Abiraterone acetate plus prednisolone with or without enzalutamide for patients with metastatic prostate cancer starting androgen deprivation therapy: final results from two randomised phase 3 trials of the STAMPEDE platform protocol.

BACKGROUND: Abiraterone acetate plus prednisolone (herein referred to as abiraterone) or enzalutamide added at the start of androgen deprivation therapy improves outcomes for patients with metastatic prostate cancer. Here, we aimed to evaluate long-term outcomes and test whether combining enzalutamide with abiraterone and androgen deprivation therapy improves survival. METHODS: We analysed two open-label, randomised, controlled, phase 3 trials of the STAMPEDE platform protocol, with no overlapping controls, conducted at 117 sites in the UK and Switzerland. Eligible patients (no age restriction) had metastatic, histologically-confirmed prostate adenocarcinoma; a WHO performance status of 0-2; and adequate haematological, renal, and liver function. Patients were randomly assigned (1:1) using a computerised algorithm and a minimisation technique to either standard of care (androgen deprivation therapy; docetaxel 75 mg/m2 intravenously for six cycles with prednisolone 10 mg orally once per day allowed from Dec 17, 2015) or standard of care plus abiraterone acetate 1000 mg and prednisolone 5 mg (in the abiraterone trial) orally or abiraterone acetate and prednisolone plus enzalutamide 160 mg orally once a day (in the abiraterone and enzalutamide trial). Patients were stratified by centre, age, WHO performance status, type of androgen deprivation therapy, use of aspirin or non-steroidal anti-inflammatory drugs, pelvic nodal status, planned radiotherapy, and planned docetaxel use. The primary outcome was overall survival assessed in the intention-to-treat population. Safety was assessed in all patients who started treatment. A fixed-effects meta-analysis of individual patient data was used to compare differences in survival between the two trials. STAMPEDE is registered with ClinicalTrials.gov (NCT00268476) and ISRCTN (ISRCTN78818544). FINDINGS: Between Nov 15, 2011, and Jan 17, 2014, 1003 patients were randomly assigned to standard of care (n=502) or standard of care plus abiraterone (n=501) in the abiraterone trial. Between July 29, 2014, and March 31, 2016, 916 patients were randomly assigned to standard of care (n=454) or standard of care plus abiraterone and enzalutamide (n=462) in the abiraterone and enzalutamide trial. Median follow-up was 96 months (IQR 86-107) in the abiraterone trial and 72 months (61-74) in the abiraterone and enzalutamide trial. In the abiraterone trial, median overall survival was 76·6 months (95% CI 67·8-86·9) in the abiraterone group versus 45·7 months (41·6-52·0) in the standard of care group (hazard ratio [HR] 0·62 [95% CI 0·53-0·73]; p<0·0001). In the abiraterone and enzalutamide trial, median overall survival was 73·1 months (61·9-81·3) in the abiraterone and enzalutamide group versus 51·8 months (45·3-59·0) in the standard of care group (HR 0·65 [0·55-0·77]; p<0·0001). We found no difference in the treatment effect between these two trials (interaction HR 1·05 [0·83-1·32]; pinteraction=0·71) or between-trial heterogeneity (I2 p=0·70). In the first 5 years of treatment, grade 3-5 toxic effects were higher when abiraterone was added to standard of care (271 [54%] of 498 vs 192 [38%] of 502 with standard of care) and the highest toxic effects were seen when abiraterone and enzalutamide were added to standard of care (302 [68%] of 445 vs 204 [45%] of 454 with standard of care). Cardiac causes were the most common cause of death due to adverse events (five [1%] with standard of care plus abiraterone and enzalutamide [two attributed to treatment] and one (<1%) with standard of care in the abiraterone trial). INTERPRETATION: Enzalutamide and abiraterone should not be combined for patients with prostate cancer starting long-term androgen deprivation therapy. Clinically important improvements in survival from addition of abiraterone to androgen deprivation therapy are maintained for longer than 7 years. FUNDING: Cancer Research UK, UK Medical Research Council, Swiss Group for Clinical Cancer Research, Janssen, and Astellas.

Abiraterone acetate plus prednisolone for metastatic patients starting hormone therapy: 5-year follow-up results from the STAMPEDE randomised trial (NCT00268476).

Abiraterone acetate plus prednisolone (AAP) previously demonstrated improved survival in STAMPEDE, a multiarm, multistage platform trial in men starting long-term hormone therapy for prostate cancer. This long-term analysis in metastatic patients was planned for 3 years after the first results. Standard-of-care (SOC) was androgen deprivation therapy. The comparison randomised patients 1:1 to SOC-alone with or without daily abiraterone acetate 1000 mg + prednisolone 5 mg (SOC + AAP), continued until disease progression. The primary outcome measure was overall survival. Metastatic disease risk group was classified retrospectively using baseline CT and bone scans by central radiological review and pathology reports. Analyses used Cox proportional hazards and flexible parametric models, accounting for baseline stratification factors. One thousand and three patients were contemporaneously randomised (November 2011 to January 2014): median age 67 years; 94% newly-diagnosed; metastatic disease risk group: 48% high, 44% low, 8% unassessable; median PSA 97 ng/mL. At 6.1 years median follow-up, 329 SOC-alone deaths (118 low-risk, 178 high-risk) and 244 SOC + AAP deaths (75 low-risk, 145 high-risk) were reported. Adjusted HR = 0.60 (95% CI: 0.50-0.71; P = 0.31 × 10-9 ) favoured SOC + AAP, with 5-years survival improved from 41% SOC-alone to 60% SOC + AAP. This was similar in low-risk (HR = 0.55; 95% CI: 0.41-0.76) and high-risk (HR = 0.54; 95% CI: 0.43-0.69) patients. Median and current maximum time on SOC + AAP was 2.4 and 8.1 years. Toxicity at 4 years postrandomisation was similar, with 16% patients in each group reporting grade 3 or higher toxicity. A sustained and substantial improvement in overall survival of all metastatic prostate cancer patients was achieved with SOC + abiraterone acetate + prednisolone, irrespective of metastatic disease risk group.

Independent prognostic impact of plasma NCOA2 alterations in metastatic castration-resistant prostate cancer.

BACKGROUND: The androgen receptor (AR) pathway-associated gene nuclear receptor coactivator 2 (NCOA2) has an established oncogenic role in early prostate cancer and likewise is a driver of metastatic disease and castration-resistant prostate cancer. However, its significance as a biomarker in metastatic castration-resistant prostate cancer (mCRPC), both alone and in conjunction with co-occurring AR alterations using a liquid biopsy approach has not been investigated. METHODS: Ninety-one patients were included in this study, (n = 68 receiving an androgen receptor pathway inhibitor and n = 23 receiving taxane chemotherapy). Up to 30 ml of peripheral blood was collected before commencing treatment from each patient. Plasma cell-free DNA, along with a matched germline sample, underwent targeted next-generation sequencing using a validated, highly sensitive in-house prostate cancer panel. Variants in AR and NCOA2 were identified and correlated with clinical outcomes. RESULTS: Plasma AR and NCOA2 aberrations were identified in 35% and 13% of the cohort, respectively, whilst 8% had concurrent AR and NCOA2 alterations. NCOA2 copy number gain and any NCOA2 aberration predicted for lower prostate-specific antigen (PSA) response rates. Likewise, median overall survival was shorter for NCOA2 gain (10.1 vs. 18.3 months; p = .004), remaining significant after adjusting for covariates including circulating tumor DNA fraction and tumor suppressor gene alterations. Importantly, dual AR and NCOA2 aberrations were also associated with inferior outcomes, including no PSA responses in patients treated with AR pathway inhibitors (0% vs. 64%; p = .02). CONCLUSIONS: These data highlight the importance of identifying multiple markers of AR pathway modulation in mCRPC and represent the first instance of the assessment of plasma NCOA2 status as a prognostic biomarker for standard-of-care therapies. Further assessment is warranted to determine if NCOA2 aberrations are a marker of primary resistance to AR pathway inhibitors.

Identification of novel oncogenic events occurring early in prostate carcinogenesis using purified autologous malignant and non-malignant prostate epithelial cells.

OBJECTIVE: To interrogate enriched prostate cancer cells and autologous non-malignant prostate epithelial cells from men with localized prostate cancer, in order to identify early oncogenic pathways. PATIENTS AND METHODS: We collected malignant and matched non-malignant prostatectomy samples from men with adenocarcinoma involving two or more contiguous areas in only one lobe of the prostate. Tissue samples from both lobes were subjected to digestion and single-cell suspensions were prepared. Epithelial cell adhesion molecule-positive cells from cancerous and contralateral non-malignant (control) samples were isolated using magnetic beads, ensuring uniform populations were obtained for each donor. Unbiased RNA sequencing analysis was used to measure gene expression and for detection of transcribed mutations or splice variants that were over- or under-represented in malignant prostate epithelial cells relative to autologous control prostate epithelial cells. RESULTS: From five patient samples we identified 17 genes that were altered in prostate cancer epithelial cells, with 82% of genes being downregulated. Three genes, TDRD1, ANGTL4, and CLDN3, were consistently upregulated in malignant tissue. Malignant cells from three of the five patients showed evidence of upregulated ERG signalling, however, only one of these contained a TMPRSS2-ERG rearrangement. We did not identify mutations, gene rearrangements, or splice variants that were consistent amongst the patients. CONCLUSIONS: Events occurring early in prostate cancer oncogenesis in these samples were characterized by a predominant downregulation of gene expression along with upregulation of TDRD1, ANGTL4 and CLDN3. No consistent mutations or splice variants were observed, but upregulation of ERG signalling was seen both in the presence and absence of the classic TMPRSS2-ERG rearrangement.

Circulating oestrogen receptor mutations and splice variants in advanced prostate cancer.

OBJECTIVE: To characterize circulating oestrogen receptor ( ER) mutants and splice variants in men with advanced prostate cancer. MATERIALS AND METHODS: Sequential blood samples were obtained from men with advanced prostate cancer, and from healthy controls. Blood-derived RNA samples were analysed using droplet digital PCR for the presence of six ERα mutations (E380Q, L536Q, Y537C, Y537S, Y537N and D538G), and six ERα and ERß splice variants (ERα-66, ERα-36, ERß1, ERß2, ERß4 & ERß5). RESULTS: A total of 94 samples were collected from 42 men with advanced prostate cancer. Four mutations (E380Q, L536Q, Y537S and D538G) and all six splice variants were detected in patient samples. Splice variants were detectable in non-cancer control samples. The presence of ER mutations was associated with bone metastases and castration resistance. ERß splice variant concentrations decreased after successive lines of treatment. CONCLUSIONS: The ER mutations were detectable in plasma from patients with advanced prostate cancer. ER splice variants were frequently detected in both men with and without prostate cancer.

Exploring the spectrum of late effects following radical orchidectomy for stage I testicular seminoma: a systematic review of the literature.

PURPOSE: Testicular seminomas occur in young men and are highly curable. Toxicities following treatment for men with extensive stage II-III seminomas may cause long-term morbidities. However, it is not clear whether the risk of late effects also increases following surgery for testis-confined seminoma. In this systematic review, we examined the available literature regarding the incidence of late effects in our target population of patients with stage I seminoma treated with orchidectomy alone. METHOD: Publications were identified through an electronic literature search using the MEDLINE, EMBASE and PsychInfo databases, identifying cohorts treated for stage I seminoma. Data on late effects were collected and classified as physical or psychological. RESULTS: Six hundred and four articles were screened to identify 100 studies. In the target population, available evidence suggests no increased risk of cardiovascular disease, metabolic syndrome, or renal dysfunction compared to the general population. Sperm counts were initially lower than an age-matched cohort; however, counts normalised when re-assessed 5 years later. Data were not specifically reported for the target population regarding bone health, second malignancy, hypogonadism, fertility and all psychological domains. Heterogeneity of study design and reporting methods contributed to uncertainty regarding the true incidence and clinical significance of late effects. CONCLUSIONS: The curability of stage I seminoma and the wide range of potential late effects of treatment suggest the need for long-term monitoring alongside standard cancer surveillance. Important data are needed on the prevalence of late effects, specifically related to testicular cancer survivors undergoing surveillance following orchidectomy. IMPLICATIONS FOR CANCER SURVIVORS: Awareness and screening for relevant late effects may prevent further morbidity in men treated for stage I seminoma.

Intraductal carcinoma of the prostate can evade androgen deprivation, with emergence of castrate-tolerant cells.

OBJECTIVE: To determine the relevance of intraductal carcinoma of the prostate (IDC-P) in advanced prostate cancer by first examining whether IDC-P was originally present in patients who later developed advanced prostate cancer and then using patient-derived xenografts (PDXs) to investigate the response of IDC-P to androgen deprivation therapy (ADT). MATERIALS AND METHODS: We conducted a retrospective pathology review of IDC-P in primary prostate biopsy or surgery specimens from 38 men who subsequently developed advanced prostate cancer. Overall survival was calculated using the Kaplan-Meier method. To demonstrate the response of IDC-P to ADT, we established PDXs from seven patients with familial and/or high-risk sporadic prostate cancer. After castration and testosterone restoration of host mice, we measured the volume and proliferation of IDC-P within PDX grafts. RESULTS: We found that IDC-P was a prominent feature in the primary prostate specimens, present in 63% of specimens and often co-existing with poorly differentiated adenocarcinoma. Overall survival was similar in patients with or without IDC-P. In the PDXs from all seven patients, IDC-P was identified and present at a similar volume to adenocarcinoma. Residual IDC-P lesions persisted after host castration and, similar to castrate-tolerant adenocarcinoma, testosterone restoration led to tumour regeneration. CONCLUSION: The study showed that IDC-P is prevalent in aggressive prostate cancer and contains cells that can withstand androgen deprivation. Thus, IDC-P appears functionally relevant in advanced prostate cancer. The presence of IDC-P may be a trigger to develop innovative clinical management plans.

Metastatic castration-resistant prostate cancer (CRPC): preclinical and clinical evidence for the sequential use of novel therapeutics.

With five novel therapies shown to improve survival in metastatic castration-resistant prostate cancer (CRPC) in the last 3 years, patients are now living longer and experiencing better quality of life. Since docetaxel became standard of care for men with symptomatic metastatic CRPC, three artificial treatment "spaces" have emerged for prostate cancer drug development: pre-docetaxel, docetaxel combinations, and following docetaxel. Multiple therapies are currently under development in both early and late stage CRPC. Additionally, the novel agents abiraterone, radium-223, cabazitaxel, and enzalutamide have all been approved in the post-docetaxel setting. Strategies for patient selection and treatment sequencing are therefore urgently required. In this comprehensive review, we will summarize the preclinical and clinical data available with regards to sequencing of the novel treatments for CRPC.

PTEN loss in circulating tumour cells correlates with PTEN loss in fresh tumour tissue from castration-resistant prostate cancer patients.

BACKGROUND: PTEN gene loss occurs frequently in castration-resistant prostate cancer (CRPC) and may drive progression through activation of the PI3K/AKT pathway. Here, we developed a novel CTC-based assay to determine PTEN status and examined the correlation between PTEN status in CTCs and matched tumour tissue samples. METHODS: PTEN gene status in CTCs was evaluated on an enrichment-free platform (Epic Sciences) by fluorescence in situ hybridisation (FISH). PTEN status in archival and fresh tumour tissue was evaluated by FISH and immunohistochemistry. RESULTS: Peripheral blood was collected from 76 patients. Matched archival and fresh cancer tissue was available for 48 patients. PTEN gene status detected in CTCs was concordant with PTEN status in matched fresh tissues and archival tissue in 32 of 38 patients (84%) and 24 of 39 patients (62%), respectively. CTC counts were prognostic (continuous, P=0.001). PTEN loss in CTCs associated with worse survival in univariate analysis (HR 2.05; 95% CI 1.17-3.62; P=0.01) and with high lactate dehydrogenase (LDH) in metastatic CRPC patients. CONCLUSIONS: Our results illustrate the potential use of CTCs as a non-invasive, real-time liquid biopsy to determine PTEN gene status. The prognostic and predictive value of PTEN in CTCs warrants investigation in CRPC clinical trials of PI3K/AKT-targeted therapies.

Simple prognostic score for metastatic castration-resistant prostate cancer with incorporation of neutrophil-to-lymphocyte ratio.

BACKGROUND: The neutrophil-to-lymphocyte ratio (NLR), a marker of inflammation, has been reported to be a poor prognostic indicator in prostate cancer. Here we explore the use of the NLR to establish a simple prognostic score for men with metastatic castration-resistant prostate cancer (mCRPC) treated with docetaxel. METHODS: In the training cohort, the NLR and other known prognostic variables were evaluated among a cohort of chemotherapy-naïve patients treated with thrice-weekly docetaxel at the Princess Margaret Cancer Centre. Significant prognostic variables identified by univariable Cox regression were evaluated by the area under the receiver operating characteristic curves. Multivariable Cox regression was then used to derive a prognostic score where 1 risk point was assigned for each significant variable. The model was externally validated in a cohort of patients treated at the Royal Marsden. RESULTS: Three hundred fifty-seven patients were analyzed in the training cohort. Median age was 71 years, 12% had liver metastasis, and median overall survival (OS) was 14.7 months. Liver metastases, hemoglobin <12 g/dL, alkaline phosphatase >2.0× upper limit of normal (ULN), lactate dehydrogenase >1.2× ULN, and NLR >3 were associated with significantly worse OS in multivariable analysis. Four risk categories were subsequently established with 0, 1, 2, and 3-5 points. Two-year OS rates for these categories were 43%, 37%, 12%, and 3%, respectively. Area under the curve for the training cohort was 0.78 (95% CI, 0.72-0.84) compared with 0.66 (95% CI, 0.58-0.74) for the 215 patients in the validation cohort. CONCLUSIONS: This simple risk score provides good prognostic and discriminatory accuracy for men with mCRPC.

Standard Versus Modified Ipilimumab, in Combination With Nivolumab, in Advanced Renal Cell Carcinoma: A Randomized Phase II Trial (PRISM).

PURPOSE: Ipilimumab (IPI), in combination with nivolumab (NIVO), is an approved frontline treatment option for patients with intermediate- or poor-risk advanced renal cell carcinoma (aRCC). We conducted a randomized phase II trial to evaluate whether administering IPI once every 12 weeks (modified), instead of once every 3 weeks (standard), in combination with NIVO, is associated with a favorable toxicity profile. METHODS: Treatment-naïve patients with clear-cell aRCC were randomly assigned 2:1 to receive four doses of modified or standard IPI, 1 mg/kg, in combination with NIVO (3 mg/kg). The primary end point was the proportion of patients with a grade 3-5 treatment-related adverse event (trAE) among those who received at least one dose of therapy. The key secondary end point was 12-month progression-free survival (PFS) in the modified arm compared with historical sunitinib control. The study was not designed to formally compare arms for efficacy. RESULTS: Between March 2018 and January 2020, 192 patients (69.8% intermediate/poor-risk) were randomly assigned and received at least one dose of study drug. The incidence of grade 3-5 trAEs was significantly lower among participants receiving modified versus standard IPI (32.8% v 53.1%; odds ratio, 0.43 [90% CI, 0.25 to 0.72]; P = .0075). The 12-month PFS (90% CI) using modified IPI was 46.1% (38.6 to 53.2). At a median follow-up of 21 months, the overall response rate was 45.3% versus 35.9% and the median PFS was 10.8 months versus 9.8 months in the modified and standard IPI groups, respectively. CONCLUSION: Rates of grade 3-5 trAEs were significantly lower in patients receiving modified versus standard IPI. Although 12-month PFS did not meet the prespecified efficacy threshold compared with historical control, informal comparison of treatment groups did not suggest any reduction in efficacy with the modified schedule.

Avelumab Combined with Stereotactic Ablative Body Radiotherapy in Metastatic Castration-resistant Prostate Cancer: The Phase 2 ICE-PAC Clinical Trial.

BACKGROUND: Immune checkpoint inhibitor monotherapy in metastatic castration-resistant prostate cancer (mCRPC) has produced modest results. High-dose radiotherapy may be synergistic with checkpoint inhibitors. OBJECTIVE: To evaluate the efficacy and safety of the PD-L1 inhibitor avelumab with stereotactic ablative body radiotherapy (SABR) in mCRPC. DESIGN, SETTING, AND PARTICIPANTS: From November 2017 to July 2019, this prospective phase 2 study enrolled 31 men with progressive mCRPC after at least one prior androgen receptor-directed therapy. Median follow-up was 18.0 mo. INTERVENTION: Avelumab 10 mg/kg intravenously every 2 wk for 24 wk (12 cycles). A single fraction of SABR (20 Gy) was administered to one or two disease sites within 5 d before the first and second avelumab treatments. OUTCOMES MEASUREMENTS AND STATISTICAL ANALYSIS: The primary endpoint was the disease control rate (DCR), defined as a confirmed complete or partial response of any duration, or stable disease/non-complete response/non-progressive disease for ≥6 mo (Prostate Cancer Clinical Trials Working Group 3-modified Response Evaluation Criteria in Solid Tumours version 1.1). Secondary endpoints were the objective response rate (ORR), radiographic progression-free survival (rPFS), overall survival (OS), and safety. DCR and ORR were calculated using the Clopper-Pearson exact binomial method. RESULTS AND LIMITATIONS: Thirty-one evaluable men were enrolled (median age 71 yr, 71% with ≥2 prior mCRPC therapy lines, 81% with >5 total metastases). The DCR was 48% (15/31; 95% confidence interval [CI] 30-67%) and ORR was 31% (five of 16; 95% CI 11-59%). The ORR in nonirradiated lesions was 33% (four of 12; 95% CI 10-65%). Median rPFS was 8.4 mo (95% CI 4.5-not reached [NR]) and median OS was 14.1 mo (95% CI 8.9-NR). Grade 3-4 treatment-related adverse events occurred in six patients (16%), with three (10%) requiring high-dose corticosteroid therapy. Plasma androgen receptor alterations were associated with lower DCR (22% vs 71%, p = 0.13; Fisher's exact test). Limitations include the small sample size and the absence of a control arm. CONCLUSIONS: Avelumab with SABR demonstrated encouraging activity and acceptable toxicity in treatment-refractory mCRPC. This combination warrants further investigation. PATIENT SUMMARY: In this study of men with advanced and heavily pretreated prostate cancer, combining stereotactic radiotherapy with avelumab immunotherapy was safe and resulted in nearly half of patients experiencing cancer control for 6 months or longer. Stereotactic radiotherapy may potentially improve the effectiveness of immunotherapy in prostate cancer.

Real-world incidence of symptomatic skeletal events and bone-modifying agent use in castration-resistant prostate cancer - an Australian multi-centre observational study.

INTRODUCTION: Bone metastases occur frequently in castration-resistant prostate cancer (CRPC) and may lead to skeletal-related events (SREs), including symptomatic skeletal events (SSEs). Bone-modifying agents (BMAs) delay SREs and SSEs. However, the real-world use of BMAs is debated given the absence of demonstrated survival advantage and potential adverse events (AEs). Our retrospective study examined BMA use and SSE rates in Australian patients with CRPC. METHODS: Patients with CRPC and bone metastases were identified from the electronic CRPC Australian Database. Patient characteristics, treatment patterns and AEs were analysed. Descriptive statistics reported baseline characteristics, SSE rates and BMA use. Comparisons between groups used t-tests and Chi-square analyses. Overall survival was calculated by the Kaplan-Meier method. RESULTS: A total of 532 eligible patients were identified with a median age of 73 years (range: 44-97 years). BMAs were prescribed in 232 men (46%), 183 of whom received denosumab. Patients receiving first-line docetaxel for CRPC were more likely to commence BMAs than those receiving abiraterone or enzalutamide (51% vs 31% vs 38%; p = 0.004). SSEs occurred in 148 men (28%), most commonly symptomatic lesions requiring intervention (75%). At the time of initial SSEs, only 28% were receiving BMAs. Patients treated at sites with lower BMA use (

Prognostic Impact of Total Plasma Cell-free DNA Concentration in Androgen Receptor Pathway Inhibitor-treated Metastatic Castration-resistant Prostate Cancer.

Total plasma cell-free DNA (cfDNA) levels were recently shown to be prognostic in two large phase III trials of taxane chemotherapy in metastatic castration-resistant prostate cancer (mCRPC). However, whether cfDNA concentration is predictive of treatment outcomes with androgen receptor pathway inhibitors (ARPIs) is unknown. We quantified plasma cfDNA levels at baseline (n = 74) and 4 weeks on treatment (n = 56) in a prospective cohort of mCRPC patients treated with the ARPIs abiraterone acetate or enzalutamide. Elevated total cfDNA concentration (log10) at both baseline (hazard ratio [HR] 5.5, p < 0.001) and week 4 (HR 7.5, p < 0.001) was a significant negative prognostic factor for overall survival (OS), a finding maintained after adjustment for plasma circulating tumour DNA fraction. Unexpectedly, a rise in cfDNA concentration from baseline to week 4 was also associated with significantly improved OS (HR 0.14, p = 0.003). Conversely, patients with ≥29.8% decrease in cfDNA from baseline (optimal cut-point) had significantly shorter median OS than the rest of the cohort (10.5 vs 25.7 mo, p = 0.03). Collectively, our findings point to the potential prognostic utility of quantifying cfDNA in mCRPC and in particular suggest that dynamic changes in total cfDNA levels may be a novel early predictive biomarker for therapeutic outcome in ARPI-treated patients. PATIENT SUMMARY: We measured the levels of total cell-free DNA (cfDNA) in the plasma of patients with metastatic prostate cancer prior to and 4 weeks after starting new hormonal drugs. We found that patients with higher levels of cfDNA or a higher proportion of tumour-derived DNA at baseline had worse outcomes on hormonal therapies. Similarly, higher levels of cfDNA at 4 weeks into therapy were also associated with worse outcomes. However, a rise in total cfDNA levels at 4 weeks compared with baseline was linked with better outcomes. Measuring changes in cfDNA concentration may be a useful and technically straightforward early way to predict how patients will respond to treatment in metastatic prostate cancer.

Prognostic Utility of a Whole-blood Androgen Receptor-based Gene Signature in Metastatic Castration-resistant Prostate Cancer.

BACKGROUND: The treatment paradigm for metastatic castration-resistant prostate cancer (mCRPC) has evolved significantly in recent years. Identifying predictive and/or prognostic biomarkers in the context of this rapidly expanding therapeutic armamentarium remains a pressing and unmet clinical need. OBJECTIVE: To develop a prognostic whole-blood gene signature for mCRPC patients. DESIGN, SETTING, AND PARTICIPANTS: As part of an ongoing prospective, multicentre biomarker research study (Australian Prostate Biomarker Alliance), we enrolled 115 mCRPC patients commencing chemotherapy (n = 34) or androgen receptor (AR) pathway inhibitors therapy (n = 81) and obtained pretreatment whole-blood samples in PAXgene RNA tubes. Gene expression was assessed using reverse transcription-polymerase chain reaction. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Gene transcripts correlating with overall survival (OS) at p < 0.10 in univariate Cox regression models were incorporated into a multigene signature. Kaplan-Meier survival estimates and multivariate analyses were used to assess association with clinical outcomes. Prognostic strength of the signature was estimated using a concordance probability estimate (CPE). RESULTS AND LIMITATIONS: Based on univariate analysis for OS, the following genes were incorporated into a multigene signature: AR splice variant 7 (AR-V7), and three androgen-regulated genes: GRHL2, HOXB13, and FOXA1. The number of positive transcripts clearly stratified survival outcomes (median OS: not reached vs 24.8 mo vs 16.2 mo for 0, 1, and ≥2 transcripts, respectively; p = 0.0052). Notably, this multigene signature retained prognostic significance on multivariable analysis (hazard ratio, 2.1; 95% confidence interval, 1.1-4.0; p = 0.019). Moreover, CPE for this model was 0.78, indicating strong discriminative capacity. Limitations include short follow-up time. CONCLUSIONS: Our data demonstrate the prognostic utility of a novel whole-blood AR-based signature in mCRPC patients commencing contemporary systemic therapies. Our pragmatic assay requires minimal processing, can be performed in most hospital laboratories, and could represent a key prognostic tool for risk stratification in mCRPC. PATIENT SUMMARY: We found that expression of certain genes associated with the androgen receptor could help determine how long men with advanced prostate cancer survive after starting modern drug therapies.

CX-5461 Sensitizes DNA Damage Repair-proficient Castrate-resistant Prostate Cancer to PARP Inhibition.

Monotherapy with PARP inhibitors is effective for the subset of castrate-resistant prostate cancer (CRPC) with defects in homologous recombination (HR) DNA repair. New treatments are required for the remaining tumors, and an emerging strategy is to combine PARP inhibitors with other therapies that induce DNA damage. Here we tested whether PARP inhibitors are effective for HR-proficient CRPC, including androgen receptor (AR)-null tumors, when used in combination with CX-5461, a small molecule that inhibits RNA polymerase I transcription and activates the DNA damage response, and has antitumor activity in early phase I trials. The combination of CX-5461 and talazoparib significantly decreased in vivo growth of patient-derived xenografts of HR-proficient CRPC, including AR-positive, AR-null, and neuroendocrine tumors. CX-5461 and talazoparib synergistically inhibited the growth of organoids and cell lines, and significantly increased the levels of DNA damage. Decreased tumor growth after combination therapy was maintained for 2 weeks without treatment, significantly increasing host survival. Therefore, combination treatment with CX-5461 and talazoparib is effective for HR-proficient tumors that are not suitable for monotherapy with PARP inhibitors, including AR-null CRPC. This expands the spectrum of CRPC that is sensitive to PARP inhibition.

Whole blood GRHL2 expression as a prognostic biomarker in metastatic hormone-sensitive and castration-resistant prostate cancer.

BACKGROUND: As potent systemic therapies transition earlier in the prostate cancer disease course, molecular biomarkers are needed to guide optimal treatment selection for metastatic hormone-sensitive prostate cancer (mHSPC). The value of whole blood RNA to detect candidate biomarkers in mHSPC remains largely undefined. METHODS: In this cohort study, we used a previously optimised whole blood reverse transcription polymerase chain reaction assay to assess the prognostic utility [measured by seven-month undetectable prostate-specific antigen (PSA) and time to castration-resistance (TTCR)] of eight prostate cancer-associated gene transcripts in 43 mHSPC patients. Transcripts with statistically significant associations (P<0.05) were further investigated in a metastatic castration-resistant prostate cancer (mCRPC) cohort (n=119) receiving contemporary systemic therapy, exploring associations with PSA >50% response (PSA50), progression-free survival (PFS) and overall survival (OS). Clinical outcomes were prospectively collected in a protected digital database. Kaplan-Meier estimates and multivariable Cox proportional-hazards models assessed associations between gene transcripts and clinical outcomes (mHSPC covariates: disease volume, docetaxel use and haemoglobin level; mCRPC covariates: prior exposure to chemotherapy or ARPIs, haemoglobin, performance status and presence of visceral disease). Follow-up was performed monthly during ARPI treatment, three-weekly during taxane chemotherapy, and three-monthly during androgen deprivation therapy (ADT) monotherapy. Serial PSA measurements were performed before each follow-up visit and repeat imaging was at the discretion of the investigator. RESULTS: Detection of circulating Grainyhead-like 2 (GRHL2) transcript was associated with poor outcomes in mHSPC and mCRPC patients. Detectable GRHL2 expression in mHSPC was associated with a lower rate of seven-month undetectable PSA levels (25% vs. 65%, P=0.059), and independently associated with shorter TTCR (HR 7.3, 95% CI: 1.5-36, P=0.01). In the mCRPC cohort, GRHL2 expression predicted significantly lower PSA50 response rates (46% vs. 69%, P=0.01), and was independently associated with shorter PFS (HR 3.1, 95% CI: 1.8-5.2, P<0.001) and OS (HR 2.9, 95% CI: 1.6-5.1, P<0.001). Associations were most apparent in patients receiving ARPIs. CONCLUSIONS: Detectable circulating GRHL2 was a negative prognostic biomarker in our mHSPC and mCRPC cohorts. These data support further investigation of GRHL2 as a candidate prognostic biomarker in metastatic prostate cancer, in addition to expanding efforts to better understand a putative role in therapeutic resistance to AR targeted therapies.

The MURAL collection of prostate cancer patient-derived xenografts enables discovery through preclinical models of uro-oncology.

Preclinical testing is a crucial step in evaluating cancer therapeutics. We aimed to establish a significant resource of patient-derived xenografts (PDXs) of prostate cancer for rapid and systematic evaluation of candidate therapies. The PDX collection comprises 59 tumors collected from 30 patients between 2012-2020, coinciding with availability of abiraterone and enzalutamide. The PDXs represent the clinico-pathological and genomic spectrum of prostate cancer, from treatment-naïve primary tumors to castration-resistant metastases. Inter- and intra-tumor heterogeneity in adenocarcinoma and neuroendocrine phenotypes is evident from bulk and single-cell RNA sequencing data. Organoids can be cultured from PDXs, providing further capabilities for preclinical studies. Using a 1 x 1 x 1 design, we rapidly identify tumors with exceptional responses to combination treatments. To govern the distribution of PDXs, we formed the Melbourne Urological Research Alliance (MURAL). This PDX collection is a substantial resource, expanding the capacity to test and prioritize effective treatments for prospective clinical trials in prostate cancer.

PARP inhibitor combinations in prostate cancer.

Polyadenosine-diphosphate-ribose polymerase (PARP) inhibitors cause deoxyribonucleic acid (DNA) damage that can be lethal to cells with deficient repair mechanisms. A number of PARP inhibitors are being tested as treatments for men with prostate cancer, both as monotherapies and in combinations that are based on purported synergies in treatment effect. While the initial single-agent development focused on men with identified deficiencies in DNA-repair pathways, broader patient populations are being considered for combination approaches. This review summarizes the current clinical development of PARP inhibitors and explores the rationale for novel combination strategies.