Randomized Phase II Multicenter Trial of Abiraterone Acetate With or Without Cabazitaxel in the Treatment of Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Improving clinical outcomes with novel drug combinations to treat metastatic castration-resistant prostate cancer (mCRPC) is challenging. Preclinical studies showed cabazitaxel had superior antitumor efficacy compared with docetaxel. Gene expression profiling revealed divergent effects of these taxanes in cycling cells. mCRPC are RB deficient rendering them hypersensitive to taxanes. These data suggested that upfront treatment with cabazitaxel with abiraterone may affect therapeutic response. We designed a phase II randomized noncomparative trial of abiraterone acetate/prednisone (AAP) or AAP and cabazitaxel (AAP + C) in men with mCRPC to address this hypothesis.

METHODS

This trial of 81 men with mCRPC determined the radiographic progression-free survival (rPFS), prostate-specific antigen (PSA) progression-free survival, overall objective response, and safety of AAP or AAP + C. Equally allocated patients received AAP followed by switching to cabazitaxel upon radiographic progression (arm 1) or upfront with AAP + C (arm 2). Patients were stratified into high-/low-risk groups by the Halabi nomogram. Real-time assessment of RB status and circulating tumor cell (CTC) analysis to correlate with clinical outcomes was exploratory.

RESULTS

Both treatment arms were well-tolerated. Median rPFS in AAP was 6.4 months (95% CI, 3.8 to 10.6) and median overall survival (OS) 18.3 months (95% CI, 14.4 to 37.6), respectively. Fifty-six percent of patients showed ≥50% decline in PSA. Median rPFS in AAP + C was 14.8 months (95% CI, 10.6 to 16.4), and median OS 24.5 months (95% CI, 20.4 to 35.0). There was a ≥50% decline in PSA in 92.1% of men. Neither RB expression in pretherapy tumor biopsy, CTC, or tissue explants identified those who may benefit from AAP + C.

CONCLUSION

AAP + C was safe with improved rPFS, OS duration, and a higher proportion of PSA declines. This suggests that AAP + C given earlier rather than sequentially may benefit some men. Further work is needed to identify this population.

Genomic Portraits: Reflections into a Tumor's Response to Therapy

Well-annotated matched tissue specimens both before and after initiation of androgen receptor signaling inhibitors (ARSI) have revealed activation of unique signaling pathways and genomic signatures that identify a profile to guide therapy. A recent study represents the largest prospective biospecimen banking protocol to study mechanisms of resistance to ARSIs. See related article by Menssouri et al., p. 4504.

Evaluating Immune-Related Adverse Events Using PRO-CTCAE in a Phase II Study of Ipilimumab for Hormone-Sensitive Prostate Cancer

Introduction

 Use of the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) during chemotherapy is associated with decreased hospitalization rates, improved quality of life, and longer survival. Limited data exist on the benefit of this symptom assessment tool for monitoring immune-related adverse events (irAEs).

Methods

 We incorporated irAE-related items from the National Cancer Institute's (NCI) PRO-CTCAE in a trial evaluating ipilimumab in combination with androgen deprivation therapy in 16 patients with hormone-sensitive prostate cancer. For comparison, NCI's CTCAE version 4.0 was used by clinicians.

Results

 IrAE-related PRO-CTCAE surveys and matched CTCAEs (184 pairs) reporting abdominal pain, diarrhea, fatigue, anorexia, nausea, vomiting, rash, and pruritus were collected at each treatment administration and during follow-up. Fatigue, diarrhea, rash, and pruritus were the symptoms most frequently reported by both patients and clinicians. Agreement was lowest for pruritus (κ = 0.10) and highest for rash (κ = 0.64). IrAEs were more commonly reported and of higher grade with PRO-CTCAE scores compared with CTCAE grades.

Conclusion

 PRO-CTCAEs focused on irAEs capture the patient's immunotherapy experience while complementing the clinician's toxicity assessment measures. Further study is needed to assess PRO-CTCAE's utility in identifying and managing irAEs.

Immunotherapy in the Treatment of Localized Genitourinary Cancers

Importance

A true revolution in the management of advanced genitourinary cancers has occurred with the discovery and adoption of immunotherapy (IO). The therapeutic benefits of IO were recently observed not to be solely confined to patients with disseminated disease but also in select patients with localized and locally advanced genitourinary neoplasms.

Observations

KEYNOTE-057 demonstrated the benefit of pembrolizumab monotherapy for treating high-risk nonmuscle invasive bladder cancer unresponsive to bacillus Calmette-Guérin (BCG), resulting in recent US Food and Drug Administration approval. Furthermore, a current phase 3 trial (Checkmate274) demonstrated a disease-free survival benefit with the administration of adjuvant nivolumab vs placebo in muscle-invasive urothelial carcinoma after radical cystectomy. In addition, the recent highly publicized phase 3 KEYNOTE 564 trial demonstrated a recurrence-free survival benefit of adjuvant pembrolizumab in patients with high-risk localized/locally advanced kidney cancer.

Conclusions and Relevance

The adoption and integration of IO in the management of localized genitourinary cancers exhibiting aggressive phenotypes are becoming an emerging therapeutic paradigm. Clinical oncologists and scientists should become familiar with these trials and indications because they are likely to dramatically change our treatment strategies in the months and years to come.

An AI Predictive Model to Determine Who Benefits from ADT with Radiation: Working Smarter, Not Harder

Whether you are a surgical, medical, or radiation oncologist, the care goals remain the same, that is, achieving a durable treatment response. For patients with localized intermediate-risk prostate cancer undergoing radiation treatment, identifying those who would derive additional benefit from androgen deprivation therapy (ADT) is an ongoing challenge. To help physicians make this decision, prognostic risk scores have been derived from biobanked pathology specimens1-3 coupled with well-annotated clinical and imaging data from multiple phase III trials.

Immunotherapy combinations for metastatic castration-resistant prostate cancer - failed trials and future aspects

PURPOSE OF REVIEW

Immunotherapy, a treatment modality currently synonymous with immune checkpoint blockade remains a challenge for prostate cancer. Despite multiple phase 3 trials using checkpoint inhibitors in combinatorial approaches, there have been no benefits to date in overall survival or radiographic progression free survival. However, newer strategies prevail that are directed to a variety of unique cell surface antigens. These strategies include unique vaccines, chimeric antigen receptor (CAR) T, bispecific T cell engager platforms, and antibody-drug conjugates.

RECENT FINDINGS

New antigens are being targeted by various immunologic strategies. These antigens are pan-carcinoma as they may be expressed on a variety of cancers but remains effective targets for therapeutic attack.

SUMMARY

Immunotherapy with checkpoint inhibitors alone or in combination with a variety of agents such as chemotherapy, poly-ADP ribose polymerase (PARP) inhibitors or novel biologics have met with failure in the endpoints of overall survival (OS) and radiographic progresson-free survival (rPFS). Despite these efforts, other immunologic efforts to develop unique tumor-targeted strategies should be continued.

Expression and Therapeutic Targeting of TROP-2 in Treatment-Resistant Prostate Cancer

PURPOSE

Men with metastatic castration-resistant prostate cancer (mCRPC) frequently develop resistance to androgen receptor signaling inhibitor (ARSI) treatment; therefore, new therapies are needed. Trophoblastic cell-surface antigen (TROP-2) is a transmembrane protein identified in prostate cancer and overexpressed in multiple malignancies. TROP-2 is a therapeutic target for antibody-drug conjugates (ADC).

EXPERIMENTAL DESIGN

TROP-2 gene (TACSTD2) expression and markers of treatment resistance from prostate biopsies were analyzed using data from four previously curated cohorts of mCRPC (n = 634) and the PROMOTE study (dbGaP accession phs001141.v1.p1, n = 88). EPCAM or TROP-2-positive circulating tumor cells (CTC) were captured from peripheral blood for comparison of protein (n = 15) and gene expression signatures of treatment resistance (n = 40). We assessed the efficacy of TROP-2-targeting agents in a mouse xenograft model generated from prostate cancer cell lines.

RESULTS

We demonstrated that TACSTD2 is expressed in mCRPC from luminal and basal tumors but at lower levels in patients with neuroendocrine prostate cancer. Patients previously treated with ARSI showed no significant difference in TACSTD2 expression, whereas patients with detectable AR-V7 expression showed increased expression. We observed that TROP-2 can serve as a cell surface target for isolating CTCs, which may serve as a predictive biomarker for ADCs. We also demonstrated that prostate cancer cell line xenografts can be targeted specifically by labeled anti-TROP-2 agents in vivo.

CONCLUSIONS

These results support further studies on TROP-2 as a therapeutic and diagnostic target for mCRPC.

Replication competent retrovirus testing (RCR) in the National Gene Vector Biorepository: No evidence of RCR in 1,595 post-treatment peripheral blood samples obtained from 60 clinical trials

The clinical impact of any therapy requires the product be safe and effective. Gammaretroviral vectors pose several unique risks, including inadvertent exposure to replication competent retrovirus (RCR) that can arise during vector manufacture. The US FDA has required patient monitoring for RCR, and the National Gene Vector Biorepository is an NIH resource that has assisted eligible investigators in meeting this requirement. To date, we have found no evidence of RCR in 338 pre-treatment and 1,595 post-treatment blood samples from 737 patients associated with 60 clinical trials. Most samples (75%) were obtained within 1 year of treatment, and samples as far out as 9 years after treatment were analyzed. The majority of trials (93%) were cancer immunotherapy, and 90% of the trials used vector products produced with the PG13 packaging cell line. The data presented here provide further evidence that current manufacturing methods generate RCR-free products and support the overall safety profile of retroviral gene therapy.

Gene-based Confirmatory Germline Testing Following Tumor-only Sequencing of Prostate Cancer

BACKGROUND

Tumor-only genomic profiling is an important tool in therapeutic management of men with prostate cancer. Since clinically actionable germline variants may be reflected in tumor profiling, it is critical to identify which variants have a higher risk of being germline in origin to better counsel patients and prioritize genetic testing.

OBJECTIVE

To determine when variants found on tumor-only sequencing of prostate cancers should prompt confirmatory germline testing.

DESIGN, SETTING, AND PARTICIPANTS

Men with prostate cancer who underwent both tumor and germline sequencing at Memorial Sloan Kettering Cancer Center from January 1, 2015 to January 31, 2020 were evaluated.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Tumor and germline profiles were analyzed for pathogenic and likely pathogenic ("pathogenic") variants in 60 moderate- or high-penetrance genes associated with cancer predisposition. The germline probability (germline/germline + somatic) of a variant was calculated for each gene. Clinical and pathologic factors were analyzed as potential modifiers of germline probability.

RESULTS AND LIMITATIONS

Of the 1883 patients identified, 1084 (58%) had a somatic or germline pathogenic variant in one of 60 cancer susceptibility genes, and of them, 240 (22%) had at least one germline variant. Overall, the most frequent variants were in TP53, PTEN, APC, BRCA2, RB1, ATM, and CHEK2. Variants in TP53, PTEN, or RB1 were identified in 746 (40%) patients and were exclusively somatic. Variants with the highest germline probabilities were in PALB2 (69%), MITF (62%), HOXB13 (60%), CHEK2 (55%), BRCA1 (55%), and BRCA2 (47%), and the overall germline probability of a variant in any DNA damage repair gene was 40%. Limitations were that most of the men included in the cohort had metastatic disease, and different thresholds for pathogenicity exist for somatic and germline variants.

CONCLUSIONS

Of patients with pathogenic variants found on prostate tumor sequencing, 22% had clinically actionable germline variants, for which the germline probabilities varied widely by gene. Our results provide an evidenced-based clinical framework to prioritize referral to genetic counseling following tumor-only sequencing.

PATIENT SUMMARY

Patients with advanced prostate cancer are recommended to have germline genetic testing. Genetic sequencing of a patient's prostate tumor may also identify certain gene variants that are inherited. We found that patients who had variants in certain genes, such as ones that function in DNA damage repair, identified in their prostate tumor sequencing, had a high risk for having an inherited cancer syndrome.

Clinical annotations for prostate cancer research: Defining data elements, creating a reproducible analytical pipeline, and assessing data quality

BACKGROUND

Routine clinical data from clinical charts are indispensable for retrospective and prospective observational studies and clinical trials. Their reproducibility is often not assessed. We developed a prostate cancer-specific database for clinical annotations and evaluated data reproducibility.

METHODS

For men with prostate cancer who had clinical-grade paired tumor-normal sequencing at a comprehensive cancer center, we performed team-based retrospective data collection from the electronic medical record using a defined source hierarchy. We developed an open-source R package for data processing. With blinded repeat annotation by a reference medical oncologist, we assessed data completeness, reproducibility of team-based annotations, and impact of measurement error on bias in survival analyses.

RESULTS

Data elements on demographics, diagnosis and staging, disease state at the time of procuring a genomically characterized sample, and clinical outcomes were piloted and then abstracted for 2261 patients (with 2631 samples). Completeness of data elements was generally high. Comparing to the repeat annotation by a medical oncologist blinded to the database (100 patients/samples), reproducibility of annotations was high; T stage, metastasis date, and presence and date of castration resistance had lower reproducibility. Impact of measurement error on estimates for strong prognostic factors was modest.

CONCLUSIONS

With a prostate cancer-specific data dictionary and quality control measures, manual clinical annotations by a multidisciplinary team can be scalable and reproducible. The data dictionary and the R package for reproducible data processing are freely available to increase data quality and efficiency in clinical prostate cancer research.

Raising the level of cancer care: Feasibility and reported benefit of a virtual tumor board

e18595

Background: Multidisciplinary tumor boards (TBs) are a key component of high-quality oncology care. Access is variable, particularly outside the academic setting, and limited access likely disproportionately impacts underserved patient populations and may contribute to healthcare disparities. Virtual tumor boards (VTBs) may provide a solution. Methods: Objectives of this endeavor are to test the feasibility of conducting VTBs and assess their perceived benefit and educational value. Expert US faculty formed VTB panels via an online platform to discuss complex cases submitted by clinicians. Each panel included a moderator and a radiologist, as well as a medical, radiation and surgical oncologist. After the panel discussion, written recommendations and video recordings (de-identified) were shared with submitters. Recordings were available online to viewers with embedded questions to assess learning. Submitters were surveyed as to their perceived benefit of the discussion. Viewers were surveyed to assess the educational value. Results: From 07/2020-12/2021, 323 cases (97 breast, 109 thoracic, 49 gastrointestinal, 37 genitourinary, 31 hematologic) were submitted by 48 clinicians to 38 VTBs. Submitters were surveyed with a 73% response rate; 100% reported they were likely to submit a future case for discussion and that they believe the VTB will improve care for patients. Viewers (n = 39) were surveyed with a 72% response rate and included trainees and APPs working in medical, radiation, and surgical oncology as well as radiology. All viewers endorsed that the videos were a good educational resource, and that they would use them in the future. Both embedded questions were answered 74% of the time (315/425); answers post-viewing changed 43% of the time (137/315). Conclusions: VTBs are feasible and lead to a high degree of satisfaction among case submitters. In this cohort, users reported that their patient management changed based on the discussion. Of those who discussed the case at their own TB, most felt that the VTB expanded upon prior recommendations. A large proportion of users stated that their case was not discussed at an internal TB, suggesting the VTB may address an unmet need. Those who watched the videos found them to be a good resource and would use them in the future. Data from larger cohorts will be key in understanding the full impact of this endeavor, particularly in helping to address healthcare disparities.[Table: see text]

Phase 1 study of P-PSMA-101 CAR-T cells in patients with metastatic castration-resistant prostate cancer (mCRPC)

98

Background: P-PSMA-101 is an autologous CAR-T therapy targeting PSMA, with a high percentage of stem cell memory T cells (TSCM) associated with efficacy, safety, and bone homing (particularly relevant to prostate cancer). It is manufactured using a novel non-viral transposon system (piggyBac) that creates high TSCM products. Genes are inserted encoding a PSMA-targeted Centyrin CAR, iCasp9-based safety switch, and DHFR to purify CAR-T cells. P-PSMA-101 completely eliminated tumors in intractable murine models of prostate cancer, providing rationale for this phase 1 trial (NCT04249947). Methods: Patients with mCRPC treated with or not eligible for a CYP17 inhibitor or second-generation antiandrogen, and a taxane were enrolled. P-PSMA-101 was manufactured from apheresed T cells and administered IV following a standard 3-day cy/flu lymphodepletion regimen. Dose escalation from 0.25-15 x 106 cells/kg is planned. Results: As of September 30, 2021, P-PSMA-101 had been administered to 10 heavily pretreated patients (median 7 prior regimens; range 3-15). Single infusions of 0.25 (n=5) to 0.75 (n=5) x 106 cells/kg have been assessed, with dose escalation continuing. P-PSMA-101 cells were shown to expand in blood via qPCR assay, peaking 2-3 weeks after infusion, consistent with the high percentage of TSCM. Significant antitumor responses were seen in this preliminary data set. Declines in PSA were seen in 7 patients (>50% in 3 and >99% in 1). Of 4 patients who had pre- and post-treatment FDG and PSMA-PET imaging, 3 demonstrated marked to complete resolution of abnormal uptake at known metastatic disease sites, with concordance in bone and CT scans, and/or circulating tumor cells (CTC). In 1 case, post-treatment tumor biopsy demonstrated infiltration by P-PSMA-101 CAR-T cells and elimination of tumor cells (pathologic complete response). Safety was consistent with expectations for a CAR-T product. CRS was seen in 60% (10% Gr ≥3) of patients. DLT was seen in 1 patient with macrophage activation syndrome/uveitis, and was the only Gr ≥3 CRS event. Immune effector cell-associated neurotoxicity syndrome (ICANS) has not occurred. CRS marker elevations were modest (max IL-6: 642.6 pg/mL). The most common AEs were cytopenias, infections, and constitutional symptoms (Gr ≥3 60%, 10%, and 0%), as expected with lymphodepletion. Treatable related ocular AEs were noted in 3 patients. Conclusions: These results parallel preclinical findings that P-PSMA-101 can produce marked efficacy in mCRPC, and very low doses are highly efficacious, consistent with unique product attributes such as the TSCM phenotype and bone tropism. This is the first report demonstrating profound antitumor effects of a novel PSMA-directed CAR-T-cell platform with concordant biochemical, radiographic, and pathologic parameters, demonstrating that therapeutic benefit of unarmored CAR-T cells in a major solid tumor is possible. Clinical trial information: NCT04249947.

Clinical annotations for prostate cancer research: Defining data elements, creating a reproducible analytical pipeline, and assessing data quality

64

Background: Routine clinical data from the electronic medical record are indispensable for retrospective and prospective observational studies and clinical trials. Their reproducibility is often not assessed. We sought to develop a prostate cancer-specific database with a defined source hierarchy for clinical annotations and to evaluate data reproducibility. Methods: At a comprehensive cancer center, we designed and implemented a clinical database for men with prostate cancer and clinical-grade paired tumor–normal sequencing for whom we performed team-based retrospective clinical data annotation from the electronic medical record, using a prostate cancer-specific data dictionary. We developed an open-source R package for data processing. We then evaluated completeness of data elements, reproducibility of team-based annotation using blinded repeat annotation by a medical oncologist as the reference, and the impact of measurement error on bias in survival analyses. Results: Data elements on demographics, diagnosis and staging, disease state at the time of procuring a genomically characterized sample, and clinical outcomes were piloted and then abstracted for 2,261 patients and their 2,631 genomically profiled samples. Completeness of data elements was generally high, between 55% to 99% for elements of clinical TNM staging, self-reported race, biopsy Gleason score, and presence of variant histologies, both for the team-based annotation and the repeat annotation. Comparing team-based annotation to the repeat annotation (100 patients/samples), reproducibility of annotations was high to very high. For 7 binary data elements, both sensitivity and specificity of the team-based annotation reached or exceeded 90%. The T stage, metastasis date, and presence and date of castration resistance had lower reproducibility. Impact of measurement error on estimates for strong prognostic factors was modest. Conclusions: With a prostate cancer-specific data dictionary and quality control measures, manual team-based annotations can be scalable and reproducible. The data dictionary and the R package for reproducible data processing tools provided (https://stopsack.github.io/prostateredcap) are freely available to help increase data quality in clinical prostate cancer research.

Differences in Prostate Cancer Genomes by Self-reported Race: Contributions of Genetic Ancestry, Modifiable Cancer Risk Factors, and Clinical Factors

PURPOSE

Black men die from prostate cancer twice as often as White men, a disparity likely due to inherited genetics, modifiable cancer risk factors, and healthcare access. It is incompletely understood how and why tumor genomes differ by self-reported race and genetic ancestry.

EXPERIMENTAL DESIGN

Among 2,069 men with prostate cancer (1,841 self-reported White, 63 Asian, 165 Black) with access to clinical-grade sequencing at the same cancer center, prevalence of tumor and germline alterations was assessed in cancer driver genes reported to have different alteration prevalence by race.

RESULTS

Clinical characteristics such as prostate-specific antigen and age at diagnosis as well as cancer stage at sample procurement differed by self-reported race. However, most genomic differences persisted when adjusting for clinical characteristics. Tumors from Black men harbored fewer PTEN mutations and more AR alterations than those from White men. Tumors from Asian men had more FOXA1 mutations and more ZFHX3 alterations than White men. Despite fewer TP53 mutations, tumors from Black men had more aneuploidy, particularly chromosome arm 8q gains, an adverse prognostic factor. Genetic ancestry was associated with similar tumor alterations as self-reported race, but also with modifiable cancer risk factors. Community-level average income was associated with chr8q gains after adjusting for race and ancestry.

CONCLUSIONS

Tumor genomics differed by race even after accounting for clinical characteristics. Equalizing access to care may not fully eliminate such differences. Therapies for alterations more common in racial minorities are needed. Tumor genomic differences should not be assumed to be entirely due to germline genetics.

Randomized Phase 2 Trial of Abiraterone Acetate Plus Prednisone, Degarelix, or the Combination in Men with Biochemically Recurrent Prostate Cancer After Radical Prostatectomy

Background

Phase 2 trial endpoints that can be utilized in high-risk biochemical recurrence (BCR) after prostatectomy as a way of more rapidly identifying treatments for phase 3 trials are urgently needed. The efficacy of abiraterone acetate plus prednisone (AAP) in BCR is unknown.

Objective

To compare the rates of complete biochemical responses after testosterone recovery after 8 mo of AAP and degarelix, a gonadotropin-releasing hormone antagonist, alone or in combination.

Design, setting, and participants

Patients with BCR (prostate-specific antigen [PSA] ≥1.0 ng/ml, PSA doubling time ≤9 mo, no metastases on standard imaging, and testosterone ≥150 ng/dl) after prostatectomy (with or without prior radiotherapy) were included in this study.

Intervention

Patients were randomized to AAP (arm 1), AAP with degarelix (arm 2), or degarelix (arm 3) for 8 mo, and monitored for 18 mo.

Outcome measurements and statistical analysis

The primary endpoint was undetectable PSA with testosterone >150 ng/dl at 18 mo. Secondary endpoints were undetectable PSA at 8 mo and time to testosterone recovery.

Results and limitations

For the 122 patients enrolled, no difference was found between treatments for the primary endpoint (arm 1: 5.1% [95% confidence interval {CI}: 1–17%], arm 2: 17.1% [95% CI: 7–32%], arm 3: 11.9% [95% CI: 4–26%]; arm 1 vs 2, p = 0.93; arm 2 vs 3, p = 0.36). AAP therapy showed the shortest median time to testosterone recovery (36.0 wk [95% CI: 35.9–36.1]) relative to degarelix (52.9 wk [95% CI: 49.0–56.0], p < 0.001). Rates of undetectable PSA at 8 mo differed between AAP with degarelix and degarelix alone (p = 0.04), but not between AAP alone and degarelix alone (p = 0.12). Limitations of this study include a lack of long-term follow-up.

Conclusions

Rates of undetectable PSA levels with testosterone recovery were similar between arms, suggesting that increased androgen suppression with AAP and androgen deprivation therapy (ADT) is unlikely to eradicate recurrent disease compared with ADT alone.

Patient summary

We evaluated the use of abiraterone acetate plus prednisone (AAP) and androgen deprivation therapy (ADT), AAP alone, or ADT alone in men with biochemically recurrent, nonmetastatic prostate cancer. While more men who received the combination had an undetectable prostate-specific antigen (PSA) level at 8 mo on treatment, once men came off treatment and testosterone level rose, there was no difference in the rates of undetectable PSA levels. This suggests that the combination is not able to eradicate disease any better than ADT alone.

Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Prostate Cancer: The Primary Results of the PRONOUNCE Randomized Trial

BACKGROUND

The relative cardiovascular safety of gonadotropin-releasing hormone (GnRH) antagonists compared with GnRH agonists in men with prostate cancer and known atherosclerotic cardiovascular disease remains controversial.

METHODS

In this international, multicenter, prospective, randomized, open-label trial, men with prostate cancer and concomitant atherosclerotic cardiovascular disease were randomly assigned 1:1 to receive the GnRH antagonist degarelix or the GnRH agonist leuprolide for 12 months. The primary outcome was the time to first adjudicated major adverse cardiovascular event (composite of death, myocardial infarction, or stroke) through 12 months.

RESULTS

Because of slower-than-projected enrollment and fewer-than-projected primary outcome events, enrollment was stopped before the 900 planned participants were accrued. From May 3, 2016, to April 16, 2020, a total of 545 patients from 113 sites across 12 countries were randomly selected. Baseline characteristics were balanced between study groups. The median age was 73 years, 49.8% had localized prostate cancer; 26.3% had locally advanced disease, and 20.4% had metastatic disease. A major adverse cardiovascular event occurred in 15 (5.5%) patients assigned to degarelix and 11 (4.1%) patients assigned to leuprolide (hazard ratio, 1.28 [95% CI, 0.59-2.79]; P=0.53).

CONCLUSIONS

PRONOUNCE (A Trial Comparing Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Advanced Prostate Cancer and Cardiovascular Disease) is the first, international, randomized clinical trial to prospectively compare the cardiovascular safety of a GnRH antagonist and a GnRH agonist in patients with prostate cancer. The study was terminated prematurely because of the smaller than planned number of participants and events, and no difference in major adverse cardiovascular events at 1 year between patients assigned to degarelix or leuprolide was observed. The relative cardiovascular safety of GnRH antagonists and agonists remains unresolved. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02663908.

TROP-2 co-expression with androgen receptor splice variants as a new therapeutic target in prostate cancer

5060

Background: Tumor-associated calcium signal transducer 2 (TROP-2, TACSTD2) is a transmembrane glycoprotein that is highly expressed in many epithelial cancers. Overexpression of TROP-2 is postulated to mediate cancer cell growth, invasion, and is associated with more aggressive disease. TROP-2 has emerged as a therapeutic target for antibody-drug conjugates in clinical trials including sacituzumab govitecan and DS-1062. Here, we evaluated the expression of TROP-2 in tumor biopsies and circulating tumor cells (CTCs) in men with metastatic castration resistant prostate cancer (mCRPC) to evaluate TROP-2 as a clinically relevant target. Methods: RNA-seq data from the SU2C-PCF database and PROMOTE clinical trial (NCT#01953640) was assessed for TACSTD2 and androgen receptor (AR) splice variant ( AR_V7/AR_V9) expression. Prostate cancer ChIP-seq data was analyzed to identify binding of the AR to the TROP-2 promoter. EpCAM and TROP-2 captured CTCs were isolated from patients with mCRPC using the VERSA (Versatile Exclusion-based Rare Sample Analysis) platform and assessed for splice variant, neuroendocrine (NE), and AR-regulated gene signatures, in addition to CTC enumeration and TROP-2 protein expression. Results: TROP-2 expression was detectable in 90% of patients, in both bone and visceral metastatic biopsies (SUC2-PCF). Although TROP-2 low biopsies were infrequent (10%), 58% of these samples showed high levels of NE markers, as compared with 5% in all other patients. In the PROMOTE study, elevated TROP-2 gene expression was significantly higher in biopsies with high AR_V7 expression than in those with low (p = 0.04) or negative (p <.01) AR_V7 expression. ChIP-seq data demonstrated binding of AR at the TROP-2 promoter as well as at a potential enhancer site upstream, suggesting that TROP-2 expression can be regulated by AR activity. Splice variants and NE gene signatures were expressed in CTCs captured with both EpCAM and TROP-2, although markedly different gene expression profiles between EpCAM and TROP-2 CTCs were observed in a subset of patients with neuroendocrine prostate cancer. Detection of AR_V7 from TROP-2 CTCs corresponded to shorter overall survival in 20 patients with mCRPC. TROP-2 protein expression was identified on EpCAM captured CTCs, although patients exhibited a wide degree of both intra- and inter-patient heterogeneity. Conclusions: Our findings demonstrate that TROP-2 is highly expressed in mCRPC, and is reduced in a subset of patient tumors expressing neuroendocrine markers. In the PROMOTE clinical trial with abiraterone acetate, TROP-2 AR variant expression correlated with increased TROP-2 expression. Binding of the AR to the TROP-2 promoter and potential enhancer was observed in prostate cancer cell lines and biopsies. These results indicate TROP-2 is a high value a biomarker and therapeutic target mCRPC.

Interim results of aasur: A single arm, multi-center phase 2 trial of apalutamide (A) + abiraterone acetate + prednisone (AA+P) + leuprolide with stereotactic ultra-hypofractionated radiation (UHRT) in very high risk (VHR), node negative (N0) prostate cancer (PCa)

5012

Background: Standard of care in VHR PCa is radiation therapy (RT) with 18-36 months (mos) of androgen-deprivation therapy (ADT). With this regimen, chronic ADT toxicity is significant and biochemical recurrence (BCR) frequent. We sought to improve tumor control and minimize toxicity with intensified short course ADT with dual androgen receptor signaling inhibitors (ARSI) and UHRT. Methods: 64 patients (pts) with VHR, N0 PCa were enrolled from 4 centers. VHR PCa was defined as Gleason score (GS) 9-10, >4 cores of GS 8 disease, or 2 high-risk features (including rT3/T4 disease). Treatment (tx) involved 6 mos of A, AA+P, and leuprolide with prostate/seminal vesicle-directed RT (7.5-8 Gy x 5 fractions). The primary endpoint was BCR defined as nadir PSA + 2ng/mL. Biochemical recurrence-free survival (bRFS) is reported herein. Our hypothesized reduction in BCR from 25% to 10% at 3 years (yrs) required 53 pts to provide a power of 0.84 and an alpha of 0.03. Undetectable PSA was defined as <0.10 ng/mL. Non-castrate testosterone (T) was a post-tx value >150 ng/mL. All analyses were intention-to-treat. Toxicity and health-related quality of life measures were evaluated using CTCAEv4.0 and the EPIC-26 questionnaire. Results: Baseline characteristics are summarized in the Table; 63 of 64 pts completed protocol tx. Median time to nadir PSA from tx start was 2 mos (range, 1-9); 63 of 64 pts (98.4%) achieved an undetectable nadir PSA. Median time to post-tx, non-castrate T was 6.5 mos (range, 2.5-25.5). Median follow-up (f/u) for pts without BCR was 30 mos (range, 15-44). Seven pts had BCR; 2-yr bRFS was 95.0% (95% CI, 89.7-100); 3-yr bRFS was 89.7% (95 CI, 81.0-99.3). For the 57 pts without BCR, 56 (98.2%) had T > 150ng/mL at last f/u; median PSA at last f/u was 0.10 ng/mL (IQR, <0.10-0.30); of these, 40 (70.2%) pts had PSAs ≤ 0.20 ng/mL with 24 (42.1%) undetectable. Fifteen pts experienced transient Grade 3 toxicities: 12 (18.8%) with hypertension and 3 with rash (4.7%). EPIC-26 scores for a subset of pts (n=21) at baseline and 12 mos showed no significant decline in urinary or bowel domains; declines in sexual (-11.9) and hormone (-5.7) domains met significance. Conclusions: Compared to historic controls with the long course ADT, AASUR demonstrated impressive 3-yr bRFS, rapid T recovery, and limited toxicities; the safety profile of this regimen was consistent with the known AE profile of the ARSI and RT. This regimen warrants further, randomized evaluation. Funded by Janssen Pharmaceuticals. Managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT02772588. [Table: see text]

RNA Based Approaches to Profile Oncogenic Pathways From Low Quantity Samples to Drive Precision Oncology Strategies

Precision treatment of cancer requires knowledge on active tumor driving signal transduction pathways to select the optimal effective targeted treatment. Currently only a subset of patients derive clinical benefit from mutation based targeted treatment, due to intrinsic and acquired drug resistance mechanisms. Phenotypic assays to identify the tumor driving pathway based on protein analysis are difficult to multiplex on routine pathology samples. In contrast, the transcriptome contains information on signaling pathway activity and can complement genomic analyses. Here we present the validation and clinical application of a new knowledge-based mRNA-based diagnostic assay platform (OncoSignal) for measuring activity of relevant signaling pathways simultaneously and quantitatively with high resolution in tissue samples and circulating tumor cells, specifically with very small specimen quantities. The approach uses mRNA levels of a pathway's direct target genes, selected based on literature for multiple proof points, and used as evidence that a pathway is functionally activated. Using these validated target genes, a Bayesian network model has been built and calibrated on mRNA measurements of samples with known pathway status, which is used next to calculate a pathway activity score on individual test samples. Translation to RT-qPCR assays enables broad clinical diagnostic applications, including small analytes. A large number of cancer samples have been analyzed across a variety of cancer histologies and benchmarked across normal controls. Assays have been used to characterize cell types in the cancer cell microenvironment, including immune cells in which activated and immunotolerant states can be distinguished. Results support the expectation that the assays provide information on cancer driving signaling pathways which is difficult to derive from next generation DNA sequencing analysis. Current clinical oncology applications have been complementary to genomic mutation analysis to improve precision medicine: (1) prediction of response and resistance to various therapies, especially targeted therapy and immunotherapy; (2) assessment and monitoring of therapy efficacy; (3) prediction of invasive cancer cell behavior and prognosis; (4) measurement of circulating tumor cells. Preclinical oncology applications lie in a better understanding of cancer behavior across cancer types, and in development of a pathophysiology-based cancer classification for development of novel therapies and precision medicine.

Immunotherapy for Prostate Cancer: Treatments for the "Lethal" Phenotype

Multiple immunologic platforms have provided minimal impact in patients with metastatic castration-resistant prostate cancer, necessitating that novel approaches continue to be developed. Although checkpoint inhibitors have been largely ineffective, there remain small cohorts of patients who have durable responses but lack the conventional indicators for response to this class of drugs, that is, high mutational burden or significant genomic alterations, as seen in other solid tumors. This article presents an update on the evolution of immunotherapeutics that target a more lethal form of prostate cancer and provides the groundwork for future considerations as to how this field should proceed.

Evolving understanding and categorization of prostate cancer: preventing progression to metastatic castration-resistant prostate cancer: RADAR IV

INTRODUCTION To interpret data and update the traditional categorization of prostate cancer in order to help treating clinicians make more informed decisions. These updates include guidance regarding how to best use next generation imaging (NGI) with the caveat that the new imaging technologies are still a work in progress.

MATERIALS AND METHODS

Literature review.

RESULTS

Critical goals in prostate cancer management include preventing or delaying emergence of distant metastases and progression to castration-resistant disease. Pathways for progression to metastatic castration-resistant prostate cancer (mCRPC) involve transitional states: nonmetastatic castration-resistant prostate cancer (nmCRPC), metastatic hormone-sensitive prostate cancer (mHSPC), and oligometastatic disease. Determination of clinical state depends in part on available imaging modalities. Currently, fluciclovine and gallium-68 (⁶⁸Ga) prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) are the NGI approaches with the most favorable combination of availability, specificity, and sensitivity. PET imaging can be used to help guide treatment selection in most patients. NGI can help determine patients who are candidates for new treatments, most notably (next-generation androgen antagonists, eg, apalutamide, enzalutamide, darolutamide), that can delay progression to advanced disease.

CONCLUSIONS

It is important to achieve a consensus on new and more easily understood terminology to clearly and effectively describe prostate cancer and its progression to health care professionals and patients. It is also important that description of disease states make clear the need to initiate appropriate treatment. This may be particularly important for disease in transition to mCRPC.

Immunomodulatory Activity of a Colony-stimulating Factor-1 Receptor Inhibitor in Patients with Advanced Refractory Breast or Prostate Cancer: A Phase I Study

PURPOSE

Tumor-associated macrophages correlate with increased invasiveness, growth, and immunosuppression. Activation of the colony-stimulating factor-1 receptor (CSF-1R) results in proliferation, differentiation, and migration of monocytes/macrophages. This phase I study evaluated the immunologic and clinical activity, and safety profile of CSF-1R inhibition with the mAb LY3022855.

PATIENTS AND METHODS

Patients with advanced refractory metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (mCRPC) were treated with LY3022855 intravenously in 6-week cycles in cohorts: (A) 1.25 mg/kg every 2 weeks (Q2W); (B) 1.0 mg/kg on weeks 1, 2, 4, and 5; (C) 100 mg once weekly; (D)100 mg Q2W. mCRPC patients were enrolled in cohorts A and B; patients with MBC were enrolled in all cohorts. Efficacy was assessed by RECIST and Prostate Cancer Clinical Trials Working Group 2 criteria.

RESULTS

Thirty-four patients (22 MBC; 12 mCRPC) received ≥1 dose of LY3022855. At day 8, circulating CSF-1 levels increased and proinflammatory monocytes CD14^DIMCD16^BRIGHT decreased. Best RECIST response was stable disease in five patients with MBC (23%; duration, 82-302 days) and three patients with mCRPC (25%; duration, 50-124 days). Two patients with MBC (cohort A) had durable stable disease >9 months and a third patient with MBC had palpable reduction in a nontarget neck mass. Immune-related gene activation in tumor biopsies posttreatment was observed. Common any grade treatment-related adverse events were fatigue, decreased appetite, nausea, asymptomatic increased lipase, and creatine phosphokinase.

CONCLUSIONS

LY3022855 was well tolerated and showed evidence of immune modulation. Clinically meaningful stable disease >9 months was observed in two patients with MBC.

Changes in ki-67 and cleaved caspase-3 (CC3) with short term androgen deprivation therapy (ADT) prior to prostatectomy as part of a trial in intermediate and high-risk prostate cancer (PC)

e17502

Background: Ki-67 and CC3 are markers of cellular proliferation and apoptosis and have been associated with prognosis in localized PC. Testosterone suppression promotes a time-dependent modulation of these indices. We explored changes in Ki-67 and CC3 at different timepoints in a pilot trial using short-term ADT prior to radical prostatectomy (RP). Methods: Pts with intermediate and high-risk localized PC were randomized to receive a single dose of neoadjuvant degarelix (240 mg SC) either 4 ± 1 days (Cohort A) or 7 ± 1 days (Cohort B) prior to RP. Anatomically matched tumor foci from the pre-treatment diagnostic biopsy and the prostatectomy specimens were assessed by immunohistochemistry (IHC) for Ki-67, CC3, and PTEN expression. Results: 32 pts were randomized: 15 to Cohort A and 17 to Cohort B. Ki-67 and CC3 expression in the pre- and post-treatment samples for both cohorts are summarized in the table. A significant reduction in Ki-67 and increase in CC3 expression occurred in both cohorts (all p-values < 0.05). No difference was found when the absolute difference of Ki-67 expression was compared between Cohort A and Cohort B (p = 0.7). A significant reduction of Ki-67 and increase in CC3 expression occurred in pts independent of PTEN status. Conclusions: A reduction of Ki-67 and an increase in CC3 expression was achieved in both cohorts following a single dose of degarelix within 1 week of RP. Although loss of PTEN has been associated with androgen-independent progression, reduction of proliferation and increase in apoptosis levels were achieved independent of PTEN status in this small cohort. Further analyses are ongoing to correlate the pathologic findings with clinical outcomes. Clinical trial information: NCT01542021 . [Table: see text]

Evaluation of immune-related adverse events (irAE): Utilizing the patient-reported outcomes of the common terminology criteria for adverse events (PRO-CTCAE) in a phase II study of ipilimumab (ipi) in men with castration-sensitive prostate cancer (CSPC)

e24174

Background: Incorporation of the PRO-CTCAE during chemotherapy is associated with fewer ER visits and improved survival. Limited data exist using this tool to capture irAE in immunotherapy trials. We collected select PRO-CTCAEs in a clinical trial evaluating an immune checkpoint inhibitor (ICI) in patients (pts) with CSPC. Methods: Cohort A (Coh A) enrolled de novo metastatic CSPC; Cohort B (Coh B) enrolled recurrent CSPC after radical prostatectomy (RP). Treatment consisted of 4 doses of ipi and 8 months of androgen deprivation therapy (ADT) in Coh A & B, and RP in Coh A. PRO-CTCAEs were collected at each ipi or ADT administration, and during follow-up. PRO-CTCAE items included abdominal pain, diarrhea, fatigue, anorexia, nausea, vomiting, rash and pruritus, with the correspondent attributes of frequency (freq), severity (sev), interference (int), and presence. Results: 16 pts were treated (Coh A: 7; Coh B: 9) with 181 matched pairs of PRO-CTCAE and CTCAE. The study was terminated early for an unfavorable risk:benefit ratio. PRO-CTCAE completion at required visits was 85.4% in Coh A and 98.1% in Coh B. Cohen’s kappa coefficients was lowest for pruritus (k = 0.10, slight agreement) and highest for rash (k = 0.64, moderate agreement). CTCAE captured diarrhea in 10 pts, 4 of whom received steroids. 75% (3/4) of pts receiving steroids graded diarrhea as ‘frequently’ or ‘almost constantly’ on the PRO-CTCAE while 66.7% (4/6) of those who did not receive steroids reported the same frequency. Conclusions: IrAE were more commonly reported and of higher grade by patients using the PRO-CTCAE as compared to clinician reporting, consistent with existing literature in non-ICI studies. Diarrhea as reported by the PRO-CTCAE did not associate with steroid use in this small trial. Further studies are needed to evaluate irAE using PRO-CTCAEs and the potential role in management of these toxicities. Clinical trial information: NCT02020070 . [Table: see text]

Immunotherapy for castration-resistant prostate cancer: has its time arrived?

Introduction: Within the last decade, multiple innovative immune platforms have been developed and tested in patients with metastatic castration-resistant prostate cancer (mCRPC) with only one demonstrating a survival benefit. The advent of immunogenomics along with the availability of diverse checkpoint inhibitors provides inroads in treating these patients, in many cases with significant clinical impact but unfortunately not in all patients. How to exploit these novel platforms remains an area of increased interest especially in the setting of new agents that can affect the tumor microenvironment and potentially render a 'cold' tumor to become 'hot.'Areas covered: This review highlights the current changes and challenges in this field and how to best use our current knowledge for better trial designs in patients with mCRPC.Expert opinion: Recent understanding of the inhibitory milieu within the tumor microenvironment has fostered the use of combinatorial strategies that target not only tumor cells but capitalize on controlling inhibitory cell populations and cytokines that induce a hostile setting for immune cells. Immunogenomics and genomic interrogation of prostate cancers have opened a vista as to how patients' tumors that can respond to immune agents that previously were thought have minimal antitumor activity.

Cardiovascular Safety of Degarelix Versus Leuprolide for Advanced Prostate Cancer: The PRONOUNCE Trial Study Design

OBJECTIVES

This study will compare the incidence of major adverse cardiovascular events (MACEs) with androgen deprivation therapy (ADT) among men with advanced prostate cancer who are being treated with a gonadotropin-releasing hormone (GnRH) antagonist versus a GnRH agonist.

BACKGROUND

Treatment of advanced prostate cancer with ADT might increase the risk of subsequent cardiovascular events among men with known atherosclerotic cardiovascular disease (ASCVD), but a recent meta-analysis suggested that this risk might be lower with ADT using a GnRH antagonist versus a GnRH agonist.

METHODS

PRONOUNCE is a multicenter, prospective, randomized, open, blinded endpoint trial that will enroll approximately 900 patients with advanced prostate cancer and pre-existing ASCVD who will be treated with ADT. Participants will be randomized to receive the GnRH antagonist degarelix or the GnRH agonist leuprolide as ADT for 12 months. The primary endpoint is time from randomization to first confirmed, adjudicated occurrence of a MACE, which is defined as a composite of all-cause death, nonfatal myocardial infarction, or nonfatal stroke through 12 months of ADT treatment. Baseline cardiovascular biomarkers (high-sensitivity C-reactive protein, high-sensitivity troponin T, and N-terminal pro-brain natriuretic peptide), as well as serial inflammatory and immune biomarkers, will be evaluated in exploratory analyses.

RESULTS

As of October 1, 2019, a total of 364 patients have been enrolled. The mean age is 74 years, 90% are white, 80% have hypertension or dyslipidemia, 30% diabetes mellitus, 40% have had a previous myocardial infarction, and 65% have had previous revascularization. Regarding prostate cancer features at randomization, 48% of the patients had localized disease, 23% had locally advanced disease, and 18% had metastatic disease.

CONCLUSIONS

PRONOUNCE is the first prospective cardiovascular outcomes trial in advanced prostate cancer that will delineate whether the risk of subsequent cardiovascular events associated with ADT is lower with a GnRH antagonist versus a GnRH agonist for men with pre-existing ASCVD. (A Trial Comparing Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Advanced Prostate Cancer and Cardiovascular Disease [PRONOUNCE]; NCT02663908).

Analysis of the Prevalence of Microsatellite Instability in Prostate Cancer and Response to Immune Checkpoint Blockade

Importance

The anti-programmed cell death protein 1 (PD-1) antibody pembrolizumab is approved by the US Food and Drug Administration for the treatment of microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) solid tumors, but the prevalence of MSI-H/dMMR prostate cancer and the clinical utility of immune checkpoint blockade in this disease subset are unknown.

Objective

To define the prevalence of MSI-H/dMMR prostate cancer and the clinical benefit of anti-PD-1/programmed cell death 1 ligand 1 (PD-L1) therapy in this molecularly defined population.

Design, Setting, and Participants

In this case series, 1551 tumors from 1346 patients with prostate cancer undergoing treatment at Memorial Sloan Kettering Cancer Center were prospectively analyzed using a targeted sequencing assay from January 1, 2015, through January 31, 2018. Patients had a diagnosis of prostate cancer and consented to tumor molecular profiling when a tumor biopsy was planned or archival tissue was available. For each patient, clinical outcomes were reported, with follow-up until May 31, 2018.

Main Outcomes and Measures

Tumor mutation burden and MSIsensor score, a quantitative measure of MSI, were calculated. Mutational signature analysis and immunohistochemistry for MMR protein expression were performed in select cases.

Results

Among the 1033 patients who had adequate tumor quality for MSIsensor analysis (mean [SD] age, 65.6 [9.3] years), 32 (3.1%) had MSI-H/dMMR prostate cancer. Twenty-three of 1033 patients (2.2%) had tumors with high MSIsensor scores, and an additional 9 had indeterminate scores with evidence of dMMR. Seven of the 32 MSI-H/dMMR patients (21.9%) had a pathogenic germline mutation in a Lynch syndrome-associated gene. Six patients had more than 1 tumor analyzed, 2 of whom displayed an acquired MSI-H phenotype later in their disease course. Eleven patients with MSI-H/dMMR castration-resistant prostate cancer received anti-PD-1/PD-L1 therapy. Six of these (54.5%) had a greater than 50% decline in prostate-specific antigen levels, 4 of whom had radiographic responses. As of May 2018, 5 of the 6 responders (5 of 11 total [45.5%]) were still on therapy for as long as 89 weeks.

Conclusions and Relevance

The MSI-H/dMMR molecular phenotype is uncommon yet therapeutically meaningful in prostate cancer and can be somatically acquired during disease evolution. Given the potential for durable responses to anti-PD-1/PD-L1 therapy, these findings support the use of prospective tumor sequencing to screen all patients with advanced prostate cancer for MSI-H/dMMR. Because not all patients with the MSI-H/dMMR phenotype respond, further studies should explore mechanisms of resistance.

Abiraterone acetate (AA) with or without cabazitaxel (CBZ) in treatment of chemotherapy naive metastatic castration-resistant prostate cancer (mCRPC)

84

Background: Loss of retinoblastoma tumor suppressor (RB) function has been shown to lead to CRPC and is strongly associated with poor outcome. RB functions as a transcriptional repressor; as such, loss of RB causes de-repression of pro-tumorigenic gene networks, including deregulation of the androgen receptor (AR) locus, excessive AR production, and castration-resistant (ligand independent) AR activity that can bypass hormone therapy. Our hypothesis is that leveraging RB status can direct treatment decisions. The primary objective of the trial (NCT02218606) was to determine the radiographic progression free survival (rPFS) of AA/prednisone (AAP) with and without CBZ in mCRPC patients (pts) that have progressed on primary androgen deprivation therapy and no prior AR directed therapy or chemotherapy. Methods: This is a multicenter non-comparative randomized phase 2 trial. Pts were randomized 1:1 to AAP with crossover to CBZ upon AAP failure (Arm 1), or the combination of AAP + CBZ (Arm 2). Randomization was stratified by the CALGB 90401 prognostic risk groups. The primary endpoint was rPFS (time from randomization to radiographic progression or death, whichever occurs first). Arms were analyzed separately. Results: Between October 2014 and March 2019, 93 pts were accrued; 81 were randomized. Median age was 68 years and ECOG performance status was 0 or 1. Endpoints are shown in Table. Therapies were well tolerated. Conclusions: Results of AAP + CBZ (Arm 2) in chemotherapy naïve pts suggest that men may derive benefit from the earlier use of CBZ with acceptable toxicity, supporting further study of this combination in mCRPC pts. Circulating Tumor Cells are being analyzed for changes in RB/AR expression. Managed by: Prostate Cancer Clinical Trials Consortium; Funding: Sanofi US; Support: Prostate Cancer Foundation. Clinical trial information: NCT02218606. [Table: see text]

Single-arm, phase II study to evaluate the safety and efficacy of sacituzumab govitecan in patients with metastatic castration-resistant prostate cancer who have progressed on second generation AR-directed therapy

TPS251

Background: In patients with mCRPC, androgen receptor (AR) pathway inhibitors such as enzalutamide or abiraterone acetate are often used as first-line systemic therapy. After progression on either of these inhibitors, the likelihood of response to the other is significantly lower than in the first-line setting. Multiple resistance mechanisms have been identified, including the emergence of AR splice variants. Trop2 is a cell-surface antigen that is expressed in > 70% of prostate cancers and is enriched in mCRPC expressing AR splice variants. Sacituzumab govitecan (SG; IMMU-132) is a novel antibody drug conjugate composed of humanized anti-Trop2 antibody conjugated to SN-38 payload by hydrolyzable linker. SG has potential to be an effective therapy after progression on initial AR pathway inhibitors to meet this significant unmet clinical need. Methods: This is a single-arm, open-label, multicenter phase 2 trial (NCT03725761) to determine the efficacy and safety of SG. The primary endpoint is PSA response rate (≥50% PSA decline at or within 9 weeks of starting treatment); secondary endpoints include rPFS and overall survival. 55 subjects with mCRPC who have progressed on second-generation AR-directed therapy in either the hormone sensitive or CRPC setting will be included. Fresh or archived metastatic site biopsy is required. Subjects will be treated with SG IV at 10 mg/kg on Day 1 and Day 8 of 21-day cycles until disease progression. Subjects who receive ≥1 SG dose and have ≥1 PSA post-dose assessment will be included in final efficacy analysis. Circulating tumor cell biomarker studies will be performed throughout treatment and at progression to investigate potential mechanisms of response/resistance to SG. Tumor biopsies at baseline and after 3 therapy cycles will evaluate genomic alterations that predict treatment response. Subjects who remain progression free will undergo repeated evaluations of extent of disease every 9 weeks. The trial is actively accruing. Managed by: Prostate Cancer Clinical Trials Consortium; Funding: Immunomedics; Support: Prostate Cancer Foundation. Clinical trial information: NCT03725761.

A Phase I Trial of IGF-1R Inhibitor Cixutumumab and mTOR Inhibitor Temsirolimus in Metastatic Castration-resistant Prostate Cancer

BACKGROUND

Despite frequent PTEN (phosphatase and tensin homologue) loss and Akt/mammalian target of rapamycin (mTOR) signaling in prostate cancer, the disease is insensitive to single-agent mTOR inhibition. Insulin-like growth factor-1 receptor inhibition might mitigate the feedback inhibition by Torc1 inhibitors, suppressing downstream Akt activation and, thus, potentiating the antitumor activity of mTOR inhibition.

PATIENTS AND METHODS

In the present phase I study, patients with metastatic castration-resistant prostate cancer received 6 mg/kg cixutumumab and 25 mg temsirolimus intravenously each week. The primary objective was safety and tolerability. Temsirolimus was decreased if ≥ 2 dose-limiting toxicities (DLTs) were observed in 6 patients. The correlative analyses included measurement of circulating tumor cells, [18F]-fluoro-2-deoxyglucose positron emission tomography, 16β-[18F]-fluoro-α-dihydrotestosterone positron emission tomography, and tumor biopsy.

RESULTS

A total of 16 patients were enrolled across 3 cohorts (1, -1, -2). Two DLTs (grade 3 oral mucositis) were observed in cohort 1 (temsirolimus, 25 mg), and 1 DLT (grade 3 lipase) in cohort -1 (temsirolimus, 20 mg). The most common adverse events included hyperglycemia (100%; 31% grade 3), oral mucositis (63%; 19% grade 3), and diarrhea (44%; 0 grade 3). Low-grade pneumonitis occurred in 7 of 11 patients (44%; 0 grade 3), prompting the opening of a 3-weekly cohort (temsirolimus, 20 mg/kg), without pneumonitis events. No patient had a >50% decline in prostate-specific antigen from baseline. The best radiographic response was stable disease, with median study duration of 22 weeks (range, 7-63 weeks).

CONCLUSIONS

Despite a strong scientific rationale for the combination, temsirolimus plus cixutumumab demonstrated limited antitumor activity and a greater than expected incidence of toxicity, including low-grade pneumonitis and hyperglycemia. Hence, the trial was stopped in favor of alternative androgen receptor/phosphatidylinositol 3-kinase-directed combinatorial therapies.

Evaluation of the patient-reported outcomes common terminology criteria for adverse events (PRO-CTCAE) with abiraterone acetate plus prednisone (AAP), degarelix (D), or the combination in men with biochemically recurrent prostate cancer (BCRPC)

5080

Background: Patient-reported symptoms using the PRO-CTCAE provide insights into the patient experience with care. Earlier use of AAP (an androgen biosynthesis inhibitor plus prednisone) with androgen deprivation therapy in castration sensitive disease may lead to increased symptoms. We previously reported a randomized phase 2 trial of intermittent AAP, D, or AAP+D in BCRPC (NCT01751451) and now share the PRO-CTCAE results. Methods: Men were randomized 1:1:1 to AAP, D, or AAP+D for 8 months, then entered follow up with PSA, testosterone, and safety monitoring. PRO-CTCAE was elicited from patients monthly for hot flashes (HF), fatigue, arthralgias, myalgias, anxiety, depression, sexual function, plus overall QOL. Changes from baseline to end of treatment were compared between groups. AUCs were calculated for each item as a measure of symptom severity over time. Results: 110 men were included. Compliance with PRO-CTCAE reporting from baseline to EOT was 93%. HF did not differ between AAP+D and D, but were increased relative to AAP (all p < 0.05). These differences were consistent when HF were measured as an AUC (all p < 0.01). Fatigue severity did not differ between groups however men receiving AAP reported a small worsening in activity interference from fatigue as compared to AAP+D (p < 0.05). Overall QOL scores were high and did not differ with AAP+D relative to AAP or D. Conclusions: Collection of PRO-CTCAE was feasible and did not demonstrate differences in fatigue, HF, or QOL between AAP+D and D. Comparisons of PRO-CTCAE to matched clinician-reported AEs, and changes in PRO-CTCAE with testosterone recovery during follow up are planned. Clinical trial information: NCT01751451.

Phase 1 study of LY3022855, a colony-stimulating factor-1 receptor (CSF-1R) inhibitor, in patients with metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (MCRPC)

2548

Background: Tumor-associated macrophages (TAM) correlate with increased invasiveness, growth, and immunosuppression. Activation of CSF-1R results in proliferation, differentiation, and migration of monocytes/macrophages. CSF-1R inhibition with LY3022855 (LY), a human immunoglobulin G subclass 1 (IgG1) monoclonal antibody (mAB), may have favorable anti-tumor effects. We evaluated the safety and clinical response of LY monotherapy. Methods: Patients (pts) with advanced refractory MBC and MCRPC received LY intravenously in 6-week cycles in cohorts: A) 1.25 mg/kg every 2 weeks [Q2W]; B) 1.0 mg/kg on Weeks 1, 2, 4, and 5; C) 100 mg once weekly; D)100 mg Q2W. MCRPC pts were enrolled in cohorts A and B; MBC pts were enrolled in all cohorts. Anti-tumor activity was assessed using RECIST v1.1 by radiological imaging every 6 weeks. Results: Thirty-four pts (22 MBC; 12 MCRPC) received ≥1 dose of LY. Median age was 57.0 years (range: 32.0–81.0) for MBC pts and 72.5 years (range: 58.0–84.0) for MCRPC pts. Baseline Eastern Cooperative Oncology Group performance status was 0 (n = 13, 38.2%), 1 (n = 18, 52.9%), or 2 (n = 3, 8.8%). MBC pts were hormone receptor (HR) positive (n = 20), HR negative (n = 1), or unknown (n = 1); 3 MBC pts received concurrent hormone therapy. Common treatment-related adverse events of any grade were fatigue (38.2%), decreased appetite (26.5%), nausea (26.5%), increased lipase (23.5%), and increased creatine phosphokinase (20.6%). No complete or partial response was observed. Stable disease (SD) was observed in 5/22 MBC pts (duration 82–302 days) and 3/7 evaluable MCPRC pts (duration 50–124 days). Two MBC pts (9%; Cohort A) had durable SD > 9 months and 1 pt had palpable reduction in a nontarget neck mass. Circulating CSF1 and IL-34 increased at Day 8 suggestive of target engagement. Pharmacokinetics of LY were consistent with other IgG1 mAbs. Conclusions: LY3022855 was well tolerated and showed evidence of target engagement. Clinically meaningful SD > 9 months was observed in 2 MBC pts. Tumor biomarker analyses are underway. Clinical trial information: NCT02265536.

Baseline genomic and circulating tumor cell (CTC) correlative data from very high-risk (VHR), localized, node-negative prostate cancer patients

e16563

Background: Few data exist on CTC frequency and number, genetic landscape, and tumor mutational burden (TMB) in VHR, node negative, localized prostate cancer (PCa). Methods: We are conducting a single-arm phase 2 trial of ultra-hypofractionated radiation (RT) with 6 months of abiraterone, apalutamide and leuprolide in VHR PCa, defined as: Gleason (Gl) 9-10 or 2 high risk features (including radiographic (r) T3/T4 disease) or > 4 cores of Gl8. We report baseline correlatives in the first 38 screened patients (pts). CTCs were isolated using a non-selection based platform (EPIC Sciences). Additional analyses were conducted using MSK IMPACT, a next generation sequencing assay. Results: Median PSA was 14.8 ng/mL (IQR, 7.7-28.1); Gl7 was present in 5% (n = 2), Gl8 in 32% (n = 12), Gl9 in 61% (n = 23) and Gl10 in 2% (n = 1) of pts; on MR, 42% of pts were rT2 (n = 16), 39% had rT3a disease (n = 15) and 18% had rT3b disease (n = 7). CTC data were available on 31 pts; 74% (n = 23) had ≥1 detectable CTC (range, 0.8-14.6 cells per mL); 29% (n = 9) had CK+ clusters (range, 0.8-7.1 clusters per mL). IMPACT was available for 20 pts: KMT2D/C mutations were present in 25% (n = 4), TP53 missense mutations in 20% (n = 4), FOXA1 mutations in 20% (n = 4), PTEN truncating or missense mutations in 15% (n = 3), SPOP missense mutations in 15% (n = 3), PIK3CA activating mutations in 15% (n = 3), APC deletions in 15% (n = 3); 85% (17/20) had alterations in one of these genes. No clinically significant germline mutations were present. Median TMB was 2.63 mutations/mB (range, 0.87-60.56); the TMB-highest pt had an in-frame deletion in MSH2. Among IMPACTed pts with normalized testosterone post-protocol treatment (n = 16), there was a trend towards an association with SPOP/FOXA1 mutations and undetectable ( < 0.05 ng/mL) PSA; 5/6 pts with mutations had undetectable PSA (83.3%) vs 3/10 without (30%) (p = 0.12). The trial is managed by the PCCTC and funded by Janssen. Conclusions: The genetic profile and TMB of VHR, localized PCa resembles non-castrate, metastatic disease. The frequency of detectable CTCs is high with implications for post-treatment surveillance. SPOP/FOXA1 mutations may predict initial response to RT with total androgen blockade. Clinical trial information: NCT02772588.

Platinum-based chemotherapy in metastatic prostate cancer with alterations in DNA damage repair genes

5038

Background: Platinum-based chemotherapy has shown palliative and radiographic benefit in small unselected studies of metastatic castration-resistant prostate cancer (mCRPC). Alterations in DNA damage repair genes (DDRmut), which occur in ~25% of patients with mCRPC, may sensitize to platinum-based chemotherapy, and may aid in the selection of patients for this therapy. We sought to evaluate the efficacy of platinum-based chemotherapy in DDRmut mCRPC. Methods: We performed a retrospective review of patients with prostate cancer who underwent tumor genomic profiling and received platinum-based chemotherapy. Deleterious alterations in a panel including BRCA2, BRCA1, ATM, FANCA, CDK12 or PALB2 were classified as DDRmut. Absence of deleterious alterations in those genes was classified as DDRwt. MSI-H cases were excluded from analysis. Electronic charts, PSA values, and scans were reviewed to assess for outcomes. Results: From October 2013 to July 2018, 109 patients with mCRPC received platinum-based chemotherapy. 64/109 had prior taxane progression and were PARP inhibitor (PARPi) naïve at the time of platinum-based chemotherapy. DDRmut was found in 16/64 (25%) of patients ( BRCA2, n = 6; ATM, n = 2; CDK12, n = 4; FANCA, n = 4; PALB2, n = 1). Visceral metastasis occurred in 4/16 (25%) of DDRmut patients and in 22/48 (46%) of DDRwt patients. PSA50 responses were more common among DDRmut (8/15 evaluable = 53%, 95% CI, 30-75%) than among DDRwt patients (5/42 evaluable = 12%, 95% CI, 5-25%). Time on platinum-based chemotherapy tended to be longer in the DDRmut group (median 3.1 vs 1.8 months; HR 0.73, 95% CI 0.42-1.26). Of 8 DDRmut patients ( BRCA2, n = 6; BRCA1, n = 1; ATM, n = 2) who received platinum-based chemotherapy after progression on a PARPi, 3/7 evaluable patients (43%) had RECIST response or stable disease, and 2/7 evaluable patients (29%) had a PSA50 response. Of 4 patients with ATM deleterious mutations, none had a radiographic or PSA50 response to platinum-based chemotherapy. Conclusions: Platinum-based chemotherapy showed activity in DDRmut mCRPC patients before and after PARPi treatment.

Tumor testing in men with prostate cancer to predict for germline DNA-damage repair mutations

229

Background: Current guidelines recommend genetic testing for patients (pts) who have BRCA1/2 mutations on tumor-only testing, where germline is not subtracted. The clinical utility of this approach, and possible inclusion of other DDR genes associated with cancer susceptibility, has not been examined in men with prostate cancer. Methods: Pts with mostly advanced prostate cancer were prospectively enrolled to a matched tumor-germline DNA sequencing protocol and consented for disclosure of germline results. Germline analysis was done with an institutional, CLIA-certified next generation sequencing (NGS) platform (MSK-IMPACT) and analyzed for likely pathogenic or pathogenic germline mutations in at least 76 cancer susceptibility genes. Clinical data was retrieved from the medical record. We report on the frequencies in the germline and in the tumor of a subset of DDR genes. Results: 1243 men had analysis of both germline and tumor. Median age 64 (range 35-90). 12% had a second malignancy and 40% reported a relative with prostate cancer. 19% were of Ashkenazi Jewish (AJ) descent. 330 (27%) had any mutation in BRCA1/2, ATM, CHEK2, PALB2, RAD51C, RAD51D, MSH2, MSH6, MLH1, PMS2. 127 (10%) had a germline mutation, of which 36% were AJ founder mutations. For each gene, the percentage of mutations found in germline and tumor is shown in the table. Conclusions: Of prostate cancer pts found to have any DDR mutation on tumor-germline testing, 29% had a germline mutation. Proportion of germline mutations was highest for PALB2, CHEK2 and BRCA2. These findings not only support germline testing when BRCA1/2 mutations are found tumor-only sequencing, but also support germline testing when other DDR mutations are seen. Clinical trial information: NCT01775072. [Table: see text]

Clinicopathologic and genomic characterization of parenchymal brain metastases (BM) in prostate cancer (PCa)

227

Background: BM are rarely seen with PCa, but the incidence may be increasing with contemporary therapies. We sought to evaluate the clinical phenotypes associated with BM and their outcomes. Methods: The MSKCC institutional clinical database from 01/2001 through 06/2018 was reviewed to identify pts with PCa and (1) secondary malignant neoplasm of the brain / spinal cord per ICD-9 (198.3), (2) radiation treatment plan targeting the brain, (3) craniotomy, or (3) notes containing the terms “brain metastasis”. Medical charts were reviewed to confirm diagnosis (dx) and extract data. The logrank statistic and the Cox proportional hazards model were used to determine correlations with overall survival (OS). Results: Of 575 pts who met search criteria, 43 had BM and prostate adenocarcinoma. At PCa dx, median age was 60 years (range: 44 –77 years) and 51% had metastasis (mets). Median time from PCa dx to BM was 4.2 years. At the time of BM dx, 36 had metastatic castration-resistant PCa (mCRPC), 55% had liver mets and 66% had lung mets. 45% had ≥3 lines of therapy for mCRPC prior to BM dx (abiraterone/enzalutamide: 47%, chemotherapy: 91%). The median OS from BM dx was 5.8 months (Table). 4/10 pts with sequencing data had germline mutations ( ATM, BRCA1, BRIP1, MUTYH). To date, 4 BM were sequenced, and 3 showed PTEN loss. Conclusions: BM associated with a poor prognosis and occurred after prolonged treatment. Presence of liver/lung mets, 3 or more BM, and surgical resection (SR) prognosticate for OS in univariate analysis; SR in multivariate analysis. Further analysis is needed to determine if germline mutations and/or PTEN loss associate with BM. [Table: see text]

A phase 2 trial of abiraterone acetate without glucocorticoids for men with metastatic castration-resistant prostate cancer

BACKGROUND

Abiraterone acetate suppresses adrenal androgens and glucocorticoids through the inhibition of CYP17; however, given the risk of mineralocorticoid excess, it is administered with glucocorticoids. Herein, the authors performed a phase 2, single-arm study that was designed to assess the safety of abiraterone acetate without steroids in patients with castration-resistant prostate cancer.

METHODS

Eligible patients had castration-resistant prostate cancer with controlled blood pressure and normal potassium. Patients initially received abiraterone acetate at a dose of 1000 mg daily alone. Those with persistent or severe mineralocorticoid toxicity received treatment with prednisone initiated at a dose of 5 mg twice daily. Therapy was continued until radiographic progression, toxicity, or withdrawal. The primary objective of the current study was to determine the percentage of men requiring prednisone to manage mineralocorticoid toxicity. Toxicity was graded according to Common Terminology Criteria for Adverse Events, version 4.0.

RESULTS

A total of 58 patients received at least 1 dose of abiraterone acetate; the majority had metastases (53 patients; 91.4%). Sixteen patients (27.6%) received prior chemotherapy, 6 patients (10.3%) received prior enzalutamide, and 4 patients (7%) received prior ketoconazole. Grade 3 to 4 adverse events of interest included hypertension (9 patients; 15.5%) and hypokalemia (4 patients; 7%). There was no grade ≥3 edema. Seven patients (12%) initiated prednisone therapy for mineralocorticoid toxicity, 3 patients for hypertension (5%), and 4 patients for hypokalemia (7%). Two patients initiated prednisone therapy for fatigue (3%). Forty patients (68%) experienced a decline in prostate-specific antigen of ≥50% with the use of abiraterone acetate alone. Patients with lower baseline levels of androstenedione (P = .04), androsterone (P = .01), dehydroepiandrosterone (P = .03), and 17-hydroxyprogesterone (P = .03) were found to be more likely to develop mineralocorticoid toxicity.

CONCLUSIONS

Treatment with abiraterone acetate without steroids is feasible, although clinically significant adverse events can occur in a minority of patients. The use of abiraterone acetate without prednisone should be balanced with the potential for toxicity and requires close monitoring.

Immunotherapy for prostate cancer: is prostate an immune responsive tumor?

PURPOSE OF REVIEW

The purpose of this review is to identify possible reasons why prostate cancer suboptimally responds to immune therapies.

RECENT FINDINGS

Interrogation of the intraprostatic milieu suggests that within the normal prostate, foci of tumor can be surrounded by inflammatory cells that may or may not represent foci of immune sensitivity. Whether or not these cells are specific 'immune responders' depends on a multiplicity of factors within the host and intratumoral/stromal milieu. Solid tumors such as kidney and melanoma can undergo spontaneous regressions alone or upon removal of a primary mass lesion, suggestive of some sort of immune derepression once the original lesion is removed. Such observations, though rare, suggest that some unknown immunologic process may be governing how the tumor behaves. Similarly, in melanoma, there are rare abscopal effects suggesting that once a primary lesion is radiated, a secondary lesion afar from the treated lesion could remit.

SUMMARY

Why prostate cancer remains an immunologic conundrum remains a mystery. Patients with metastatic prostate cancer have a survival benefit but minimal or no antitumor response with the autologous cellular product immune therapy, sipuleucel-T, whereas checkpoint inhibitors, successful in melanoma, renal cell, nonsmall cell lung, and urothelial cancers, have little or no activity. This review serves to bring to the forefront the issues that may underlie why prostate cancer is not robustly responsive to immune strategies.

Immunotherapy for biochemically recurrent prostate cancer

215

Background: Annually about 30-50,000 men are diagnosed with biochemically recurrent prostate cancer (BCRpc), defined by a rising PSA after radical prostatectomy (RP) or definitive radiation therapy (RT) with negative conventional imaging (CT and bone scan). Standard treatments include salvage therapies, androgen deprivation or surveillance. The role of immunotherapy in BCRpc is undefined. Methods: This study evaluates PROSTVAC, a pox-viral based therapeutic cancer vaccine targeting PSA, in BCRpc. Key eligibility criteria include PSA > 0.8 after RP or > 2.0 after RT with a maximum PSA of 30, PSA doubling time (DT): 5-15 months; testosterone > 100, negative CT and bone scan. Patients (pts) are randomized to vaccine for 6 months or 6 months surveillance followed by 6 months of vaccine. In a post hoc analysis delayed PSA declines were characterized as a confirmed PSA decline after an intra-study apex PSA (ISAP) defined by a peak PSA affirmed by a contiguous PSA within 10% (to exclude lab variations). 80 pts will be enrolled at NCI, Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center. Results: Of the 26 pts enrolled thus far, 22 have been followed for > 9 months after vaccine and are evaluable. On-study median values were age 66.8 years (54-78), PSA 2.67 ng/ml (0.83-28.5), PSA DT 7.5 months (5.1-14.9). 8 pts (38%) had delayed PSA declines after ISAP (-12% to -99%). Of 13 pts on surveillance for 6 months, only one pt had a similar decline lasting only 56 days. Conclusions: Preliminary data from this study suggests that PROSTVAC may be associated with delayed, but sustained PSA declines in BCRpc which are rarely seen in surveillance alone. Additional data will be acquired from this study, but this provides rationale to develop immunotherapy combinations in BCRpc. Clinical trial information: NCT02649439. [Table: see text]

A multicenter, randomized, controlled trial comparing the occurrence of major adverse cardiovascular events (MACEs) in patients (pts) with prostate cancer (pc) and cardiovascular disease (CVD) receiving degarelix (GnRH receptor antagonist) or leuprolide (GnRH receptor agonist)

TPS395

Background: Epidemiological studies showed an association between GnRH agonists and a long-term increased risk of CVD, early after treatment initiation and with a higher risk seen in pts with pre-existing CVD. Retrospective pooled safety analyses of 6 randomized trials showed that significantly fewer pts treated with the GnRH receptor antagonists, degarelix, had a CV event or death compared with pts receiving a GnRH receptor agonist. In those studies showing an increased CV risk, Androgen-Deprivation Therapy (ADT) was primarily with GnRH receptor agonists. The mechanistic differences between GnRH antagonists and agonists, including testosterone surge and time to suppression at initiation, effect on follicle-stimulating hormone and on GnRH receptors e.g. T-lymphocytes in atherosclerotic plaque, raises the possibility of different CV risk profiles. The PRONOUNCE trial is the first to prospectively assess whether a GnRH agonist/antagonist can worsen pre-existing CVD; assess the impact of GnRH agonist/antagonist on CV risk biomarkers; and effects of hormonal therapy on immune system. Methods: PRONOUNCE is a multi-center, randomized, controlled trial of 900 men with pc and concomitant CVD, assessing adjudicated MACEs, i.e. myocardial infarction (fatal, non-fatal), stroke (fatal, non-fatal), or death in pts randomized 1:1 to either degarelix or leuprolide according to label recommendations for up to one year. Eligibility include pre-defined CVD, metastatic or locally advanced pc; high-risk disease with plan for definitive radiation therapy (RT); recurrence after local therapy with PSA doubling time <12 months; or salvage RT with neoadjuvant/adjuvant ADT for at least 12 months. Serum samples are collected for the analysis of various CV, inflammatory, and immune biomarkers. The primary endpoint will be based on Kaplan-Meier estimator of survival function and stratified for age group and region. Interim analysis is scheduled when 50% of MACE events have occurred allowing the DSMB to recommend for sample size correction. Clinical trial information: NCT02663908.

c15-153: Randomized phase IB/II study of enzalutamide with and without ribociclib in patients with metastatic castrate resistant, chemotherapy naïve prostate cancer that retains RB expression

TPS384

Background: Current data suggests RB function is often attenuated in tumors through hyperphosphorylation; thus, RB activity can be “re-awakened” in RB+ tumors by suppressing key kinases that phosphorylate RB (CDK4/6). Recent findings identified perturbations of the RB tumor suppressor as a major mechanism of androgen receptor (AR) deregulation and castration-resistant prostate cancer (CRPC) formation. Our preclinical studies indicate RB+ tumors are exquisitely responsive to CDK4/6 inhibitors, revealing tumor-specific cytostatic and cytotoxic effects. These analyses strongly support the use of CDK4/6 inhibitors to activate the RB pathway, and impede the transition to CRPC. We hypothesize the CDK4/6 inhibitor ribociclib (ribo) in combination with enzalutamide (enz) in patients (pts) with progressive metastatic CRPC (mCRPC) that retains RB expression will significantly increase the efficacy of enz. Methods: This is a phase IB/II study of pts with mCRPC with RB+ tumors who have not received chemotherapy. Since ribo and enz have not been combined together in pts, the standard doses of enz and a traditional 3x3 dose escalation schema will be used in phase I to establish the safe dose of the combination; this dose will be used in phase II. Since both drugs are metabolized via the liver, plasma concentrations of ribo and enz will be monitored. To determine if ribo will improve the clinical activity in pts treated with enz, a randomized (1:1) phase II study using enz as the control arm vs. the combination will follow. This study will evaluate an early clinical activity readout, thus the primary phase II endpoint will be a proportion of pts with ≥ 50% PSA decline at 12 weeks. Secondary endpoints are rPFS, PSA PFS, OS and safety. If there is clinical activity noted, further randomized testing will be required to establish ribo clinical benefit in combination with enz. 5 sites are participating, managed by the Prostate Cancer Clinical Trials Consortium. Dose Levels 1 and 2 have been completed without any DLTs in the phase I portion of the study. A review of Dose Level 3 is planned for October 2017. Clinical trial information: NCT02555189.

Sipuleucel-T: When and for Whom to Recommend It

Multiple immunotherapy platforms have been investigated for prostate cancer, but sipuleucel-T still remains the sole approved autologous cellular immune product that can be used in men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer. While preliminary data for specific checkpoint inhibitors suggest benefit for some patients, leading to durable responses, it has been clear that sipuleucel-T can affect not only the intratumoral milieu but also systemic immune populations. This means that the immune system can respond to sipuleucel-T in such a way that it may also effect an immunomodulatory response to other current and future treatments. It is clear that sipuleucel-T is here to stay; nevertheless, efforts to enhance its efficacy continue. A challenge that continues to be investigated is the question of how and when to use this immune therapy as part of the current continuum of competing approved agents.

The need for immune biomarkers for treatment prognosis and response in genitourinary malignancies

Immune biomarkers encompass a wide range of blood-borne and cell-associated molecules whose detection or expression may change in response to an immune therapy. These immune therapies encompass a range of platforms including autologous cellular products, in other words, dendritic cells, prime boost DNA vaccines, chimeric antigen receptor (CAR) T cells and checkpoint inhibitors. The response to checkpoint inhibitors by a particular cancer may not be necessarily associated with a change in a particular immune biomarker; other immune biomarkers are needed to assess their association with treatment response or a change in the biology that can impact on the immunologic milieu. How these potential biomarkers can be incorporated into clinical trial design, and their role in interrogating the immunologic milieu will be discussed.