A side-specific nomogram for extraprostatic extension may reduce the positive surgical margin rate in radical prostatectomy.

PURPOSE: Nomograms predicting side-specific extraprostatic extension (EPE) may be applied to reduce positive surgical margin (PSM) rates in patients planned for radical prostatectomy (RP). This study evaluates the impact of implementing an externally validated nomogram for side-specific EPE on PSM rate and degree of nerve-sparing. METHODS: In patients planned for RP, the side-specific nomogram predictions (based on MRI, ISUP grade group, and PSA density), with an advised threshold of 20% for safe nerve-sparing, were presented preoperatively to the urological surgeon. The surgeon completed a survey before RP about the planning with respect to side-specific nerve-sparing and change of management due to the result of the nomogram. PSM rates and degree of nerve-sparing were compared to a retrospective control group treated in the months prior to the introduction of the nomogram. RESULTS: A total of 100 patients were included, 50 patients in both groups representing 200 prostate lobes. Of the patients, 37% had histologically confirmed EPE, and 40% a PSM. In 12% of the 100 lobes planned after nomogram presentation, a change in management due to the nomogram was reported. A per-prostate lobe analysis of all the lobes showed comparable rates of full nerve-sparing (45% vs. 30%; p = 0.083) and lower rates of PSM on the lobes with histological EPE (45% vs. 85%; p < 0.05) in the intervention (nomogram) group versus the control group. CONCLUSION: Implementing a predictive nomogram for side-specific EPE in the surgical planning for nerve-sparing leads to lower rates PSM on the side of the histological EPE without compromising nerve-sparing.

Cross-resistance and drug sequence in prostate cancer.

The treatment landscape of advanced prostate cancer has widely expanded over the past years with androgen receptor signaling inhibitors (ARSIs) and taxane chemotherapy moving to earlier disease stages in the treatment of prostate cancer. With the increasing use of ARSIs in earlier disease stages, cross-resistance between treatments has emerged, which is a dominant impediment in current clinical practice. To overcome cross-resistance in the treatment of prostate cancer, it is of paramount importance to decipher the mechanisms of cross-resistance between ARSIs and between ARSIs and chemotherapy. Here, molecular mechanisms of resistance to the available therapies including androgen receptor (AR) splice variants, AR overexpression, AR mutations and glucocorticoid receptor upregulation are described. Based on these underlying mechanisms, clinical data of cross-resistance between ARSIs and chemotherapy have been reported. Only recently these data have been confirmed in prospective randomized trials. From these studies, it has become clear that sequential ARSI treatment has no place in the treatment of advanced prostate cancer due to emerging drug resistance. In addition, based on prospective evidence, we argue that it is worth considering an early switch to cabazitaxel treatment in case of lack of benefit on docetaxel regimen after an ARSI treatment. Based on these new insights from randomized trials, several recommendations for treatment sequence are proposed.

A bypass mechanism of abiraterone-resistant prostate cancer: Accumulating CYP17A1 substrates activate androgen receptor signaling.

BACKGROUND: Intratumoral steroidogenesis and its potential relevance in castration-resistant prostate cancer (CRPC) and in cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1)-inhibitor treated hormone-naïve and patients with CRPC are not well established. In this study, we tested if substrates for de novo steroidogenesis accumulating during CYP17A1 inhibition may drive cell growth in relevant preclinical models. METHODS: PCa cell lines and their respective CRPC sublines were used to model CRPC in vitro. Precursor steroids pregnenolone (Preg) and progesterone (Prog) served as substrate for de novo steroid synthesis. TAK700 (orteronel), abiraterone, and small interfering RNA (siRNA) against CYP17A1 were used to block CYP17A1 enzyme activity. The antiandrogen RD162 was used to assess androgen receptor (AR) involvement. Cell growth was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. AR-target gene expression was quantified by reverse transcription polymerase chain reaction (RT-PCR). Nuclear import studies using cells with green fluorescent protein (GFP)-tagged AR were performed to assess the potential of precursor steroids to directly activate AR. RESULTS: Preg and Prog stimulated cell proliferation and AR target gene expression in VCaP, DuCaP, LNCaP, and their respective CRPC sublines. The antiandrogen RD162, but not CYP17A1 inhibition with TAK700, abiraterone or siRNA, was able to block Preg- and Prog-induced proliferation. In contrast to TAK700, abiraterone also affected dihydrotestosterone-induced cell growth, indicating direct AR binding. Furthermore, Prog-induced AR translocation was not affected by treatment with TAK700 or abiraterone, while it was effectively blocked by the AR antagonist enzalutamide, further demonstrating the direct AR activation by Prog. CONCLUSION: Activation of the AR by clinically relevant levels of Preg and Prog accumulating in abiraterone-treated patients may act as a driver for CRPC. These data provide a scientific rationale for combining CYP17A1 inhibitors with antiandrogens, particularly in patients with overexpressed or mutated-AR.

Effects of prednisone on docetaxel pharmacokinetics in men with metastatic prostate cancer: A randomized drug-drug interaction study.

AIMS: Docetaxel has been approved for the treatment of metastatic prostate cancer in combination with prednisone. Since prednisone is known to induce the cytochrome P450 iso-enzyme CYP3A4, which is the main metabolizing enzyme of docetaxel in the liver, a potential drug-drug interaction may occur. In this prospective randomized pharmacokinetic cross-over study we investigated docetaxel exposure with concomitant prednisone, compared to docetaxel monotherapy in men with metastatic prostate cancer. METHODS: Patients scheduled to receive at least 6 cycles of docetaxel (75 mg/m2 ) and who gave written informed consent were randomized to receive either the 1st 3 cycles, or the last 3 consecutive cycles with prednisone (twice daily 5 mg). Pharmacokinetic blood sampling was performed during cycle 3 and cycle 6. Primary endpoint was difference in docetaxel exposure, calculated as area under the curve (AUC0-inf ) and analysed by means of a linear mixed model. Given the cross-over design the study was powered on 18 patients to answer the primary, pharmacokinetic, endpoint. RESULTS: Eighteen evaluable patients were included in the trial. Docetaxel concentration with concomitant prednisone (AUC0-inf 2784 ng*h/mL, 95% confidence interval 2436-3183 ng*h/mL) was similar to the concentration of docetaxel monotherapy (AUC0-inf 2647 ng*h/mL, 95% confidence interval 2377-2949 ng*h/mL). Exploratory analysis showed no toxicity differences between docetaxel monotherapy and docetaxel cycles with prednisone. CONCLUSION: No significant difference in docetaxel concentrations was observed. In addition, we found similar toxicity profiles in absence and presence of prednisone. Therefore, from a pharmacokinetic point of view, docetaxel may be administrated with or without prednisone.

Understanding taxanes in prostate cancer; importance of intratumoral drug accumulation.

BACKGROUND: Resistance to docetaxel is common in metastatic castration-resistant prostate cancer (mCRPC) and may be caused by sub-therapeutic intratumoral drug concentrations. Cabazitaxel demonstrated survival benefit in docetaxel-pretreated and docetaxel-refractory patients. In this study, we investigated whether the superior antitumor activity of cabazitaxel in mCRPC is explained by higher intratumoral cabazitaxel levels. Since recent studies suggest a reduced efficacy of docetaxel following treatment with novel androgen receptor (AR)-targeted agents, we also investigated taxane efficacy in an enzalutamide-resistant tumor model. METHODS: Intratumoral concentrations of docetaxel and cabazitaxel were correlated with antitumor activity in docetaxel-naïve, docetaxel-resistant, and enzalutamide-resistant patient-derived xenografts (PDXs) of prostate cancer. RESULTS: Intratumoral drug levels were negatively related to intrinsic and acquired resistance to docetaxel. Also, the observed stronger antitumor activity of cabazitaxel was associated with increased cumulative exposure and higher intratumoral of cabazitaxel concentrations in all PDXs. CONCLUSIONS: The superior antitumor activity of cabazitaxel in docetaxel- and enzalutamide-resistant tumors can be partly attributed to higher intratumoral drug concentrations. Especially for patients who are intrinsically resistant to docetaxel resulting from suboptimal intratumoral docetaxel concentrations, cabazitaxel may be the preferred chemotherapeutic agent. Prostate 76:927-936, 2016. © 2016 Wiley Periodicals, Inc.

Loss of SLCO1B3 drives taxane resistance in prostate cancer.

BACKGROUND: Both taxanes, docetaxel and cabazitaxel, are effective treatments for metastatic castration-resistant prostate cancer (mCRPC). However, resistance to taxanes is common. Our objective was to investigate mechanisms of taxane resistance in prostate cancer. METHODS: Two docetaxel-resistant patient-derived xenografts (PDXs) of CRPC were established (PC339-DOC and PC346C-DOC) in male athymic nude mice by frequent intraperitoneal administrations of docetaxel. Next-generation sequencing was performed on PDX tissue pre- and post-docetaxel resistance and gene expression profiles were compared. [(14)C]-docetaxel and [(14)C]-cabazitaxel uptake assays in vitro and cytotoxicity assays were performed to validate direct involvement of transporter genes in taxane sensitivity. RESULTS: Organic anion-transporting polypeptide (SLCO1B3), an influx transporter of docetaxel, was significantly downregulated in PC346C-DOC tumours. In accordance with this finding, intratumoural concentrations of docetaxel and cabazitaxel were significantly decreased in PC346C-DOC as compared with levels in chemotherapy-naive PC346C tumours. In addition, silencing of SLCO1B3 in chemo-naive PC346C resulted in a two-fold decrease in intracellular concentrations of both taxanes. Overexpression of SLCO1B3 showed higher sensitivity to docetaxel and cabazitaxel. CONCLUSIONS: The SLCO1B3 determines intracellular concentrations of docetaxel and cabazitaxel and consequently influences taxane efficacy. Loss of the drug transporter SLCO1B3 may drive taxane resistance in prostate cancer.

Irrefutable evidence for the use of docetaxel in newly diagnosed metastatic prostate cancer: results from the STAMPEDE and CHAARTED trials.

Androgen deprivation therapy (ADT) has been used in the treatment of metastatic prostate cancer since the first description of its hormonal dependence in 1941. In 2004, docetaxel chemotherapy became the mainstay of treatment in metastatic castration-resistant prostate cancer (mCRPC), following robust, albeit modest, survival benefit in two randomized phase 3 trials. The recently published CHAARTED trial was the first to show that combining ADT with docetaxel in men with hormone-naïve (hormone-sensitive) metastatic prostate cancer (mHSPC) yielded a remarkable overall survival benefit of 13.6 months as compared with ADT alone. In the current issue of The Lancet, James et al. report results of the STAMPEDE trial in men with high-risk locally advanced or metastatic prostate cancer initiating long-term hormone therapy. The combination of six cycles of docetaxel with ADT in men commencing long-term ADT demonstrated a similar OS benefit compared with standard of care (SOC) by a median of 10 months. Based on the consistency of the data and the firmness of the benefit provided, docetaxel in addition to ADT should be considered SOC for men with newly diagnosed mHSPC.

Associations between AR-V7 status in circulating tumour cells, circulating tumour cell count and survival in men with metastatic castration-resistant prostate cancer.

BACKGROUND: The interpretation of the presence of AR-V7 in circulating tumour cells (CTCs) in men with metastatic castration-resistant prostate cancer (mCRPC) remains to be elucidated. AR-V7 may hold promise as a predictive biomarker, but there may be prognostic impact of AR-V7 positivity as well. To investigate the clinical value of AR-V7, we determined whether AR-V7 detection in CTCs in patients with mCRPC is associated with CTC counts and survival. METHODS: Between December 2011 and January 2019, three prospective clinical trials collected clinical data of patients with mCRPC, who progressed after docetaxel and/or enzalutamide or abiraterone. Baseline (and follow-up) blood samples were withdrawn determining CTC count and AR-V7 expression. The majority of patients started cabazitaxel as the next line of treatment after AR-V7 characterisation. RESULTS: A total of 127 samples were evaluable for the analysis of CTC count versus AR-V7 status. Although an association was observed between AR-V7 and CTC count in all patients with mCRPC (p = 0.017), no such association was found in the prognostic unfavourable subgroup of patients with ≥5 CTCs. After adjusting for clinical prognostic factors, AR-V7 expression in CTCs was not associated with overall survival (hazard ratio = 1.33, 95% confidence interval = 0.81-2.15, p = 0.25). CONCLUSION: We found that AR-V7 expression in CTCs had no additional prognostic value in patients with mCRPC, mostly treated with cabazitaxel. In patients with mCRPC with a predefined worse prognosis of a higher CTC count (≥5), a predictive biomarker is an important unmet medical need. Prospective trials should investigate whether AR-V7 detection in CTCs may guide treatment selection for these adverse prognosis patients.

Prognostic factors in men with metastatic castration-resistant prostate cancer treated with cabazitaxel.

BACKGROUND: Treatment selection for men with metastatic castration-resistant prostate cancer (mCRPC) has become increasingly challenging with the introduction of novel therapies at earlier disease stages. The purpose of this study was to identify prognostic factors for overall survival (OS) and PSA response in patients with mCRPC treated with cabazitaxel. RESULTS: 224 mCRPC patients were included in the current analysis. In multivariable analysis, WHO performance status, baseline hemoglobin, alkaline phosphatase and albumin were all significantly associated with OS. Hemoglobin and alkaline phosphatase were significantly associated with PSA response. CONCLUSIONS: This study identified prognostic factors for OS and PSA response of men with mCRPC treated with cabazitaxel. In an increasingly complicated treatment landscape with several treatment options available our findings might serve to estimate the chance of survival of men qualifying for treatment with second-line chemotherapy in daily practice. Furthermore, these data can be used to risk-stratify patients in clinical trials. METHODS: We performed a post-hoc analysis of a randomized phase II trial of mCRPC patients treated with cabazitaxel. Cox and logistic regression models were used to investigate the influence of clinical and biochemical variables on OS and PSA response. Nomograms were developed to estimate the chance of PSA response and OS.

Effects of Budesonide on Cabazitaxel Pharmacokinetics and Cabazitaxel-Induced Diarrhea: A Randomized, Open-Label Multicenter Phase II Study.

Purpose: Forty-seven percent of patients in the pivotal trial of cabazitaxel reported diarrhea of any grade. Aiming to reduce the incidence of diarrhea, we studied the effects of budesonide on the grade of cabazitaxel-induced diarrhea during the first two treatment cycles.Experimental Design: Between December 2011 and October 2015, 246 metastatic castration-resistant prostate cancer patients were randomized to receive standard-of-care cabazitaxel 25 mg/m2 every 3 weeks plus prednisone 10 mg/day (group CABA) or same dose/schedule of cabazitaxel with concomitant budesonide 9 mg daily during the first two treatment cycles (group BUD). The occurrence of diarrhea was reported by physicians and by patients in a diary. χ2 tests were used to compare incidence numbers. An intention-to-treat principle was used.Results: In the phase II trial, 227 patients were evaluable. Grade 2-3 diarrhea occurred in 35 patients (15%) and grade 4 diarrhea was not reported. The incidence of grade 2-3 diarrhea was comparable in both treatment groups: 14 of 113 patients in group CABA (12%) versus 21 of 114 patients in group BUD (18%; P = 0.21). Seven patients were admitted to the hospital with diarrhea (n = 5 group CABA vs. n = 2 group BUD). PSA response was seen in 30% of patients and was not affected by budesonide coadministration (P = 0.29). Also, other toxicities were not affected by budesonide coadministration.Conclusions: The incidence of cabazitaxel-induced diarrhea was notably lower than reported in the TROPIC trial and appears manageable in routine clinical practice. Budesonide coadministration did not reduce the incidence or severity of cabazitaxel-induced diarrhea. Clin Cancer Res; 23(7); 1679-83. ©2016 AACR.

The Natural History and Outcome Predictors of Metastatic Castration-resistant Prostate Cancer.

CONTEXT: Biomarkers for the treatment of metastatic castration-resistant prostate cancer (mCRPC) are urgently needed by clinicians to facilitate treatment decisions. OBJECTIVE: To review current prognostic and predictive biomarkers in mCRPC. EVIDENCE ACQUISITION: We performed a nonsystematic review of the literature from 2004 to August 2016 by searching in Medline. Cross-matching references were used to search for additional articles. We reviewed clinical research and review articles written in the English language. EVIDENCE SYNTHESIS: Nomograms of prognostic factors (eg, albumin, lactate dehydrogenase) enable clinicians to estimate the prognosis of men with mCRPC. These prognostic tools may aid with when to trigger treatment, therapeutic monitoring, and follow-up. However, validated predictive biomarkers in mCRPC are still lacking. Androgen receptor (AR) splice variants (ie, AR-V7), gene fusions, and point mutations determined using liquid biopsies such as circulating tumor cells (CTCs) or cell-free DNA (cfDNA) are promising biomarkers that are the subject of ongoing research. Patient biomarkers (eg, neutrophil-to-lymphocyte ratio) are readily available and come with no extra cost but need further validation before their implementation in clinical practice. CONCLUSIONS: Determination of AR-V7 in CTCs is a big step towards a more personalized treatment approach in mCRPC. Genomic characterization of liquid biopsies such as CTCs, cfDNA, and circulating RNA are noninvasive tools to further personalize treatment in prostate cancer. Clinical parameters are readily available, but are derived from retrospective studies and should be interpreted with care. Only by conducting biomarker-driven studies, rather than large one-size-fits-all trials, will we be able to improve prostate cancer treatment. PATIENT SUMMARY: Several biomarkers are currently under investigation that may predict which patients will respond to specific therapies in the future of metastatic castration-resistant prostate cancer treatment.

Targeting the Androgen Receptor Confers In Vivo Cross-resistance Between Enzalutamide and Docetaxel, But Not Cabazitaxel, in Castration-resistant Prostate Cancer.

UNLABELLED: Treatment options for metastatic castration-resistant prostate cancer (CRPC) have evolved with the established benefit of the novel androgen receptor (AR)-targeted agents abiraterone and enzalutamide in the prechemotherapy setting. However, concerns regarding cross-resistance between the taxanes docetaxel and cabazitaxel and these AR-targeted agents have arisen, and the optimal drug treatment sequence is unknown. We investigated the in vivo efficacy of docetaxel and cabazitaxel in enzalutamide-resistant CRPC, and mechanisms of cross-resistance between these agents. Castrated mice harboring enzalutamide-resistant tumors and enzalutamide-naïve tumors were treated with docetaxel and cabazitaxel. Tumor growth kinetics, AR nuclear localization, AR-regulated gene expression, Ki67 expression, and serum levels of prostate-specific antigen, docetaxel, and cabazitaxel were analyzed. Docetaxel inhibited tumor growth, AR nuclear localization, and AR-regulated gene expression in enzalutamide-naïve tumors, but did not in enzalutamide-resistant tumors, demonstrating in vivo cross-resistance. By contrast, cabazitaxel remained highly effective in enzalutamide-resistant tumors and demonstrated superior antitumor activity compared to docetaxel, independent of the AR pathway. These findings demonstrate that the AR pathway is able to confer in vivo cross-resistance between enzalutamide and docetaxel, but not cabazitaxel, in CRPC. PATIENT SUMMARY: We found reduced efficacy of docetaxel, but not cabazitaxel, in enzalutamide-resistant prostate cancer.

Efficacy of Cabazitaxel in Castration-resistant Prostate Cancer Is Independent of the Presence of AR-V7 in Circulating Tumor Cells.

BACKGROUND: Androgen receptor splice variant 7 (AR-V7) in circulating tumor cells (CTCs) from patients with metastatic castration-resistant prostate cancer (mCRPC) was recently demonstrated to be associated with resistance to abiraterone and enzalutamide. Cabazitaxel might, however, remain effective in AR-V7-positive patients. OBJECTIVE: To investigate the association between AR-V7 expression in CTCs and resistance to cabazitaxel. DESIGN, SETTING, AND PARTICIPANTS: We selected patients with mCRPC from the multicenter, randomized, phase 2, randomized, open-label, multicenter study in mCRPC on the pharmacodynamic effects of budesonide on cabazitaxel (Jevtana) (CABARESC). Before the start of the first and third cabazitaxel cycle, CTCs were enumerated using the CellSearch System. In patients with ≥10 CTCs in 7.5 ml blood at baseline, the expression of AR-V7 was assessed by quantitative polymerase chain reaction. OUTCOME MEASURES AND STATISTICAL ANALYSIS: The primary end point was the association between the AR-V7 status and the CTC response rate (decrease to fewer than five CTCs in 7.5 ml blood during treatment). Secondary end points were the prostate-specific antigen (PSA) response rate (RR) and overall survival (OS). Analyses were performed using chi-square and log-rank tests. RESULTS AND LIMITATIONS: AR-V7 was detected in 16 of 29 patients (55%) with ≥10 CTCs and was more frequently found in abiraterone pretreated patients (5 of 5 [100%] treated vs 7 of 20 [35%] untreated; p=0.009). We found no differences in CTC and PSA RRs. The presence of AR-V7 in CTCs was not associated with progression-free survival (hazard ratio [HR]: 0.8; 95% confidence interval [CI], 0.4-1.8) or overall survival (HR 1.6; 95% CI, 0.6-4.4). CONCLUSIONS: The response to cabazitaxel seems to be independent of the AR-V7 status of CTCs from mCRPC patients. Consequently, cabazitaxel might be a valid treatment option for patients with AR-V7-positive CTCs. PATIENT SUMMARY: Tools are needed to select specific treatments for specific patients at specific times. The presence of the gene AR-V7 in CTCs has been associated with resistance to anti-androgen receptor treatments. We investigated whether this holds true for cabazitaxel, but we found cabazitaxel to be effective independent of the presence of AR-V7.

Initial biopsy Gleason score as a predictive marker for survival benefit in patients with castration-resistant prostate cancer treated with docetaxel: data from the TAX327 study.

BACKGROUND: Since 2004, docetaxel has been the standard first-line systemic therapy for patients with metastatic castration-resistant prostate cancer (mCRPC). With abiraterone recently becoming available in the predocetaxel setting, it is warranted to identify subgroups of patients who may obtain the greatest benefit from docetaxel and particularly qualify for receiving docetaxel as first-line treatment for mCRPC. OBJECTIVE: We aimed to identify factors that could characterize subgroups of patients who obtain the greatest benefit from the use of docetaxel. DESIGN, SETTING, AND PARTICIPANTS: TAX327 was multinational, randomized, phase 3 study that was conducted from 2000 to 2002 in 1006 men with mCRPC. INTERVENTION: Patients were randomized to receive docetaxel every 3 wk (D3), weekly docetaxel (D1), or mitoxantrone every 3 wk (M3), each with prednisone. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We investigated whether patients with poorly differentiated tumors (Gleason score ≥7) at diagnosis had greater benefit from D3 compared with M3 than patients with better differentiated tumors (Gleason score ≤6). Using a Cox model, we compared overall survival (OS) between the treatment groups within each subgroup of Gleason score. RESULTS AND LIMITATIONS: The TAX 327 data showed that the OS benefit of D3 versus M3 was greater in patients with high-grade tumors (median OS: 18.9 vs 14.5 mo; p=0.009) than in patients with low-grade tumors (median OS: 21.6 vs 20.7 mo; p=0.674). Limitations of a retrospective analysis apply. CONCLUSIONS: The survival benefit obtained with docetaxel is most pronounced in patients with high-Gleason-score tumors (Gleason ≥7). In a time of shifting paradigms in mCRPC, with abiraterone becoming available prior to docetaxel chemotherapy, Gleason score may help in selecting patients who obtain the greatest benefit from docetaxel as first-line treatment for mCRPC. Prospective validation of these findings is warranted.