Aseem Anand

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.

Circulating Tumor Cell Number and Prognosis in Progressive Castration-Resistant Prostate Cancer

Purpose: The development of tumor-specific markers to select targeted therapies and to assess clinical outcome remains a significant area of unmet need. We evaluated the association of baseline circulating tumor cell (CTC) number with clinical characteristics and survival in patients with castrate metastatic disease considered for different hormonal and cytotoxic therapies. Experimental Design: CTC were isolated by immunomagnetic capture from 7.5-mL samples of blood from 120 patients with progressive clinical castrate metastatic disease. We estimated the probability of survival over time by the Kaplan-Meier method. The concordance probability estimate was used to gauge the discriminatory strength of the informative prognostic factors. Results: Sixty-nine (57%) patients had five or more CTC whereas 30 (25%) had two cells or less. Higher CTC numbers were observed in patients with bone metastases relative to those with soft tissue disease and in patients who had received prior cytotoxic chemotherapy relative to those who had not. CTC counts were modestly correlated to measurements of tumor burden such as prostate-specific antigen and bone scan index, reflecting the percentage of boney skeleton involved with tumor. Baseline CTC number was strongly associated with survival, without a threshold effect, which increased further when baseline prostate-specific antigen and albumin were included. Conclusions: Baseline CTC was predictive of survival, with no threshold effect. The shedding of cells into the circulation represents an intrinsic property of the tumor, distinct from extent of disease, and provides unique information relative to prognosis.

Phase II Multicenter Study of Abiraterone Acetate Plus Prednisone Therapy in Patients With Docetaxel-Treated Castration-Resistant Prostate Cancer

PURPOSE 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 > or = 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. RESULTS A > or = 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 > or = 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. CONCLUSION 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.

Circulating Tumor Cell Analysis in Patients with Progressive Castration-Resistant Prostate Cancer

Purpose: To better direct targeted therapies to the patients with tumors that express the target, there is an urgent need for blood-based assays that provide expression information on a consistent basis in real time with minimal patient discomfort. We aimed to use immunomagnetic-capture technology to isolate and analyze circulating tumor cells (CTC) from small volumes of peripheral blood of patients with advanced prostate cancer. Experimental Design: Blood was collected from 63 patients with metastatic prostate cancer. CTCs were isolated by the Cell Search system, which uses antibodies to epithelial cell adhesion marker and immunomagnetic capture. CTCs were defined as nucleated cells positive for cytokeratins and negative for CD45. Captured cells were analyzed by immunofluorescence, Papanicolau staining, and fluorescence in situ hybridization. Results: Most patients (65%) had 5 or more CTCs per 7.5 mL blood sample. Cell counts were consistent between laboratories (c = 0.99) and did not change significantly over 72 or 96 h of storage before processing (c = 0.99). Their identity as prostate cancer cells was confirmed by conventional cytologic analysis. Molecular profiling, including analysis of epidermal growth factor receptor (EGFR) expression, chromosome ploidy, and androgen receptor (AR) gene amplification, was possible for all prostate cancer patients with ≥5 CTCs. Conclusions: The analysis of cancer-related alterations at the DNA and protein level from CTCs is feasible in a hospital-based clinical laboratory. The alterations observed in EGFR and AR suggest that the methodology may have a role in clinical decision making.

Fluorescence in situ Hybridization Analysis of Circulating Tumor Cells in Metastatic Prostate Cancer

Purpose: To assess the feasibility of characterizing gene copy number alteration by fluorescence in situ hybridization (FISH) of circulating tumor cells (CTC) isolated using the CellSearch system in patients with progressive castration-resistant metastatic prostate cancer. Experimental Design: We used probe combinations that included the androgen receptor (AR) and MYC genes for FISH analysis of CTC samples collected from 77 men with castration-resistant metastatic prostate cancer. Results: High-level chromosomal amplification of AR was detected in 38% and relative gain of MYC in 56% of samples analyzed. No such abnormalities were detected in samples with CTC counts of <10, reflecting ascertainment difficulty in these lower count samples. Conclusion: The CTC isolated from our patient cohort present a very similar molecular cytogenetic profile to that reported for late-stage tumors and show that FISH analysis of CTC can be a valuable, noninvasive surrogate for routine tumor profiling. That as many as 50% of these patients have substantial amplification of the AR locus indicates that androgen signaling continues to play an important role in late-stage prostate cancer.

TMPRSS2-ERG Status in Circulating Tumor Cells as a Predictive Biomarker of Sensitivity in Castration-Resistant Prostate Cancer Patients Treated With Abiraterone Acetate

BACKGROUND Abiraterone acetate (AA) is an androgen biosynthesis inhibitor shown to prolong life in patients with castration-resistant prostate cancer (CRPC) already treated with chemotherapy. AA treatment results in dramatic declines in prostate-specific antigen (PSA) in some patients and no declines in others, suggesting the presence of molecular determinants of sensitivity in tumors. OBJECTIVE To study the role of transmembrane protease, serine 2 (TMPRSS2)-v-ets erythroblastosis virus E26 oncogene homolog (ERG) fusion, an androgen-dependent growth factor, in circulating tumor cells (CTCs) as a biomarker of sensitivity to AA. DESIGN, SETTING, AND PARTICIPANTS The predictive value of TMPRSS2-ERG status was studied in 41 of 48 men with postchemotherapy-treated CRPC enrolled in sequential phase 2 AA trials. INTERVENTION Patients received AA 1000 mg daily and continuously. MEASUREMENTS TMPRSS2-ERG status was characterized by a sensitive, analytically valid reverse transcription polymerase chain reaction assay in CTCs enriched from ethylene-diaminetetraacetic acid anticoagulated blood obtained prior to AA treatment. Outcomes were measured by PSA Working Group 1 criteria. RESULTS AND LIMITATIONS Standard procedures for specimen acquisition, processing, and testing using the validated TMPRSS2-ERG assay on a multiplex platform gave intra-assay and interassay coefficients of variation <7%. TMPRSS2-ERG fusion was present in 15 of 41 patients (37%), who had a median baseline CTC count of 17 (interquartile range: 7-103 cells per 7.5 ml). A PSA decline ≥50% was observed in 7 of 15 patients (47%) with the fusion and in 10 of 26 patients (38%) without the fusion. Although limited by the low number of patients, a posttherapy CTC count of less than five per 7.5 ml was prognostic for longer survival relative to a CTC count five or more. TMPRSS2-ERG status did not predict a decline in PSA or other clinical outcomes. CONCLUSIONS Molecular profiles of CTCs with an analytically valid assay identified the presence of the prostate cancer-specific TMPRSS2-ERG fusion but did not predict for response to AA treatment. This finding demonstrates the role of CTCs as surrogate tissue that can be obtained in a routine practice setting. TRIAL REGISTRATION ClinicalTrials.gov: NCT00474383 (COU-AA-003), NCT00485303 (COU-AA-004).

Circulating Prostate Tumor Cells Detected by Reverse Transcription-PCR in Men with Localized or Castration-Refractory Prostate Cancer: Concordance with CellSearch Assay and Association with Bone Metastases and with Survival

BACKGROUND Reverse transcription-PCR (RT-PCR) assays have been used for analysis of circulating tumor cells (CTCs), but their clinical value has yet to be established. We assessed men with localized prostate cancer or castration-refractory prostate cancer (CRPC) for CTCs via real-time RT-PCR assays for KLK3 [kallikrein-related peptidase 3; i.e., prostate-specific antigen (PSA)] and KLK2 mRNAs. We also assessed the association of CTCs with disease characteristics and survival. METHODS KLK3, KLK2, and PSCA (prostate stem cell antigen) mRNAs were measured by standardized, quantitative real-time RT-PCR assays in blood samples from 180 localized-disease patients, 76 metastatic CRPC patients, and 19 healthy volunteers. CRPC samples were also tested for CTCs by an immunomagnetic separation system (CellSearch; Veridex) approved for clinical use. RESULTS All healthy volunteers were negative for KLK mRNAs. Results of tests for KLK3 or KLK2 mRNAs were positive (> or =80 mRNAs/mL blood) in 37 patients (49%) with CRPC but in only 15 patients (8%) with localized cancer. RT-PCR and CellSearch CTC results were strongly concordant (80%-85%) and correlated (Kendall tau, 0.60-0.68). Among CRPC patients, KLK mRNAs and CellSearch CTCs were closely associated with clinical evidence of bone metastases and with survival but were only modestly correlated with serum PSA concentrations. PSCA mRNA was detected in only 7 CRPC patients (10%) and was associated with a positive KLK mRNA status. CONCLUSIONS Real-time RT-PCR assays of KLK mRNAs are highly concordant with CellSearch CTC results in patients with CRPC. KLK2/3-expressing CTCs are common in men with CRPC and bone metastases but are rare in patients with metastases diagnosed only in soft tissues and patients with localized cancer.

A whole-blood RNA transcript-based prognostic model in men with castration-resistant prostate cancer: a prospective study

BACKGROUND Survival for patients with castration-resistant prostate cancer is highly variable. We assessed the effectiveness of a whole-blood RNA transcript-based model as a prognostic biomarker in castration-resistant prostate cancer. METHODS Peripheral blood was prospectively collected from 62 men with castration-resistant prostate cancer on various treatment regimens who were enrolled in a training set at the Dana-Farber Cancer Institute (Boston, MA, USA) from August, 2006, to June, 2008, and from 140 patients with castration-resistant prostate cancer in a validation set from Memorial Sloan-Kettering Cancer Center (New York, NY, USA) from August, 2006, to February, 2009. A panel of 168 inflammation-related and prostate cancer-related genes was assessed with optimised quantitative PCR to assess biomarkers predictive of survival. FINDINGS A six-gene model (consisting of ABL2, SEMA4D, ITGAL, and C1QA, TIMP1, CDKN1A) separated patients with castration-resistant prostate cancer into two risk groups: a low-risk group with a median survival of more than 34·9 months (median survival was not reached) and a high-risk group with a median survival of 7·8 months (95% CI 1·8-13·9; p<0·0001). The prognostic utility of the six-gene model was validated in an independent cohort. This model was associated with a significantly higher area under the curve compared with a clinicopathological model (0·90 [95% CI 0·78-0·96] vs 0·65 [0·52-0·78]; p=0·0067). INTERPRETATION Transcriptional profiling of whole blood yields crucial prognostic information about men with castration-resistant prostate cancer. The six-gene model suggests possible dysregulation of the immune system, a finding that warrants further study. FUNDING Source MDX.

Androgen receptor expression is associated with prostate cancer-specific survival in castrate patients with metastatic disease

Study Type – Aetiology (case series)
 Level of Evidence 4

Analytic and Clinical Validation of a Prostate Cancer–Enhanced Messenger RNA Detection Assay in Whole Blood as a Prognostic Biomarker for Survival

BACKGROUND Biomarkers based on detecting prostate cancer (PCa)-specific transcripts in blood are associated with inferior outcomes, but their validation in a clinical context is lacking. OBJECTIVE To determine whether detecting enhanced transcripts for PCa in whole blood using an analytically valid assay has prognostic significance relative to circulating tumor cell (CTC) enumeration. DESIGN, SETTING, AND PARTICIPANTS The detection of KLK3, KLK2, HOXB13, GRHL2, and FOXA1 in whole blood by reverse transcription polymerase chain reaction (RT-PCR) was studied in 97 men with metastatic castration-resistant PCa (mCRPC) as a prognostic factor for overall survival. INTERVENTION The 2.5 ml 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 PCa-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% of patients (51 of 97; 95% confidence interval [CI], 43-63%), and unfavorable CTC counts (five of more cells) 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 (standard error: 0.038), although this was limited by the number of patients evaluated. CONCLUSIONS This validated RT-PCR assay detecting prostate-specific RNA in whole blood is prognostic for survival and may assess patient risk in tandem with CellSearch CTC enumeration. Its clinical utility is being prospectively explored.