ipilimumab after radiotherapy in patients with metastatic castration-resistant prostate cancer that progressed after docetaxel chemotherapy.
We did a multicentre, randomised, double-blind, phase 3 trial in which men with at least one bone metastasis from castration-resistant prostate cancer that had progressed after docetaxel treatment were randomly assigned in a 1:1 ratio to receive bone-directed radiotherapy (8 Gy in one fraction) followed by either ipilimumab 10 mg/kg or placebo every 3 weeks for up to four doses. Non-progressing patients could continue to receive ipilimumab at 10 mg/kg or placebo as maintenance therapy every 3 months until disease progression, unacceptable toxic effect, or death. Patients were randomly assigned to either treatment group via a minimisation algorithm, and stratified by Eastern Cooperative Oncology Group performance status, alkaline phosphatase concentration, haemoglobin concentration, and investigator site. Patients and investigators were masked to treatment allocation. The primary endpoint was overall survival, assessed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT00861614.
From May 26, 2009, to Feb 15, 2012, 799 patients were randomly assigned (399 to ipilimumab and 400 to placebo), all of whom were included in the intention-to-treat analysis. Median overall survival was 11·2 months (95% CI 9·5–12·7) with ipilimumab and 10·0 months (8·3–11·0) with placebo (hazard ratio [HR] 0·85, 0·72–1·00; p=0·053). However, the assessment of the proportional hazards assumption showed that it was violated (p=0·0031). A piecewise hazard model showed that the HR changed over time: the HR for 0–5 months was 1·46 (95% CI 1·10–1·95), for 5–12 months was 0·65 (0·50–0·85), and beyond 12 months was 0·60 (0·43–0·86). The most common grade 3–4 adverse events were immune-related, occurring in 101 (26%) patients in the ipilimumab group and 11 (3%) of patients in the placebo group. The most frequent grade 3–4 adverse events included diarrhoea (64 [16%] of 393 patients in the ipilimumab group vs seven [2%] of 396 in the placebo group), fatigue (40 [11%] vs 35 [9%]), anaemia (40 [10%] vs 43 [11%]), and colitis (18 [5%] vs 0). Four (1%) deaths occurred because of toxic effects of the study drug, all in the ipilimumab group.
Although there was no significant difference between the ipilimumab group and the placebo group in terms of overall survival in the primary analysis, there were signs of activity with the drug that warrant further investigation.
J591 is a monoclonal antibody that targets the external domain of the prostate-specific membrane antigen (PSMA). Besides prostate cancer cells, it also targets the neovasculature of non-prostate solid tumors. We provide an analysis of the antibody mass-dose dependency of lesion uptake and normal tissue retention, together with an assessment of lesion detectability using 111In-J591 imaging, compared with conventional imaging in patients with a variety of solid tumors.
Twenty patients in six cohorts received fixed amounts (5, 10, 20, 40, 60, and 100 mg) of J591 in a phase I trial. A maximum of four administrations per patient was given, with each administration separated by 3 weeks. All antibody administrations included 370 MBq (10 mCi) of 111In labeled to 2 mg of J591 via the chelating agent DOTA. Three whole body (WB) gamma camera scans with at least one SPECT scan, along with multiple WB count-rate measurements and blood samples, were obtained for all patients. The effect of escalating antibody mass on lesion uptake and normal tissue retention was evaluated using lesion, liver, serum, and WB residence times and ratios thereof for each treatment cycle. Lesion detectability using 111In-J591 imaging was compared to the standard imaging on a lesion-by-lesion basis.
A total of 170 lesions in 20 patients were detected by standard or 111In-J591 imaging. 111In-J591 targeted both skeletal and soft tissue diseases in all tumor types. 111In-J591 imaging identified 74% (20/27) of skeletal lesions, 53% (18/34) of nodes, and 64% (70/109) of other soft tissue/organ lesions. There was increasing 111In-J591 uptake in lesions with increasing antibody mass-dose, coupled with decreasing retention in the liver for increments up to 20 mg, and no significant change at higher antibody mass.
Radiolabeled J591 antibody has potential as a targeting agent for solid tumor vasculature and lesion detection. Bone and soft tissue lesions arising from tumors of diverse origin were targeted by the anti-PSMA antibody J591. For the detection of lesions in these tumors by J591 antibody scans, an antibody mass of 20 mg is adequate. The optimal time of imaging is 5 to 7 days post-injection.
J591 antibody; Solid tumor; Neovasculature; Lesion detectability; Biodistribution
Given the bone tropism of prostate cancer, conventional imaging modalities poorly identify or quantify metastatic disease. 89Zr-huJ591 positron emission tomography (PET) imaging was performed in patients with metastatic prostate cancer to analyze and validate this as an imaging biomarker for metastatic disease. The purpose of this initial study was to assess safety, biodistribution, normal organ dosimetry, and optimal imaging time post-injection for lesion detection.
Ten patients with metastatic prostate cancer received 5 mCi of 89Zr-huJ591. Four whole-body scans with multiple whole-body count rate measurements and serum activity concentration measurements were obtained in all patients. Biodistribution, clearance, and lesion uptake by 89Zr-huJ591 immuno-PET imaging was analyzed and dosimetry was estimated using MIRD techniques. Initial assessment of lesion targeting of 89Zr-huJ591 was done. Optimal time for imaging post-injection was determined.
The dose was well tolerated with mild chills and rigors seen in two patients. The clearance of 89Zr-huJ591 from serum was bi-exponential with biological half-lives of 7 ± 4.5 h (range 1.1–14 h) and 62 ± 13 h (range 51–89 h) for initial rapid and later slow phase. Whole-body biological clearance was 219 ± 48 h (range 153–317 h). The mean whole-body and liver residence time was 78.7 and 25.6 h, respectively. Dosimetric estimates to critical organs included liver 7.7 ± 1.5 cGy/mCi, renal cortex 3.5 ± 0.4 cGy/mCi, and bone marrow 1.2 ± 0.2 cGy/mCi. Optimal time for patient imaging after injection was 7 ± 1 days. Lesion targeting of bone or soft tissue was seen in all patients. Biopsies were performed in 8 patients for a total 12 lesions, all of which were histologically confirmed as metastatic prostate cancer. One biopsy-proven lesion was not positive on 89Zr-huJ591, while the remaining 11 lesions were 89Zr-huJ591 positive. Two biopsy-positive nodal lesions were noted only on 89Zr-huJ591 study, while the conventional imaging modality was negative.
89Zr-huJ591 PET imaging of prostate-specific membrane antigen expression is safe and shows good localization of disease in prostate cancer patients. Liver is the critical organ for dosimetry, and 7 ± 1 days is the optimal imaging time. A larger study is underway to determine lesion detection in an expanded cohort of patients with metastatic prostate cancer.
89Zr-huJ591; J591 antibody; Prostate cancer; Radioimmunotherapy; Dosimetry
New therapeutic approaches for castration-resistant prostate cancer (CRPC) introduce new treatment dilemmas: how best to sequence these options to maximally benefit patients, what tests to perform before and after treatment to assess disease status, and how to interpret the test results and use them to guide treatment. New and specific end points for different classes of drugs are needed to provide the information to guide these treatment decisions. In 2008, the Prostate Cancer Working Group 2 consensus criteria for early-phase clinical trials redefined clinical trial end points as first, to control, relieve, or eliminate disease manifestations present when treatment is started and second, to prevent or delay future disease manifestations. Disease manifestations include prostate-specific antigen (PSA), soft-tissue disease (nodes and/or viscera), bone disease (most common site of spread), and symptoms. Recent US Food and Drug Administration (FDA) approvals for CRPC therapies have been based on the prevent/delay end points that reflect unequivocal benefit to a patient: prolongation of life or reduction in skeletal-related events (SREs). For the practicing oncologist, the control/relieve/eliminate outcomes should serve primarily to inform the decision of whether to continue therapy. In this review, we consider individual end points such as PSA, imaging, and patient-reported outcomes in the context of the control/relieve/eliminate and prevent/delay framework. We address the time-to-event end points of metastasis prevention, SRE, time to progression, and overall survival in the context of regulatory approvals. We also discuss circulating tumor cells measured with the CellSearch assay, recently cleared by the FDA for monitoring CRPC.
In 2005, the US Department of Defense, through the US Army Medical Research and Materiel Command, Office of the Congressionally Directed Medical Research Programs, created a funding mechanism to form a clinical trials consortium to conduct phase I and II studies in prostate cancer. This is the first report of the Prostate Cancer Clinical Trials Consortium (PCCTC).
Patients and Methods
The Department of Defense award supports a consortium of 10 prostate cancer research centers. Memorial Sloan-Kettering Cancer Center was awarded the Coordinating Center grant for the consortium and charged with creating an infrastructure to conduct early-phase multicenter clinical trials. Each participating center was required to introduce ≥ 1 clinical trial per year and maintain accrual of a minimum of 35 patients per year.
The PCCTC was launched in 2006 and now encompasses 10 leading prostate cancer research centers. Fifty-one trials have been opened, and 1386 patients have been accrued at member sites. Members share an online clinical trial management system for protocol tracking, electronic data capture, and data storage. A legal framework has been instituted, and standard operating procedures, an administrative structure, editorial support, centralized budgeting, and mechanisms for scientific review are established.
The PCCTC fulfills a congressional directive to create a clinical trials instrument dedicated to early-phase prostate cancer studies. The member institutions have built an administrative, informatics, legal, financial, statistical, and scientific infrastructure to support this endeavor. Clinical trials are open and accruing in excess of federally mandated goals.
Clinical consortium; Collaborative; Infrastructure; Phase I/II trial
BMS-641988 is an androgen receptor antagonist with increased potency relative to bicalutamide in both in vitro and in vivo prostate cancer models. A first-in-man phase I study was conducted to define the safety and tolerability of oral BMS-641988 in patients with castration-resistant prostate cancer (CRPC).
Doses were escalated from 5 to 150 mg based on discrete pharmacokinetic parameters in cohorts of 3 to 6 subjects. After establishing safety with 20 mg of BMS-641988 in the United States, a companion study was opened in Japan to assess differences in drug metabolism between populations.
Sixty-one men with CRPC were treated with daily BMS-641988. The pharmacokinetics of BMS-641988 and its active metabolites were proportional to dose. One patient experienced an epileptic seizure at a dose of 60 mg administered twice. Despite achieving target drug exposures, anti-tumor activity was limited to 1 partial response. Seventeen of 23 evaluable patients (74%) exhibited stable disease on imaging (median 15 weeks; range 8–32), and 10 of 61 patients (16%) achieved a ≥30%. decline in levels of prostate-specific antigen (PSA). Partial agonism was seen within the context of this study upon removal of the drug as evidenced by a decrease in PSA.
Although the clinical outcomes of predominantly stable disease and partial agonism were similar to what was observed in the preclinical evaluation of the compound, the limited anti-tumor activity of BMS-641988 at therapeutic dose levels coupled with an episode of seizure activity led to study closure.
To define the maximum tolerated dose (MTD), toxicities, and pharmacokinetics of 17-allylamino-17-demethoxygeldanamycin (17-AAG) when administered using continuous and intermittent dosing schedules.
Patients with progressive solid tumor malignancies were treated with 17-AAG using an accelerated titration dose escalation schema. The starting dose and schedule were 5 mg/m2 daily for 5 days with cycles repeated every 21 days. Dosing modifications based on safety, pharmacodynamic modeling, and clinical outcomes led to the evaluation of the following schedules: daily × 3 repeated every 14 days; twice weekly (days 1, 4, 8, and 11) for 2 weeks every 3 weeks; and twice weekly (days 1 and 4) without interruption. During cycle 1, blood was collected for pharmacokinetic and pharmacodynamic studies.
Fifty-four eligible patients were treated. The MTD was schedule dependent: 56 mg/m2 on the daily × 5 schedule; 112 mg/m2 on the daily × 3 schedule; and 220 mg/m2 on the days 1, 4, 8, and 11 every-21-day schedule. Continuous twice-weekly dosing was deemed too toxic because of delayed hepatotoxicity. Hepatic toxicity was also dose limiting with the daily × 5 schedule. Other common toxicities encountered were fatigue, myalgias, and nausea. This latter adverse effect may have been attributable, in part, to the DMSO-based formulation. Concentrations of 17-AAG above those required for activity in preclinical models could be safely achieved in plasma. Induction of a heat shock response and down-regulation of Akt and Raf-1 were observed in biomarker studies.
The MTD and toxicity profile of 17-AAG were schedule dependent. Intermittent dosing schedules were less toxic and are recommended for future phase II studies.
Persistence of ligand-mediated androgen receptor signaling has been documented in castration-resistant prostate cancers (CRPCs). Abiraterone acetate (AA) is a potent and selective inhibitor of CYP17, which is required for androgen biosynthesis in the testes, adrenal glands, and prostate tissue. This trial evaluated the efficacy and safety of AA in combination with prednisone to reduce the symptoms of secondary hyperaldosteronism that can occur with AA monotherapy.
Patients and Methods
Fifty-eight men with progressive metastatic CRPC who experienced treatment failure with docetaxel-based chemotherapy received AA (1,000 mg daily) with prednisone (5 mg twice daily). Twenty-seven (47%) patients had received prior ketoconazole. The primary outcome was ≥ 50% prostate-specific antigen (PSA) decline, with objective response by Response Evaluation Criteria in Solid Tumors (RECIST) criteria, and changes in Eastern Cooperative Oncology Group (ECOG) performance status (PS) and circulating tumor cell (CTC) numbers. Safety was also evaluated.
A ≥ 50% decline in PSA was confirmed in 22 (36%) patients, including 14 (45%) of 31 ketoconazole-naïve and seven (26%) of 27 ketoconazole-pretreated patients. Partial responses were seen in four (18%) of 22 patients with RECIST-evaluable target lesions. Improved ECOG PS was seen in 28% of patients. Median time to PSA progression was 169 days (95% CI, 82 to 200 days). CTC conversions with treatment from ≥ 5 to < 5 were noted in 10 (34%) of 29 patients. The majority of AA-related adverse events were grade 1 to 2, and no AA-related grade 4 events were seen.
AA plus prednisone was well tolerated, with encouraging antitumor activity in heavily pretreated CRPC patients. The incidence of mineralocorticoid-related toxicities (hypertension or hypokalemia) was reduced by adding low-dose prednisone. The combination of AA plus prednisone is recommended for phase III investigations.
We evaluated rapid androgen cycling in combination with docetaxel for men with progressive non-castrate prostate cancers.
Non-castrate patients with ≤ 6 months of hormones were eligible. Cohort 1 (63 patients ) received 6 28-day cycles of docetaxel (75 mg/m2), leuprolide and 7 days of topical testosterone. Cohort 2 (39 patients) received 9 21-day cycles of docetaxel (70 mg/m2), leuprolide and 3 days of testosterone. The primary endpoint was the proportion of patients at 18 months who achieved non -castrate testosterone levels (>150 ng/dl) and an undetectable PSA (≤ 0.05, ≤0.5, or ≤2.0 ng/ml with prior prostatectomy, radiotherapy, or no definitive therapy, respectively). Cytochrome P450 3A4 (CYP3A4) activity and docetaxel pharmacokinetics were evaluated.
A higher proportion of patients achieved the undetectable PSA outcome at 18 months in cohort 2 relative to cohort 1 (13% vs. 0%). The 16% incidence of febrile neutropenia was higher than observed in patients was castration-resistant disease, which may have been related to a 50% reduction in overall docetaxel clearance in the non-castrate group. There was no alteration in CYP3A4 activity (P=0.87) or docetaxel clearance (P=0.88) between cycles.
The undetectable PSA endpoint allows for a rapid screening of interventions for further study. Increasing the number of docetaxel cycles following a shorter period of testosterone repletion, and a longer duration of testosterone depletion, increased the proportion of men who achieved an undetectable PSA. The higher-than-expected incidence of febrile neutropenia may have been related to the reduced overall docetaxel clearance in patients with non-castrate vs castrate testosterone levels.
There is little consensus on a standard approach to analysing bone scan images. The Bone Scan Index (BSI) is predictive of survival in patients with progressive prostate cancer (PCa), but the popularity of this metric is hampered by the tedium of the manual calculation.
Develop a fully automated method of quantifying the BSI and determining the clinical value of automated BSI measurements beyond conventional clinical and pathologic features.
Design, setting, and participants
We conditioned a computer-assisted diagnosis system identifying metastatic lesions on a bone scan to automatically compute BSI measurements. A training group of 795 bone scans was used in the conditioning process. Independent validation of the method used bone scans obtained ≤3 mo from diagnosis of 384 PCa cases in two large population-based cohorts. An experienced analyser (blinded to case identity, prior BSI, and outcome) scored the BSI measurements twice. We measured prediction of outcome using pretreatment Gleason score, clinical stage, and prostate-specific antigen with models that also incorporated either manual or automated BSI measurements.
The agreement between methods was evaluated using Pearson’s correlation coefficient. Discrimination between prognostic models was assessed using the concordance index (C-index).
Results and limitations
Manual and automated BSI measurements were strongly correlated (ρ = 0.80), correlated more closely (ρ = 0.93) when excluding cases with BSI scores ≥10 (1.8%), and were independently associated with PCa death (p < 0.0001 for each) when added to the prediction model. Predictive accuracy of the base model (C-index: 0.768; 95% confidence interval [CI], 0.702–0.837) increased to 0.794 (95% CI, 0.727–0.860) by adding manual BSI scoring, and increased to 0.825 (95% CI, 0.754–0.881) by adding automated BSI scoring to the base model.
Automated BSI scoring, with its 100% reproducibility, reduces turnaround time, eliminates operator-dependent subjectivity, and provides important clinical information comparable to that of manual BSI scoring.
MDV3100 is a rationally-designed androgen receptor antagonist that blocks androgen receptor (AR) binding, nuclear translocation, and co-activator recruitment more effectively than the androgen receptor antagonists currently in use. MDV3100 is also unique in that it prevents DNA binding, induces apoptosis, and has no agonist activity when AR is overexpressed. Because growth of castration-resistant prostate cancer (CRPC) appears to depend upon continued androgen receptor signaling, we hypothesized that MDV3100 could be effective therapy for men with CRPC. Antitumor activity and safety were assessed in a phase 1-2 trial.
Eligible patients with progressive metastatic CRPC were enrolled in cohorts of 3-6 patients. Once the safety of a dose was established, cohorts were expanded to include at least 12 chemotherapy-naïve and 12 post-chemotherapy treated patients.
140 patients were treated with doses ranging from 30 to 600 mg daily. Positron emission tomography (PET) imaging to assess androgen receptor blockade showed decreased 18-fluorodihydrotestosterone binding at dosages of 60 mg/day and above. Antitumor effects were observed at all dosages including declines in serum PSA of 50% or more in 56% of patients, responses in soft tissue, stabilized bone disease, and conversion from unfavourable to favourable circulating tumour cell counts. The median time to progression was 47 weeks for radiological progression. The maximal tolerated dose for sustained treatment (>28 days) was 240 mg and the most common adverse event was dose-dependent fatigue, which generally resolved following dose reduction.
Encouraging antitumor activity on all outcomes assessed was observed for MDV3100 in both chemotherapy-naïve and post-chemotherapy patients with CRPC, establishing that patients with CRPC are not uniformly hormone-refractory. A phase 3 trial in patients with progressive disease after docetaxel treatment is underway.
To assess the efficacy of a single infusion of radiolabeled anti-prostate specific membrane antigen monoclonal antibody J591 (177Lu-J591) by PSA decline, measurable disease response, and survival.
In this dual-center phase II study, 2 cohorts with progressive metastatic castration-resistant prostate cancer received one dose of 177Lu-J591 (15 patients at 65 mCi/m2, 17 at 70 mCi/m2) with radionuclide imaging. Expansion cohort (n=15) received 70 mCi/m2 to verify response rate and examine biomarkers.
47 patients who progressed after hormonal therapies (55.3% also received prior chemotherapy) received 177Lu-J591. 10.6% experienced ≥ 50% decline in PSA, 36.2% experienced ≥ 30% decline, and 59.6% experienced any PSA decline following their single treatment. One of 12 with measurable disease experienced a partial radiographic response (8 with stable disease). Sites of prostate cancer metastases were targeted in 44 of 47 (93.6%) as determined by planar imaging. All experienced reversible hematologic toxicity with grade 4 thrombocytopenia occurring in 46.8% (29.8% received platelet transfusions) without significant hemorrhage. 25.5% experienced grade 4 neutropenia with 1 episode of febrile neutropenia. The phase I maximum tolerated dose (70 mCi/m2) resulted in more 30% PSA declines (46.9% vs 13.3%, p=0.048) and longer survival (21.8 vs 11.9 months, p=0.03), but also more grade 4 hematologic toxicity and platelet transfusions. No serious non-hematologic toxicity occurred. Those with poor PSMA imaging were less likely to respond.
A single dose of 177Lu-J591 was well-tolerated with reversible myelosuppression. Accurate tumor targeting and PSA responses were seen with evidence of dose-response. Imaging biomarkers appear promising.
Prostate Cancer; Prostate-specific Membrane Antigen; Radioimmunotherapy; Monoclonal Antibody
Activation of the androgen receptor is critical for prostate cancer growth at all points in the illness. Currently therapies targeting the androgen receptor, including androgen depletion approaches and antiandrogens, do not completely inhibit androgen receptor activity. Prostate cancer cells develop resistance to castration by acquiring changes such as AR overexpression that result in reactivation of the receptor. Based on understanding of these resistance mechanisms and androgen synthesis pathways, novel antiandrogens and androgen depleting agents have been tested. Notably, MDV3100, a novel antiandrogen designed for activity in prostate cancer model systems with overexpressed AR and, abiraterone acetate, a 17-α-hydroxylase/17,20 lyase inhibitor that blocks steroid biosynthesis in the adrenal gland and in the tumor, have demonstrated significant activity in early phase trials and are being tested in the phase III setting.
The authors' results provide a method for estimating accruals along the disease continuum, and for enabling design of trials appropriately powered to assess pain.
Contemporary tumor-directed therapies for metastatic castration-resistant prostate cancer (mCRPC) are approved to prolong life, but their effects on symptoms such as pain are less well understood as a result of the lack of analytically valid assessments of pain prevalence and severity, clinically meaningful definitions of therapeutic benefit, and methodologic standards of trial conduct. This study establishes pain characteristics in the mCRPC population using a PRO measure.
Materials and Methods:
Patients with prostate cancer participated in an anonymous survey at five US comprehensive cancer centers in the Prostate Cancer Clinical Trials Consortium that incorporated the Brief Pain Inventory (BPI), analgesic use, and interference with daily activities. Prevalence and severity of cancer-related pain and analgesic use were tabulated according to castration-resistant status and exposure to docetaxel chemotherapy.
Four hundred sixty-one patients with prostate cancer participated, of whom 147 had mCRPC involving bone (61% [89 of 147] docetaxel exposed, 39% [58 of 147] docetaxel naive). Pain of any level was more common among docetaxel-exposed versus docetaxel-naive patients with mCRPC (70% [62 of 89] v 38% [22 of 58], respectively; P < .001). BPI score ≥ 4 was reported by 38% (34 of 89) of docetaxel-pretreated and 24% (14 of 58) of docetaxel-naive patients with mCRPC; 40% of these patients with pain intensity ≥ 4 reported no current narcotic analgesic.
Pain prevalence and severity were higher in patients with prior docetaxel exposure. Analgesics were underutilized. These results provide a method for estimating accruals along the disease continuum, and for enabling design of trials appropriately powered to assess pain.
Beta-emitting bone-seeking radiopharmaceuticals have historically been administered for pain palliation while docetaxel prolongs life in metastatic castration-resistant prostate cancer (mCRPC). In combination, these agents simultaneously target the bone stroma and cancer cell to optimize anti-tumor effects. The toxicity and efficacy when each agent is combined at full, recommended doses, in a repetitive fashion is not well established.
Patients with progressive mCRPC and ≥3 bone lesions received 153Sm-EDTMP 1.0 mCi/kg every 9 weeks and docetaxel 75mg/m2 every 3 weeks. In the absence of unacceptable toxicity, patients were allowed to continue additional cycles, defined by 9 weeks of treatment, until intolerance or biochemical/radiographic progression.
Of 30 patients treated, 50% were taxane-naïve, 36.7% taxane-refractory, and 13.3% previously exposed to taxanes but not considered refractory. Patients received on average 2.5 cycles: 6.5 doses of docetaxel and 2.5 doses of 153Sm-EDTMP. Twelve (40%) demonstrated decline in prostate-specific antigen of ≥50%. Median progression-free survival (biochemical or radiographic) was 7.0 months and overall survival was 14.3 months. Nine patients (30%) did not recover platelet counts above 100 K/mm3 after a median of 3 cycles to allow for additional treatment, with four experiencing prolonged thrombocytopenia. The most common reasons for trial discontinuation were progressive disease and hematologic toxicity.
153Sm-EDTMP can be safely combined with docetaxel at full doses on an ongoing basis. Thrombocytopenia limited therapy for some patients; preliminary efficacy supports the strategy of combining a radiopharmaceutical with chemotherapy, an appealing strategy given the anticipated availability of alpha emitters that can prolong survival.
prostate cancer; 153Sm-EDTMP; docetaxel; chemotherapy; radiopharmaceutical
CT, fluorine 18 (18F) fluorodeoxyglucose PET, and 18F 16β-fluoro-5-dihydrotestosterone PET provided clinically relevant prognostic information in patients with bone metastases from castration-resistant prostate cancer, and imaging features such as CT lesion morphologic analysis, total number of bone lesions, and degree of androgen receptor expression were significantly associated with patient survival.
To compare the features of bone metastases at computed tomography (CT) to tracer uptake at fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and fluorine 18 16β-fluoro-5-dihydrotestosterone (FDHT) PET and to determine associations between these imaging features and overall survival in men with castration-resistant prostate cancer.
Materials and Methods
This is a retrospective study of 38 patients with castration-resistant prostate cancer. Two readers independently evaluated CT, FDG PET, and FDHT PET features of bone metastases. Associations between imaging findings and overall survival were determined by using univariate Cox proportional hazards regression.
In 38 patients, reader 1 detected 881 lesions and reader 2 detected 867 lesions. Attenuation coefficients at CT correlated inversely with FDG (reader 1: r = −0.3007; P < .001; reader 2: r = −0.3147; P < .001) and FDHT (reader 1: r = −0.2680; P = .001; reader 2: r = −0.3656; P < .001) uptake. The number of lesions on CT scans was significantly associated with overall survival (reader 1: hazard ratio [HR], 1.025; P = .05; reader 2: HR, 1.021; P = .04). The numbers of lesions on FDG and FDHT PET scans were significantly associated with overall survival for reader 1 (HR, 1.051–1.109; P < .001) and reader 2 (HR, 1.026–1.082; P ≤ .009). Patients with higher FDHT uptake (lesion with the highest maximum standardized uptake value) had significantly shorter overall survival (reader 1: HR, 1.078; P = .02; reader 2: HR, 1.092; P = .02). FDG uptake intensity was not associated with overall survival (reader 1, P = .65; reader 2, P = .38).
In patients with castration-resistant prostate cancer, numbers of bone lesions on CT, FDG PET, and FDHT PET scans and the intensity of FDHT uptake are significantly associated with overall survival.
© RSNA, 2013