Single Cell Analysis of Treatment-Resistant Prostate Cancer: Implications of Cell State Changes for Cell Surface Antigen Targeted Therapies

Targeting cell surface molecules using radioligand and antibody-based therapies has yielded considerable success across cancers. However, it remains unclear how the expression of putative lineage markers, particularly cell surface molecules, varies in the process of lineage plasticity, wherein tumor cells alter their identity and acquire new oncogenic properties. A notable example of lineage plasticity is the transformation of prostate adenocarcinoma (PRAD) to neuroendocrine prostate cancer (NEPC)--a growing resistance mechanism that results in the loss of responsiveness to androgen blockade and portends dismal patient survival. To understand how lineage markers vary across the evolution of lineage plasticity in prostate cancer, we applied single cell analyses to 21 human prostate tumor biopsies and two genetically engineered mouse models, together with tissue microarray analysis (TMA) on 131 tumor samples. Not only did we observe a higher degree of phenotypic heterogeneity in castrate-resistant PRAD and NEPC than previously anticipated, but also found that the expression of molecules targeted therapeutically, namely PSMA, STEAP1, STEAP2, TROP2, CEACAM5, and DLL3, varied within a subset of gene-regulatory networks (GRNs). We also noted that NEPC and small cell lung cancer (SCLC) subtypes shared a set of GRNs, indicative of conserved biologic pathways that may be exploited therapeutically across tumor types. While this extreme level of transcriptional heterogeneity, particularly in cell surface marker expression, may mitigate the durability of clinical responses to novel antigen-directed therapies, its delineation may yield signatures for patient selection in clinical trials, potentially across distinct cancer types.

Convergent evolution of BRCA2 reversion mutations under therapeutic pressure by PARP inhibition and platinum chemotherapy

Reversion mutations that restore wild-type function of the BRCA gene have been described as a key mechanism of resistance to Poly(ADP-ribose) polymerase (PARP) inhibitor therapy in BRCA-associated cancers. Here, we report a case of a patient with metastatic castration-resistant prostate cancer (mCRPC) with a germline BRCA2 mutation who developed acquired resistance to PARP inhibition. Extensive genomic interrogation of cell-free DNA (cfDNA) and tissue at baseline, post-progression, and postmortem revealed ten unique BRCA2 reversion mutations across ten sites. While several of the reversion mutations were private to a specific site, nine out of ten tumors contained at least one mutation, suggesting a powerful clonal selection for reversion mutations in the presence of therapeutic pressure by PARP inhibition. Variable cfDNA shed was seen across tumor sites, emphasizing a potential shortcoming of cfDNA monitoring for PARPi resistance. This report provides a genomic portrait of the temporal and spatial heterogeneity of prostate cancer under the selective pressure of a PARP inhibition and exposes limitations in the current strategies for detection of reversion mutations.

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.

Clinical Impact of a Rapid Genetic Testing Model for Advanced Prostate Cancer Patients

PURPOSE

Genetic testing may alter clinical management for individuals with metastatic prostate cancer by identifying additional therapies. Traditional counseling models are unlikely to enable time-sensitive therapeutic decision-making. This study aimed to determine the feasibility and clinical impact of an alternative hereditary genetic testing model.

MATERIALS AND METHODS

As part of a multicenter, single-arm prospective trial, individuals with advanced prostate cancer were referred by their oncologist for testing of 14 genes associated with hereditary prostate cancer. Pretest education (brochure and video) was provided in the oncology clinic. Questionnaires assessing participant satisfaction with both pretest education and decision to undergo genetic testing were collected. A genetic counselor contacted participants by phone to obtain family history and discuss results. Medical records were queried to determine whether a change in clinical management was discussed.

RESULTS

Of 501 participants consented to germline analysis, 51 (10.2%) had at least 1 pathogenic/likely pathogenic variant. Change in treatment was discussed with 22/48 (45.8%) of eligible participants who tested positive. Feasibility of this model was assessed by participant satisfaction and turnaround time. Average±SD satisfaction with the pretest education (15.5±2.2, 4-20 scale) and with the decision to undergo genetic testing (17.1±2.9, 4-20 scale) were both high. Results were returned 20 days (median) after sample collection.

CONCLUSIONS

Oncologist-initiated germline genetic testing in collaboration with a genetic counselor is a feasible approach to testing advanced prostate cancer patients with impactful clinical actionability. The testing model and educational material serve as resources to clinicians treating prostate cancer patients.

Management of patients with advanced prostate cancer-metastatic and/or castration-resistant prostate cancer: Report of the Advanced Prostate Cancer Consensus Conference (APCCC) 2022

BACKGROUND

Innovations in imaging and molecular characterisation together with novel treatment options have improved outcomes in advanced prostate cancer. However, we still lack high-level evidence in many areas relevant to making management decisions in daily clinical practise. The 2022 Advanced Prostate Cancer Consensus Conference (APCCC 2022) addressed some questions in these areas to supplement guidelines that mostly are based on level 1 evidence.

OBJECTIVE

To present the voting results of the APCCC 2022.

DESIGN, SETTING, AND PARTICIPANTS

The experts voted on controversial questions where high-level evidence is mostly lacking: locally advanced prostate cancer; biochemical recurrence after local treatment; metastatic hormone-sensitive, non-metastatic, and metastatic castration-resistant prostate cancer; oligometastatic prostate cancer; and managing side effects of hormonal therapy. A panel of 105 international prostate cancer experts voted on the consensus questions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The panel voted on 198 pre-defined questions, which were developed by 117 voting and non-voting panel members prior to the conference following a modified Delphi process. A total of 116 questions on metastatic and/or castration-resistant prostate cancer are discussed in this manuscript. In 2022, the voting was done by a web-based survey because of COVID-19 restrictions.

RESULTS AND LIMITATIONS

The voting reflects the expert opinion of these panellists and did not incorporate a standard literature review or formal meta-analysis. The answer options for the consensus questions received varying degrees of support from panellists, as reflected in this article and the detailed voting results are reported in the supplementary material. We report here on topics in metastatic, hormone-sensitive prostate cancer (mHSPC), non-metastatic, castration-resistant prostate cancer (nmCRPC), metastatic castration-resistant prostate cancer (mCRPC), and oligometastatic and oligoprogressive prostate cancer.

CONCLUSIONS

These voting results in four specific areas from a panel of experts in advanced prostate cancer can help clinicians and patients navigate controversial areas of management for which high-level evidence is scant or conflicting and can help research funders and policy makers identify information gaps and consider what areas to explore further. However, diagnostic and treatment decisions always have to be individualised based on patient characteristics, including the extent and location of disease, prior treatment(s), co-morbidities, patient preferences, and treatment recommendations and should also incorporate current and emerging clinical evidence and logistic and economic factors. Enrolment in clinical trials is strongly encouraged. Importantly, APCCC 2022 once again identified important gaps where there is non-consensus and that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference (APCCC) provides a forum to discuss and debate current diagnostic and treatment options for patients with advanced prostate cancer. The conference aims to share the knowledge of international experts in prostate cancer with healthcare providers worldwide. At each APCCC, an expert panel votes on pre-defined questions that target the most clinically relevant areas of advanced prostate cancer treatment for which there are gaps in knowledge. The results of the voting provide a practical guide to help clinicians discuss therapeutic options with patients and their relatives as part of shared and multidisciplinary decision-making. This report focuses on the advanced setting, covering metastatic hormone-sensitive prostate cancer and both non-metastatic and metastatic castration-resistant prostate cancer.

TWITTER SUMMARY

Report of the results of APCCC 2022 for the following topics: mHSPC, nmCRPC, mCRPC, and oligometastatic prostate cancer.

TAKE-HOME MESSAGE

At APCCC 2022, clinically important questions in the management of advanced prostate cancer management were identified and discussed, and experts voted on pre-defined consensus questions. The report of the results for metastatic and/or castration-resistant prostate cancer is summarised here.

Abstract NG10: Chromatin profiles classify castration-resistant prostate cancers suggesting therapeutic targets

Untreated prostate cancers rely on androgen receptor (AR) signaling for growth and survival, forming the basis for the initial efficacy of androgen deprivation therapy (ADT). Yet the disease can relapse and progress to a lethal stage termed castration-resistant prostate cancer (CRPC). Reactivation of AR signaling represents the most common driver of CRPC growth, and next-generation AR signaling inhibitors (ARSIs) are now used in combination with ADT as first-line therapy. However, ARSIs can result in selective pressure, thereby generating AR-independent tumors. The transition from AR dependence frequently accompanies a change in a phenotype resembling developmental transdifferentiation or “lineage plasticity”. Neuroendocrine prostate cancer, which lacks a defined pathologic classification, is the most studied type of lineage plasticity. However, most AR-null tumors do not exhibit neuroendocrine features and are classified as “double-negative prostate cancer”, the drivers of which are poorly defined. Lineage plasticity studies in CRPC are limited by the lack of genetically defined patient-derived models that recapitulate the disease spectrum. To address this, we developed a biobank of organoids generated from patient biopsies to study the landscape of metastatic CRPC and allow for functional validation assays. Proteins called transcription factors (TFs) are drivers of tumor lineage plasticity. To identify the key TFs that drive the growth of AR-independent tumors, we integrated epigenetic and transcriptomic data generated from CRPC models. We generated ATAC-seq (assay for transposase-accessible chromatin sequencing) and RNA-seq data from 22 metastatic human prostate cancer organoids, six patient-derived xenografts (PDXs), and 12 derived or traditional cell lines. We classified the 40 models into four subtypes and predicted key TFs of each subtype. Besides the well-characterized AR-dependent (CRPC-AR) and neuroendocrine subtypes (CRPC-NE), we identified two novel AR-negative/low groups, including a Wnt-dependent subtype (CRPC-WNT), driven by TCF/LEF TFs, and a stem cell-like (SCL) subtype (CRPC-SCL), driven by the AP-1 family of TFs. To apply the subtype classification to patient samples, we derived RNA-seq signatures from the organoids and applied them to 366 patient samples from two independent CRPC cohorts. The generated signatures recapitulated the four-subtype classification and revealed that CRPC-SCL is the second most prevalent group. Patients from CRPC-SCL are also associated with shorter time under ARSI treatment compared to CRPC-AR, indicating that the ARSI treatments were less effective for CRPC-SCL patients. Additional chromatin immunoprecipitation sequencing (ChIP-seq) analysis indicated that AP-1 (FOSL1) collaboratively binds with TEAD and transcription coactivators, YAP and TAZ. Knocking down of AP-1 (FOSL1), YAP/TAZ decreased cell growth of CRPC-SCL and showed a decrease of chromatin accessibility at CRPC-SCL-specific open chromatin sites and down-regulation of YAP/TAZ target gene expression. In addition, the expression of AP-1 (FOSL1) decreased upon YAP/TAZ knockdown suggesting a positive feedback loop as well as YAP/TAZ as actional targets in CRPC-SCL. We used two small-molecule inhibitors, verteporfin and T-5224, that act on the YAP/TAZ/AP-1 pathway for their potential use as therapeutics for CRPC-SCL tumors, both inhibited the growth of samples from CRPC-SCL but not CRPC-AR. By overexpressing an AP-1 family gene (FOSL1) in AR-high cells, we observed an increase in chromatin accessibility at CRPC-SCL-specific open chromatin sites as well as significant up-regulation of CRPC-SCL signature genes, suggesting that AP-1 functions as a pioneering factor and master regulator for CRPC-SCL. All this work was recently published in Science (Tang, Xu et al. Science, 2022) where I am the co-first author. In summary, by using a diverse biobank of organoids, PDXs, and cell lines that recapitulate the heterogeneity of metastatic prostate cancer, we created a map of the chromatin accessibility and transcriptomic landscape of CRPC. We validated the CRPC-AR and CRPC-NE subtypes and report two novel subtypes of AR-negative/low samples, CRPC-SCL and CRPC-WNT, as well as their respective key TFs. Additional analysis revealed a model in which YAP, TAZ, TEAD, and AP-1 function together and drive oncogenic growth in CRPC-SCL samples. In addition, we proposed small inhibitors of YAP and TAZ that can potentially be used to treat CRPC-SCL patients. Overall, our results show how the stratification of CRPC patients into four subtypes using their transcriptomes can potentially inform appropriate clinical decisions.

Citation Format: Fanying Tang, Duo Xu, Shangqian Wang, Chen Khuan Wong, Alexander Martinez-Fundichely, Cindy J. Lee, Sandra Cohen, Jane Park, Corinne E. Hill, Kenneth Eng, Rohan Bareja, Teng Han, Eric Minwei Liu, Ann Palladino, Wei Di, Dong Gao, Wassim Abida, Shaham Beg, Loredana Puca, Maximiliano Meneses, Elisa de Stanchina, Michael F. Berger, Anuradha Gopalan, Lukas E. Dow, Juan Miguel Mosquera, Himisha Beltran, Cora N. Sternberg, Ping Chi, Howard I. Scher, Andrea Sboner, Yu Chen, Ekta Khurana. Chromatin profiles classify castration-resistant prostate cancers suggesting therapeutic targets. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr NG10.

Abstract 941: Assessment of the completeness, accuracy, and scalability of commercial abstraction for a large prostate cancer biospecimen repository

Background: Large repositories of biospecimens collected from patients at cancer centers can provide a valuable resource in the development and validation of new biomarker assays to guide therapeutic decision-making. In order to utilize such repositories for biomarker studies, biospecimens must be annotated with the clinical context of each sample. The main source of clinical data is typically an unstructured electronic medical record, which can require a significant amount of time and resources to manually curate.

Methods: We developed a database comprised of disease-specific clinical data elements for a large repository of prostate cancer blood samples collected between 2006 – 2022 at a comprehensive cancer center. To provide clinical context for these samples, we contracted and trained a data abstraction company on entry practices with strict adherence to our standardized data dictionary and source hierarchy.

After data abstraction and review of an initial training set, we performed a formal evaluation of data quality (completeness and accuracy) through a 100-patient blinded comparison to gold-standard abstraction by a medical oncologist using all available data sources. Subsequently, data entry was completed for an additional 2500 patients and included in longitudinal analysis.

Results: Comparison to medical oncologist reference determined that the commercial annotations demonstrated similar completeness for most data elements. For some elements such as stage at diagnosis (M1 vs. M0), commercial abstraction achieved lower completeness (80%) than a medical oncologist (100%). Overall, the accuracy of the commercial annotations varied by element but was suitable for the purpose of identifying samples for use in context-specific biomarker studies. Data regarding disease-related events showed low median variance in the timing of first metastasis (0 months) and castration-resistance (-2.1 months), with substantial observed variance trending towards earlier event calling.

Longitudinal analysis of 2500 abstractions showed relatively stable completeness in staging data over time, suggesting that missing data is at least partially attributable to imposed restrictions in data source hierarchy rather than inexperience. Targeted retraining mid-way after 1300 annotations considerably increased the speed of data entry without noticeable changes in data completeness.

Conclusions: Commercial data abstraction can be effectively utilized to perform clinical data annotation for large biospecimen repositories with acceptable levels of completeness and accuracy. With appropriate training and direct oversight by an experienced on-site research team, this represents a scalable method for extracting valuable clinical data from largely unstructured patient medical records.

Citation Format: Emily A. Carbone, Ethan S. Barnett, Niamh M. Keegan, Samantha E. Vasselman, Barbara Nweji, Ria N. Gajar, Karen A. Autio, Wassim Abida, Howard I. Scher, Konrad H. Stopsack. Assessment of the completeness, accuracy, and scalability of commercial abstraction for a large prostate cancer biospecimen repository [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 941.

Management of Patients with Advanced Prostate Cancer. Part I: Intermediate-/High-risk and Locally Advanced Disease, Biochemical Relapse, and Side Effects of Hormonal Treatment: Report of the Advanced Prostate Cancer Consensus Conference 2022

BACKGROUND

Innovations in imaging and molecular characterisation and the evolution of new therapies have improved outcomes in advanced prostate cancer. Nonetheless, we continue to lack high-level evidence on a variety of clinical topics that greatly impact daily practice. To supplement evidence-based guidelines, the 2022 Advanced Prostate Cancer Consensus Conference (APCCC 2022) surveyed experts about key dilemmas in clinical management.

OBJECTIVE

To present consensus voting results for select questions from APCCC 2022.

DESIGN, SETTING, AND PARTICIPANTS

Before the conference, a panel of 117 international prostate cancer experts used a modified Delphi process to develop 198 multiple-choice consensus questions on (1) intermediate- and high-risk and locally advanced prostate cancer, (2) biochemical recurrence after local treatment, (3) side effects from hormonal therapies, (4) metastatic hormone-sensitive prostate cancer, (5) nonmetastatic castration-resistant prostate cancer, (6) metastatic castration-resistant prostate cancer, and (7) oligometastatic and oligoprogressive prostate cancer. Before the conference, these questions were administered via a web-based survey to the 105 physician panel members ("panellists") who directly engage in prostate cancer treatment decision-making. Herein, we present results for the 82 questions on topics 1-3.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Consensus was defined as ≥75% agreement, with strong consensus defined as ≥90% agreement.

RESULTS AND LIMITATIONS

The voting results reveal varying degrees of consensus, as is discussed in this article and shown in the detailed results in the Supplementary material. The findings reflect the opinions of an international panel of experts and did not incorporate a formal literature review and meta-analysis.

CONCLUSIONS

These voting results by a panel of international experts in advanced prostate cancer can help physicians and patients navigate controversial areas of clinical management for which high-level evidence is scant or conflicting. The findings can also help funders and policymakers prioritise areas for future research. Diagnostic and treatment decisions should always be individualised based on patient and cancer characteristics (disease extent and location, treatment history, comorbidities, and patient preferences) and should incorporate current and emerging clinical evidence, therapeutic guidelines, and logistic and economic factors. Enrolment in clinical trials is always strongly encouraged. Importantly, APCCC 2022 once again identified important gaps (areas of nonconsensus) that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference (APCCC) provides a forum to discuss and debate current diagnostic and treatment options for patients with advanced prostate cancer. The conference aims to share the knowledge of international experts in prostate cancer with health care providers and patients worldwide. At each APCCC, a panel of physician experts vote in response to multiple-choice questions about their clinical opinions and approaches to managing advanced prostate cancer. This report presents voting results for the subset of questions pertaining to intermediate- and high-risk and locally advanced prostate cancer, biochemical relapse after definitive treatment, advanced (next-generation) imaging, and management of side effects caused by hormonal therapies. The results provide a practical guide to help clinicians and patients discuss treatment options as part of shared multidisciplinary decision-making. The findings may be especially useful when there is little or no high-level evidence to guide treatment decisions.

Automated analysis of FDG-PET/CT imaging to monitor heterogeneous disease response in metastatic castration-resistant prostate cancer

251

Background: The heterogeneity of individual sites of disease in prostate cancer is well recognized and increases over time as the therapies administered promote divergent evolution. In clinical practice, this is often depicted in radiology reports as a mixed response, wherein some lesions improve and others progress or emerge, for which individualizing management is challenging. The problem is exacerbated in patients with high volume disease by the inability to concisely and effectively assess overall disease status which may mask the presence of emerging resistance that could benefit from early intervention and/or a change in therapy. Methods: Thirty-one sets of serial baseline and on-treatment FDG-PET/CT images done for the clinical management of patients with progressing mCRPC were analyzed using TRAQinform IQ software (AIQ Solutions). Individual regions of interest (ROI) identified and tracked across imaging time-points were analyzed for a range of features. The univariate prognostic weight of each feature was assessed with Cox regression models. Imaging features from single timepoints, heterogeneity of response features, and PSA values/dynamics were input into the separate TRAQinform Profile software, which was calculated to predict either time on treatment or overall survival using 3-fold cross-validation of a random survival forest. Individual case reviews were performed on select patients including TRAQinform IQ analytics, PSA trends, radiology reports, and physician notes to evaluate the potential additive benefit of the TRAQinform IQ output. Results: In general, imaging features were more strongly correlated with overall survival than PSA dynamics. After iterative feature selection, only imaging features were selected for TRAQinform Profile scores. In the case of predicting OS, the most important features were baseline total lesion glycolysis (TLG), and the number of new/progressing lesions. Patients with high TRAQinform Profile scores had shorter median survival times than those with low scores (630 vs 1326 days, p<0.01, c-index = 0.744). Of particular value was the finding that the software could identify indicators of oligo-progression for which directed radiotherapy could be considered. Also detected were early indications of widespread disease progression represented as changes in total SUV uptake and TRAQinform Profile scores, which could indicate that the patient was no longer benefitting from treatment and a change in therapy was needed. Conclusions: In pilot analysis, the TRAQinform Profile scores generated from baseline and early on-treatment FDG-PET images had treatment-agnostic prognostic value in mCRPC. Further validation is on-going. The TRAQinform IQ software can aid in identifying the presence of resistant lesions in the setting of otherwise grossly stable disease as determined by the treating physician.

A phase 2 study of immunogenic cell death inducer PT-112 in patients with metastatic castration-resistant prostate cancer

TPS292

Background: PT-112 is a novel small I-O molecule currently in development for several cancers. Preclinical studies have shown the robust induction of immunogenic cell death by PT-112, leading to an anti-cancer adaptive immune response. Biodistribution experiments in mice showed PT-112’s partial bone affinity. In two prior phase I studies, late-line metastatic castration-resistant prostate cancer patients (mCRPC pts) were treated with evidence of anti-cancer activity, including tumor volume reductions, improvements in PET and bone scans, PSA and alkaline phosphatase (ALP) reductions, and anecdotal cases of improvement in disease-related pain. This, taken together with the immunogenic and osteotropic properties observed in preclinical work, provided a strong rationale to further explore PT-112 in mCRPC, an immunologically “cold” disease with a high prevalence of bone metastases. Moreover, in an analysis of >6,000 mCRPC pts, circulating tumor cell (CTC) declines (CTC0 and CTC conversions) were correlated with improvements in survival to a greater extent than PSA declines (PSA50) (Heller et al., JCO, 36:6 2017), prompting incorporation of CTC changes as a secondary endpoint. Methods: The primary objective of the study is to define the dose regimen of PT-112 for pivotal study. Pts are randomized to one of three arms, receiving IV PT-112 on 28-day cycles via one hour infusions on (1) Days 1 and 15 at 250 mg/m2, (2) Days 1 and 15 at 360 mg/m2, or (3) Days 1 and 15 of cycle 1 at 360 mg/m2 followed by 250 mg/m2 on Day 15 of subsequent cycles. Key eligibility criteria include radiographically progressive disease at study entry; ≥3 life-prolonging therapies for metastatic disease including 1-2 taxanes, ≥1 new generation anti-androgen therapies, and other drugs FDA approved on the basis of survival; and allowing bone-only metastatic disease. Efficacy assessments comprise disease control rate at 4 months (DCR4) using RECIST and PCWG3 criteria, objective response rate, CTC0 and CTC conversion, PSA50 and ALP reductions. Additionally, T cell receptor sequencing is conducted to characterize treatment-induced changes in T cell fraction and clonal expansions, as a means of generating meaningful supportive data on the immune mechanism of PT-112 monotherapy. A Fleming two-stage design will be used to assess each arm, with a 20% DCR4 as the null hypotheses, requiring ≥6 of 25 pts responding in stage one and ≥14 of 45 in total to reject the null. In addition, other efficacy measures, such as CTC responses, as well as exposure/response and exposure/safety analyses will be applied to characterize the risk/benefit ratio and select the optimal dose regimen for PT-112. As of October 11th, 2022, 38 pts have been enrolled out of a planned maximum of 135. Clinical trial information: NCT02266745 .

Analysis of BRCA2 Copy Number Loss and Genomic Instability in Circulating Tumor Cells from Patients with Metastatic Castration-resistant Prostate Cancer

BACKGROUND

BRCA2 alterations predict for a response to poly-ADP-ribose polymerase inhibition in metastatic castration-resistant prostate cancer (mCRPC). However, detection is hindered by insufficient tumor tissue and low sensitivity of cell-free DNA for detecting copy number loss.

OBJECTIVE

To evaluate the BRCA2 loss detection using single-cell, shallow whole-genome sequencing (sWGS) of circulating tumor cells (CTCs) in patients with mCRPC.

DESIGN, SETTING, AND PARTICIPANTS

We analyzed CTC samples collected concurrently with tumor biopsies intended for clinical sequencing in patients with progressing mCRPC.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Differences in proportions were evaluated using the chi-square test. Correlations between assays were analyzed in linear regression models. Associations between alterations and genomic instability were assessed on the single-cell level using mixed-effect negative binomial models.

RESULTS AND LIMITATIONS

We identified 138 patients with concurrent CTC and biopsy samples. CTC sWGS generated copy number profiles in a similar proportion of patients to biopsy samples (83% vs 78%, p = 0.23), but was more effective than bone biopsies (79% vs 50%; p = 0.009). CTC sWGS detected BRCA2 loss in more patients than tissue at the ≥1 (42% vs 16%; p < 0.001) and ≥2 (27% vs 16%; p = 0.028) CTC thresholds. The overall prevalence of BRCA2 loss was not increased in CTCs using sample-level composite z scores (p = 0.4), but was significantly increased compared with a lower-than-expected prevalence in bone samples (21% vs 3%, p = 0.014). Positive/negative predictive values for CTC BRCA2 loss were 89%/96% using the ≥1 CTC threshold and 67%/92% using the composite z score. CTC BRCA2 loss was associated with higher genomic instability in univariate (1.4-fold large-scale transition difference, 95% confidence interval [CI]: 1.2-1.6; p < 0.001) and multivariable analysis (1.4-fold difference, 95% CI: 1.2-1.6; p < 0.001).

CONCLUSIONS

Copy number profiles can reliably be generated using CTC sWGS, which detected a majority of tissue-confirmed BRCA2 loss and "CTC-only" losses. BRCA2 losses were supported by increases in genomic instability.

PATIENT SUMMARY

Current testing strategies have limitations in their ability to detect BRCA2 loss, a relatively common alteration in prostate cancer that is used to identify patients who may benefit from targeted therapy. In this paper, we evaluated whether we could detect BRCA2 loss in individual tumor cells isolated from patient blood samples and found this method to be suitable for further analysis.

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.

Evaluation of an Integrated Spectroscopy and Classification Platform for Point-of-Care Core Needle Biopsy Assessment: Performance Characteristics from Ex Vivo Renal Mass Biopsies

PURPOSE

To evaluate a transmission optical spectroscopy instrument for rapid ex vivo assessment of core needle cancer biopsies (CNBs) at the point of care.

MATERIALS AND METHODS

CNBs from surgically resected renal tumors and nontumor regions were scanned on their sampling trays with a custom spectroscopy instrument. After extracting principal spectral components, machine learning was used to train logistic regression, support vector machines, and random decision forest (RF) classifiers on 80% of randomized and stratified data. The algorithms were evaluated on the remaining 20% of the data set held out during training. Binary classification (tumor/nontumor) was performed based on a decision threshold. Multinomial classification was also performed to differentiate between the subtypes of renal cell carcinoma (RCC) and account for potential confounding effects from fat, blood, and necrotic tissue. Classifiers were compared based on sensitivity, specificity, and positive predictive value (PPV) relative to a histopathologic standard.

RESULTS

A total of 545 CNBs from 102 patients were analyzed, yielding 5,583 spectra after outlier exclusion. At the individual spectra level, the best performing algorithm was RF with sensitivities of 96% and 92% and specificities of 90% and 89%, for the binary and multiclass analyses, respectively. At the full CNB level, RF algorithm also showed the highest sensitivity and specificity (93% and 91%, respectively). For RCC subtypes, the highest sensitivity and PPV were attained for clear cell (93.5%) and chromophobe (98.2%) subtypes, respectively.

CONCLUSIONS

Ex vivo spectroscopy imaging paired with machine learning can accurately characterize renal mass CNB at the time of tissue acquisition.

Overall survival with circulating tumor DNA-guided therapy in advanced non-small-cell lung cancer

Circulating tumor DNA (ctDNA) sequencing guides therapy decisions but has been studied mostly in small cohorts without sufficient follow-up to determine its influence on overall survival. We prospectively followed an international cohort of 1,127 patients with non-small-cell lung cancer and ctDNA-guided therapy. ctDNA detection was associated with shorter survival (hazard ratio (HR), 2.05; 95% confidence interval (CI), 1.74-2.42; P < 0.001) independently of clinicopathologic features and metabolic tumor volume. Among the 722 (64%) patients with detectable ctDNA, 255 (23%) matched to targeted therapy by ctDNA sequencing had longer survival than those not treated with targeted therapy (HR, 0.63; 95% CI, 0.52-0.76; P < 0.001). Genomic alterations in ctDNA not detected by time-matched tissue sequencing were found in 25% of the patients. These ctDNA-only alterations disproportionately featured subclonal drivers of resistance, including RICTOR and PIK3CA alterations, and were associated with short survival. Minimally invasive ctDNA profiling can identify heterogeneous drivers not captured in tissue sequencing and expand community access to life-prolonging therapy.

A clinical-grade liquid biomarker detects neuroendocrine differentiation in prostate cancer

BackgroundNeuroendocrine prostate cancer (NEPC) is an aggressive subtype, the presence of which changes the prognosis and management of metastatic prostate cancer.MethodsWe performed analytical validation of a Circulating Tumor Cell (CTC) multiplex RNA qPCR assay to identify the limit of quantification (LOQ) in cell lines, synthetic cDNA, and patient samples. We next profiled 116 longitudinal samples from a prospectively collected institutional cohort of 17 patients with metastatic prostate cancer (7 NEPC, 10 adenocarcinoma) as well as 265 samples from 139 patients enrolled in 3 adenocarcinoma phase II trials of androgen receptor signaling inhibitors (ARSIs). We assessed a NEPC liquid biomarker via the presence of neuroendocrine markers and the absence of androgen receptor (AR) target genes.ResultsUsing the analytical validation LOQ, liquid biomarker NEPC detection in the longitudinal cohort had a per-sample sensitivity of 51.35% and a specificity of 91.14%. However, when we incorporated the serial information from multiple liquid biopsies per patient, a unique aspect of this study, the per-patient predictions were 100% accurate, with a receiver-operating-curve (ROC) AUC of 1. In the adenocarcinoma ARSI trials, the presence of neuroendocrine markers, even while AR target gene expression was retained, was a strong negative prognostic factor.ConclusionOur analytically validated CTC biomarker can detect NEPC with high diagnostic accuracy when leveraging serial samples that are only feasible using liquid biopsies. Patients with expression of NE genes while retaining AR-target gene expression may indicate the transition to neuroendocrine differentiation, with clinical characteristics consistent with this phenotype.FundingNIH (DP2 OD030734, 1UH2CA260389, R01CA247479, and P30 CA014520), Department of Defense (PC190039 and PC200334), and Prostate Cancer Foundation (Movember Foundation - PCF Challenge Award).

The Impact of PIK3R1 Mutations and Insulin-PI3K-Glycolytic Pathway Regulation in Prostate Cancer

PURPOSE

Oncogenic alterations of the PI3K/AKT pathway occur in >40% of patients with metastatic castration-resistant prostate cancer, predominantly via PTEN loss. The significance of other PI3K pathway components in prostate cancer is largely unknown.

EXPERIMENTAL DESIGN

Patients in this study underwent tumor sequencing using the MSK-IMPACT clinical assay to capture single-nucleotide variants, insertions, and deletions; copy-number alterations; and structural rearrangements, or were profiled through The Cancer Genome Atlas. The association between PIK3R1 alteration/expression and survival was evaluated using univariable and multivariable Cox proportional-hazards regression models. We used the siRNA-based knockdown of PIK3R1 for functional studies. FDG-PET/CT examinations were performed with a hybrid positron emission tomography (PET)/CT scanner for some prostate cancer patients in the MSK-IMPACT cohort.

RESULTS

Analyzing 1,417 human prostate cancers, we found a significant enrichment of PIK3R1 alterations in metastatic cancers compared with primary cancers. PIK3R1 alterations or reduced mRNA expression tended to be associated with worse clinical outcomes in prostate cancer, particularly in primary disease, as well as in breast, gastric, and several other cancers. In prostate cancer cell lines, PIK3R1 knockdown resulted in increased cell proliferation and AKT activity, including insulin-stimulated AKT activity. In cell lines and organoids, PIK3R1 loss/mutation was associated with increased sensitivity to AKT inhibitors. PIK3R1-altered patient prostate tumors had increased uptake of the glucose analogue 18F-fluorodeoxyglucose in PET imaging, suggesting increased glycolysis.

CONCLUSIONS

Our findings describe a novel genomic feature in metastatic prostate cancer and suggest that PIK3R1 alteration may be a key event for insulin-PI3K-glycolytic pathway regulation in prostate cancer.

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.

What Experts Think About Prostate Cancer Management During the COVID-19 Pandemic: Report from the Advanced Prostate Cancer Consensus Conference 2021

Patients with advanced prostate cancer (APC) may be at greater risk for severe illness, hospitalisation, or death from coronavirus disease 2019 (COVID-19) due to male gender, older age, potential immunosuppressive treatments, or comorbidities. Thus, the optimal management of APC patients during the COVID-19 pandemic is complex. In October 2021, during the Advanced Prostate Cancer Consensus Conference (APCCC) 2021, the 73 voting members of the panel members discussed and voted on 13 questions on this topic that could help clinicians make treatment choices during the pandemic. There was a consensus for full COVID-19 vaccination and booster injection in APC patients. Furthermore, the voting results indicate that the expert's treatment recommendations are influenced by the vaccination status: the COVID-19 pandemic altered management of APC patients for 70% of the panellists before the vaccination was available but only for 25% of panellists for fully vaccinated patients. Most experts (71%) were less likely to use docetaxel and abiraterone in unvaccinated patients with metastatic hormone-sensitive prostate cancer. For fully vaccinated patients with high-risk localised prostate cancer, there was a consensus (77%) to follow the usual treatment schedule, whereas in unvaccinated patients, 55% of the panel members voted for deferring radiation therapy. Finally, there was a strong consensus for the use of telemedicine for monitoring APC patients. PATIENT SUMMARY: In the Advanced Prostate Cancer Consensus Conference 2021, the panellists reached a consensus regarding the recommendation of the COVID-19 vaccine in prostate cancer patients and use of telemedicine for monitoring these patients.

Statin and metformin use and outcomes in patients with castration-resistant prostate cancer treated with enzalutamide: A meta-analysis of AFFIRM, PREVAIL and PROSPER

BACKGROUND

Statins and metformin are commonly prescribed for patients, including those with prostate cancer. Preclinical and epidemiologic studies of each agent have suggested anti-cancer properties.

METHODS

Patient data from three randomised, double-blind, placebo-controlled, phase III studies evaluating enzalutamide (AFFIRM, PREVAIL and PROSPER) in patients with castration-resistant prostate cancer were included in this analysis. This post hoc, retrospective study examined the association of statin and metformin on radiographic progression-free survival (rPFS), metastasis-free survival (MFS), toxicity and overall survival (OS). After adjusting for available clinical prognostic variables, multivariate analyses were performed on pooled data from AFFIRM and PREVAIL, all three trials pooled, and each trial individually, to assess differential efficacy in these end-points associated with the baseline use of these medications.

RESULTS

In the multivariate analysis of the individual trials, OS and rPFS/MFS were not significantly influenced by statin or metformin use in AFFIRM or PROSPER. However, in PREVAIL, OS was significantly influenced by statin (hazard ratio [HR] 0.72; 95% confidence interval [CI] 0.59-0.89) and rPFS was significantly influenced by metformin (HR, 0.48; 95% CI 0.34-0.70). In pooled analyses, improved OS was significantly associated with statin use but not metformin use for AFFIRM+PREVAIL trials (HR 0.83; 95% CI 0.72-0.96) and AFFIRM+PREVAIL+PROSPER (HR 0.75; 95% CI 0.66-0.85).

CONCLUSIONS

The association between statin or metformin use and rPFS, MFS and OS was inconsistent across three trials. Analyses of all three trials pooled and AFFIRM+PREVAIL pooled revealed that statin but not metformin use was significantly associated with a reduced risk of death in enzalutamide-treated patients. Additional prospective, controlled studies are warranted.

CLINICAL TRIAL REGISTRATION

AFFIRM (NCT00974311), PREVAIL (NCT01212991) and PROSPER (NCT02003924).

Management of Patients with Advanced Prostate Cancer: Report from the Advanced Prostate Cancer Consensus Conference 2021

BACKGROUND

Innovations in treatments, imaging, and molecular characterisation in advanced prostate cancer have improved outcomes, but various areas of management still lack high-level evidence to inform clinical practice. The 2021 Advanced Prostate Cancer Consensus Conference (APCCC) addressed some of these questions to supplement guidelines that are based on level 1 evidence.

OBJECTIVE

To present the voting results from APCCC 2021.

DESIGN, SETTING, AND PARTICIPANTS

The experts identified three major areas of controversy related to management of advanced prostate cancer: newly diagnosed metastatic hormone-sensitive prostate cancer (mHSPC), the use of prostate-specific membrane antigen ligands in diagnostics and therapy, and molecular characterisation of tissue and blood. A panel of 86 international prostate cancer experts developed the programme and the consensus questions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The panel voted publicly but anonymously on 107 pre-defined questions, which were developed by both voting and non-voting panel members prior to the conference following a modified Delphi process.

RESULTS AND LIMITATIONS

The voting reflected the opinions of panellists and did not incorporate a standard literature review or formal meta-analysis. The answer options for the consensus questions received varying degrees of support from panellists, as reflected in this article and the detailed voting results reported in the Supplementary material.

CONCLUSIONS

These voting results from a panel of experts in advanced prostate cancer can help clinicians and patients to navigate controversial areas of management for which high-level evidence is scant. However, diagnostic and treatment decisions should always be individualised according to patient characteristics, such as the extent and location of disease, prior treatment(s), comorbidities, patient preferences, and treatment recommendations, and should also incorporate current and emerging clinical evidence and logistic and economic constraints. Enrolment in clinical trials should be strongly encouraged. Importantly, APCCC 2021 once again identified salient questions that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference is a forum for discussing current diagnosis and treatment options for patients with advanced prostate cancer. An expert panel votes on predefined questions focused on the most clinically relevant areas for treatment of advanced prostate cancer for which there are gaps in knowledge. The voting results provide a practical guide to help clinicians in discussing treatment options with patients as part of shared decision-making.

Automated Bone Scan Index to Optimize Prostate Cancer Working Group Radiographic Progression Criteria for Men With Metastatic Castration-Resistant Prostate Cancer

INTRODUCTION

Radiographic progression-free survival (rPFS) by Prostate Cancer Working Group (PCWG) criteria is a radiographic endpoint. The automated bone scan index (aBSI) quantifies osseous disease burden on bone scintigraphy as a percentage of total skeletal weight. Using the aBSI, we sought to quantify increase in tumor burden represented by PCWG progression criteria, and to determine the interval increase that best associates with overall survival (OS).

PATIENT AND METHODS

Retrospective analysis of trials using androgen receptor axis-targeted drugs for metastatic castration resistant prostate cancer patients (mCRPC). aBSI increase in bone disease was assessed from baseline scan to time-to-progression (per PCWG criteria). Threshold for time to aBSI increase were explored and the association between each time-to-threshold and OS was computed.

RESULTS

A total of 169 mCPRC patients had bone scans available for aBSI analysis. Of these, 90 (53%) had progression in bone meeting PCWG criteria. Total aBSI increase in patients meeting PCWG criteria was 1.22 (interquartile range [IQR]: 0.65-2.49), with a median relative increase of 109% (IQR: 40%-377%). Median aBSI at baseline was 3.1 (IQR: 1.3-7.1). The best association between OS and time-to-progression occurred with an absolute increase in aBSI equal to 0.6 (Kendall's tau 0.52).

CONCLUSION

An absolute increase of 0.6 or more in aBSI from the first follow-up scan results in the highest association with OS in patients with mCRPC. The rPFS by PCWG, identified progression at nearly twice this tumor burden, suggesting that aBSI may be used to further develop the PCWG criteria without degrading its association with OS.

Genomic alterations and evolution in patients with prostate cancer with histologic evidence of neuroendocrine differentiation

5029

Background: The incidence of transformation to neuroendocrine prostate cancer (NEPC) has increased in castration resistant prostate cancer (CRPC) in parallel with treatment advances inhibiting androgen receptor signaling. The current understanding is that this occurs in ̃10-20% of CRPC cases. Missing is a determination of the timing of molecular events that drive the process. Methods: Under an IRB-approved protocol, retrospective annotation of all MSK-reviewed pathology reports was conducted for 1447 prostate cancer patients with MSK-IMPACT sequencing data. For patients with pathologically confirmed NEPC, the date of the first sample with unequivocally reported NEPC (described as “neuroendocrine carcinoma” or as having “neuroendocrine differentiation” or “neuroendocrine features”) was recorded. Patients with early signs of histologic transformation not specifically reported as NEPC (double negative prostate cancer or rare/focal staining for NE markers) were analyzed separately. Sequencing results were described by castration-status at collection (CRPC vs castration-sensitive) and, if applicable, the relationship to NEPC diagnosis (i.e. pre- vs post-NEPC). Genomic enrichment analysis was used to identify differentially altered genes between groups. Results: In total, 95 (6.6%) patients had pathologically confirmed NEPC during their disease course, from whom 150 samples with sequencing results were available: including 18 patients with matched pre- and post-NEPC samples. CRPC samples from patients with NEPC (n = 70) were significantly enriched for RB1 alterations (50% vs 12%, p < 10-10, q < 10-10). AR alterations were significantly enriched in CRPC samples from patients without NEPC (n = 380) (63% vs 21%, p < 10-10, q < 1.27*10-8). Further, alterations in numerous genes including TP53, AMER1, ARID5B, YAP1, SOX2, and NKX2.1 were enriched in NEPC patients at the 95% confidence interval (CI) without correction for repeat testing. Matched pre- and post-NEPC samples demonstrated that TP53 alterations in post-NEPC samples are detected in the majority of pre-NEPC samples (8 of 10 patients), but RB1 alterations in post-NEPC samples are detected in a minority of pre-NEPC samples (1 of 8 patients). 54 (3.7%) patients had evidence of early histologic transformation. CRPC samples from these patients (n = 29) were enriched for mutations in RB1, MAP2K2, MUTYH, and CTNNB1 at the 95% CI without correction. FOXA1 mutations were enriched in patients without transformation. Conclusions: RB1, consistent with previous findings, is enriched in NEPC. The inability to detect RB1 alterations in pre-NEPC samples supports divergent evolution, although technical limits of tissue panel sequencing make it difficult to rule out the presence of sub-clonal alterations. Further study of additional genes which contribute to histologic transformation and the development of NEPC is warranted.

Chromosomal instability (CIN) in circulating tumor cells (CTC) predicts for taxane sensitivity in metastatic castration-resistant prostate cancer (mCRPC)

5026

Background: Few clinically validated biomarkers can inform therapy (tx) sequencing in mCRPC. Previously, we credentialed a biomarker of CIN in individual CTCs using phenotypic identification of cells with ≥9 large scale transitions (LSTs) and classification of CIN as high when detected in ≥3 CTC/mL (CIN3+). CIN3+ was associated with shorter radiographic progression survival (rPFS) and overall survival (OS) following taxane (T) or androgen receptor signaling inhibitor (ARSi) tx in mCRPC. Similarly, high CIN defined as ≥1 CTC/mL with ≥9 LSTs (CIN1+) predicts worse rPFS and OS following ARSi. Here, we explored if CIN1+ or CIN3+ predicted differential outcomes in pts on-tx with T or ARSi for mCRPC. Methods: We analyzed 208 banked CTC samples from 173 mCRPC pts collected within 30 days prior to starting a new tx with either T (n=88) or ARSi (n=120) in 2012-2017. CTCs were detected using Epic Sciences platform and CIN defined using the phenotypic classifier (PMID 32816908). Retrospective clinical annotation was completed for OS, defined as time from index tx start date to death, and rPFS, defined as index date to date of new or/and increasing lesion size in on-tx radiology report or death. Associations with rPFS and OS were studied according to samples’ CIN1+ and CIN3+ status. T vs. ARSi comparisons were adjusted using Cox models that incorporated pre-tx covariates, i.e. prior T or ARSi txs, total CTC count, presence of visceral disease, and prognostic lab values. Results: The median (range) follow-up from tx start to date of death or last follow-up was 7 (5-9) years. There were 53/120 (44%) pts starting ARSi that had prior ARSi txs and 41/88 (46%) pts starting taxane that had prior taxane txs. CTCs were detected in 184 (88%) samples, CIN1+ in 73 (35%; 64% pre-T, 36% pre-ARSi), and CIN3+ in 47 (22%; 60% pre-T,40% pre-ARSi). Compared to CIN1+, model results (Table) suggest that CIN3+ predicts a longer rPFS (p<0.01), and possibly OS (p=0.05), with T therapy. Compared to CIN1-, CIN3- also predicts a longer OS with ARSi therapy (p=0.04). Conclusions: CIN3+ CTC may be a more discriminating predictive biomarker than CIN1+ to help guide selection of T or ARSi tx in pts with mCRPC. Adequately powered prospective studies are planned. [Table: see text]

Chromatin profiles classify castration-resistant prostate cancers suggesting therapeutic targets

In castration-resistant prostate cancer (CRPC), the loss of androgen receptor (AR) dependence leads to clinically aggressive tumors with few therapeutic options. We used ATAC-seq (assay for transposase-accessible chromatin sequencing), RNA-seq, and DNA sequencing to investigate 22 organoids, six patient-derived xenografts, and 12 cell lines. We identified the well-characterized AR-dependent and neuroendocrine subtypes, as well as two AR-negative/low groups: a Wnt-dependent subtype, and a stem cell-like (SCL) subtype driven by activator protein-1 (AP-1) transcription factors. We used transcriptomic signatures to classify 366 patients, which showed that SCL is the second most common subtype of CRPC after AR-dependent. Our data suggest that AP-1 interacts with the YAP/TAZ and TEAD proteins to maintain subtype-specific chromatin accessibility and transcriptomic landscapes in this group. Together, this molecular classification reveals drug targets and can potentially guide therapeutic decisions.

Optimal Strategy and Benefit of Pulsed Therapy Depend On Tumor Heterogeneity and Aggressiveness at Time of Treatment Initiation

Therapeutic resistance is a fundamental obstacle in cancer treatment. Tumors that initially respond to treatment may have a preexisting resistant subclone or acquire resistance during treatment, making relapse theoretically inevitable. Here, we investigate treatment strategies that may delay relapse using mathematical modeling. We find that for a single-drug therapy, pulse treatment-short, elevated doses followed by a complete break from treatment-delays relapse compared with continuous treatment with the same total dose over a length of time. For tumors treated with more than one drug, continuous combination treatment is only sometimes better than sequential treatment, while pulsed combination treatment or simply alternating between the two therapies at defined intervals delays relapse the longest. These results are independent of the fitness cost or benefit of resistance, and are robust to noise. Machine-learning analysis of simulations shows that the initial tumor response and heterogeneity at the start of treatment suffice to determine the benefit of pulsed or alternating treatment strategies over continuous treatment. Analysis of eight tumor burden trajectories of breast cancer patients treated at Memorial Sloan Kettering Cancer Center shows the model can predict time to resistance using initial responses to treatment and estimated preexisting resistant populations. The model calculated that pulse treatment would delay relapse in all eight cases. Overall, our results support that pulsed treatments optimized by mathematical models could delay therapeutic resistance.

Optimizing the future: how mathematical models inform treatment schedules for cancer

For decades, mathematical models have influenced how we schedule chemotherapeutics. More recently, mathematical models have leveraged lessons from ecology, evolution, and game theory to advance predictions of optimal treatment schedules, often in a personalized medicine manner. We discuss both established and emerging therapeutic strategies that deviate from canonical standard-of-care regimens, and how mathematical models have contributed to the design of such schedules. We first examine scheduling options for single therapies and review the advantages and disadvantages of various treatment plans. We then consider the challenge of scheduling multiple therapies, and review the mathematical and clinical support for various conflicting treatment schedules. Finally, we propose how a consilience of mathematical and clinical knowledge can best determine the optimal treatment schedules for patients.

The Effect of Corticosteroids on Prostate Cancer Outcome Following Treatment with Enzalutamide: A Multivariate Analysis of the Phase III AFFIRM Trial

PURPOSE

The clinical impact of concurrent corticosteroid use (CCU) on enzalutamide-treated patients with metastatic castration-resistant prostate cancer (mCRPC) is unknown. We investigated the association of CCU with overall survival (OS), radiographic progression-free survival (rPFS), and time to prostate-specific antigen progression (TTPP) in post-chemotherapy, enzalutamide-treated patients with mCRPC.

PATIENTS AND METHODS

Post hoc analysis of AFFIRM (NCT00974311) with patients (n = 1,199) randomized 2:1 to enzalutamide 160 mg/day or placebo. Treatment group, CCU, and known prognostic factors were evaluated for impact on OS, rPFS, and TTPP using a multivariate Cox proportional hazards model. CCU was defined as "baseline" (use started at baseline) or "on-study" (baseline plus use that was started during the trial).

RESULTS

Enzalutamide significantly improved OS, rPFS, and TTPP independent of baseline CCU but was associated with inferior clinical outcomes when compared with no baseline CCU, including a shorter OS [10.8 months vs. not reached (NR); HR for use vs. no use, 2.13; 95% confidence interval (CI), 1.79-2.54], rPFS (5.2 months vs. 8.0 months; HR, 1.49; 95% CI, 1.29-1.72], and TTPP (4.6 months vs. 5.7 months; HR, 1.50; 95% CI, 1.25-1.81). These findings held in a multivariate analysis adjusting for baseline prognostic factors wherein baseline CCU was independently associated with decreased OS (HR, 1.71; 95% CI, 1.43-2.04; P < 0.0001) and rPFS (HR, 1.28; 95% CI, 1.11-1.48; P = 0.0007).

CONCLUSIONS

Patients with mCRPC benefited from enzalutamide treatment independent of CCU, but CCU was associated with worse baseline prognostic factors and outcomes.

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.

Spine Pain and Metastatic Prostate Cancer: Defining the Contribution of Nonmalignant Etiologies

PURPOSE

In patients with metastatic prostate cancer (MPC), the contribution of nonmalignant etiologies to morbidity is often overlooked.

METHODS

We retrospectively reviewed the documented specialist assessments of back pain in men with MPC in a joint medical oncology and physiatry clinic at our tertiary cancer care center. Data on cancer disease extent, hormonal status, sites of spread, pain characteristics, physiatric examination findings, imaging, and recommended management were reviewed, extracted, and codified. For those with back pain at a site of known disease, pain etiology was classified as malignant, nonmalignant, or mixed.

RESULTS

Ninety-three men were collaboratively assessed for back pain, 24 (26%) with a biochemical recurrence and 69 (74%) with MPC of whom 53 (77%) reported pain in an area of known spinal metastases including 35 (66%) metastatic castration-resistant disease and 34 (64%) a precancer history of back pain. The presenting pain symptoms of the 53 patients were activity-related in 22 (42%), radicular in eight (15%), transitional movement-related in seven (13%), biologic in five (9%), and multifactorial in 11 (21%). Overall, pain was deemed malignant in 20 (38%; five castration-sensitive, 15 metastatic castration resistant prostate cancer), nonmalignant in 12 (23%; four castration-sensitive, eight CRPC), and of mixed etiology in 21 (40%; nine castration-sensitive, 12 CRPC).

CONCLUSION

Nonmalignant etiologies contributed significantly to back pain at sites of metastatic spread for 33/53 (62%) patients with MPC assessed by medical oncology and physiatry. We recommend multidisciplinary care for patients with MPC and back pain to address nonmalignant etiologies that contribute to functional compromise.

Evaluating Treatment Tolerability Using the Toxicity Index With Patient-Reported Outcomes Data

CONTEXT

Summarizing longitudinal symptomatic adverse events during clinical trials is necessary for understanding treatment tolerability. The Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) provides insight for capturing treatment tolerability within trials. Tolerability summary measures, such as the maximum score, are often used to communicate the potential negative symptoms both in the medical literature and directly to patients. Commonly, the proportions of present and severe symptomatic adverse events are used and reported between treatment arms among adverse event types. The toxicity index is also a summary measure previously applied to clinician-reported CTCAE data.

OBJECTIVES

Apply the toxicity index to PRO-CTCAE data from the COMET-2 trial alongside the maximum score, then present and discuss considerations for using the toxicity index as a summary measure for communicating tolerability to patients and clinicians.

METHODS

Proportions of maximum PRO-CTCAE severity levels and median toxicity index were computed by arm using all trial data and adjusting for baseline symptoms.

RESULTS

Group-wise statistical differences were similar whether using severity level proportions or the toxicity index. The impact of adjusting for baseline symptoms was equivalently seen when comparing arms using severity rates or the toxicity index.

CONCLUSION

The toxicity index is a useful method when ranking patients from those with the least to most symptomatic adverse event burden. This study showed the toxicity index can be applied to PRO-CTCAE data. Though as a tolerability summary measure, further study is needed to provide a clear clinical or patient-facing interpretation of the toxicity index.

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.

Prospective Evaluation of Clinical Outcomes Using a Multiplex Liquid Biopsy Targeting Diverse Resistance Mechanisms in Metastatic Prostate Cancer

Nearly all men with prostate cancer treated with androgen receptor (AR) signaling inhibitors (ARSIs) develop resistance via diverse mechanisms including constitutive activation of the AR pathway, driven by AR genomic structural alterations, expression of AR splice variants (AR-Vs), or loss of AR dependence and lineage plasticity termed neuroendocrine prostate cancer. Understanding these de novo acquired ARSI resistance mechanisms is critical for optimizing therapy.

Tumor fraction-guided cell-free DNA profiling in metastatic solid tumor patients

BACKGROUND

Cell-free DNA (cfDNA) profiling is increasingly used to guide cancer care, yet mutations are not always identified. The ability to detect somatic mutations in plasma depends on both assay sensitivity and the fraction of circulating DNA in plasma that is tumor-derived (i.e., cfDNA tumor fraction). We hypothesized that cfDNA tumor fraction could inform the interpretation of negative cfDNA results and guide the choice of subsequent assays of greater genomic breadth or depth.

METHODS

Plasma samples collected from 118 metastatic cancer patients were analyzed with cf-IMPACT, a modified version of the FDA-authorized MSK-IMPACT tumor test that can detect genomic alterations in 410 cancer-associated genes. Shallow whole genome sequencing (sWGS) was also performed in the same samples to estimate cfDNA tumor fraction based on genome-wide copy number alterations using z-score statistics. Plasma samples with no somatic alterations detected by cf-IMPACT were triaged based on sWGS-estimated tumor fraction for analysis with either a less comprehensive but more sensitive assay (MSK-ACCESS) or broader whole exome sequencing (WES).

RESULTS

cfDNA profiling using cf-IMPACT identified somatic mutations in 55/76 (72%) patients for whom MSK-IMPACT tumor profiling data were available. A significantly higher concordance of mutational profiles and tumor mutational burden (TMB) was observed between plasma and tumor profiling for plasma samples with a high tumor fraction (z-score≥5). In the 42 patients from whom tumor data was not available, cf-IMPACT identified mutations in 16/42 (38%). In total, cf-IMPACT analysis of plasma revealed mutations in 71/118 (60%) patients, with clinically actionable alterations identified in 30 (25%), including therapeutic targets of FDA-approved drugs. Of the 47 samples without alterations detected and low tumor fraction (z-score<5), 29 had sufficient material to be re-analyzed using a less comprehensive but more sensitive assay, MSK-ACCESS, which revealed somatic mutations in 14/29 (48%). Conversely, 5 patients without alterations detected by cf-IMPACT and with high tumor fraction (z-score≥5) were analyzed by WES, which identified mutational signatures and alterations in potential oncogenic drivers not covered by the cf-IMPACT panel. Overall, we identified mutations in 90/118 (76%) patients in the entire cohort using the three complementary plasma profiling approaches.

CONCLUSIONS

cfDNA tumor fraction can inform the interpretation of negative cfDNA results and guide the selection of subsequent sequencing platforms that are most likely to identify clinically-relevant genomic alterations.

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]

Schlafen 11 (SLFN11), a putative predictive biomarker of platinum/PARPi response, is frequently detected on circulating tumor cells (CTCs) in advanced prostate cancer

e17039

Background: Schlafen 11 (SLFN11) is a DNA repair protein (DNA/RNA helicase homology) that is recruited to stressed replication forks and leads to cell death. Recent ph II trial data in Extensive Stage Small-Cell Lung Cancer (ES-SCLC) [Byers et al. JCO 2018 PMID: 29906251] and a retrospective analysis of Circulating Tumor Cells (CTCs) and tumor tissue in patients (Pts) with advanced prostate cancer [Conteduca et al. Mol Cancer Therapeutics 2020 PMID: 32127465] suggested that SLFN11 expression predicts sensitivity to DNA damage targeting agents. In both contexts, metastatic tumor biopsies may not provide adequate material for profiling. We assessed the frequency of SLFN11 expression in CTCs isolated from blood in men with progressing metastatic Castration Resistant Prostate Cancer (mCRPC) and related expression to Homologous Recombination Repair (HRR) alterations identified in metastatic tumor biopsies profiled by MSK-IMPACT. Methods: 95 patients with progressing mCRPC about to start a new systemic therapy who had undergone pre-treatment metastatic tumor profiling by MSK-IMPACT and a matched blood draw for CTC profiling were selected. Blood was sent overnight to Epic Sciences and processed onto glass pathology slides and bio-banked until analysis. Detected CTCs (cytokeratin (CK) positive and leukocyte (CD45) negative) were analyzed for SLFN11 protein expression by immunofluorescence and correlated to Homologous Recombination Repair (HRR) alterations in metastatic biopsy from the bone, lymph node, or visceral metastases (15 PROFOUND genes). A mean of 1.2 mL of blood was analyzed per patient. Results: CTCs with SLFN11 expression (DAPI+, CK+, CD45-, SLFN11+) were detected in 28.4% (27/95) of the patient sample analyzed. SLFN11 signal was found to overlap with the nuclear DAPI signal. Individual CTC expression of SLFN11 in a sample was heterogeneous and ranged from a minimum of 2.9% to 100%. Seven of 10 (70%) of patients with a BRCA1/2 or ATM alteration had a least one SLFN11 expressing CTC. In contrast, in patients with other HRR alterations, only 20% (1/5) had CTCs with SLFN11. Sequencing of single CTCs is ongoing. Conclusions: SLFN11 expression is detected with high frequency in CTCs in men with progressing mCRPC. In whom CTCs are detected, the majority of patients with BRCA1/2 or ATM altered tumors also had SLFN11 expressing CTCs. The results support the prospective evaluation of CTC SLFN11 expression as a predictive biomarker for PARPi or platinum agents.

Phase 3 Randomized Controlled Trial of Androgen Deprivation Therapy with or Without Docetaxel in High-risk Biochemically Recurrent Prostate Cancer After Surgery (TAX3503)

BACKGROUND

No standard of care exists for patients with high-risk biochemical recurrence (BCR) after prostatectomy.

OBJECTIVE

To evaluate whether addition of docetaxel to androgen deprivation therapy (ADT) improved progression-free survival (PFS) in high-risk BCR patients.

DESIGN, SETTING, AND PARTICIPANTS

TAX3503 was a multicenter phase 3 trial that randomized patients with high-risk BCR to ADT for 18 mo ± docetaxel (75 mg/m² q3w for ten cycles). Eligibility included prostate-specific antigen (PSA) ≥1.0 ng/ml after prostatectomy alone or after postoperative radiation therapy, PSA doubling time ≤9 mo, and absence of metastases on computed tomography and bone scintigraphy.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was PFS following testosterone recovery to noncastrate levels (testosterone >50 ng/dl). Secondary endpoints included time to testosterone recovery, overall survival (OS), quality of life, and safety.

RESULTS AND LIMITATIONS

Between September 2007 and May 2011, 413 patients were assigned to ADT ± docetaxel. In 2012, following completion of accrual and treatment, the sponsor withdrew support of the study, and in 2013, a registry was created to secure the primary endpoint. The final analysis included data from the original trial and registry. At a median follow-up of 33.6 mo, 260 patients demonstrated testosterone recovery, which occurred similarly between groups. ADT plus docetaxel trended toward a nonclinically meaningful improvement in PFS (median 26.2 vs 24.7 mo) for the testosterone-recovered population (218 events, hazard ratio [HR] 0.80, 95% confidence interval [CI] 0.61-1.04) and in OS for the intention-to-treat population (medians not reached, HR 0.51, 95% CI 0.23-1.10). Grade ≥3 adverse events occurred more frequently in the ADT plus docetaxel group (48.0% vs 10.8%).

CONCLUSIONS

TAX3503 did not demonstrate a meaningful benefit of adding docetaxel to ADT in patients with high-risk BCR. Testosterone recovery was unaffected by addition of docetaxel to ADT.

PATIENT SUMMARY

Addition of docetaxel to androgen deprivation therapy did not meaningfully improve outcomes for men with high-risk biochemically recurrent prostate cancer.

Development and validation of circulating tumour cell enumeration (Epic Sciences) as a prognostic biomarker in men with metastatic castration-resistant prostate cancer

PURPOSE

To evaluate the prognostic significance of circulating tumour cell (CTC) number determined on the Epic Sciences platform in men with metastatic castration-resistant prostate cancer (mCRPC) treated with an androgen receptor signalling inhibitor (ARSI).

PATIENTS AND METHODS

A pre-treatment blood sample was collected from men with progressing mCRPC starting either abiraterone or enzalutamide as a first-, second- or third-line systemic therapy at Memorial Sloan Kettering Cancer Center (Discovery cohort, N = 171) or as a first- or second-line therapy as part of the multicenter PROPHECY trial (NCT02269982) (Validation cohort, N = 107). The measured CTC number was then associated with overall survival (OS) in the Discovery cohort, and progression-free survival (PFS) and OS in the Validation cohort. CTC enumeration was also performed on a concurrently obtained blood sample using the CellSearch® Circulating Tumor Cell Kit.

RESULTS

In the MSKCC Discovery cohort, CTC count was a statistically significant prognostic factor of OS as a dichotomous (<3 CTCs/mL versus ≥ 3 CTCs/mL; hazard ratio [HR] = 1.8 [95% confidence interval {CI} 1.3-3.0]) and a continuous variable when adjusting for line of therapy, presence of visceral metastases, prostate-specific antigen, lactate dehydrogenase and alkaline phosphatase. The findings were validated in an independent datas et from PROPHECY (HR [95% CI] = 1.8 [1.1-3.0] for OS and 1.7 [1.1-2.9] for PFS). A strong correlation was also observed between CTC counts determined in matched samples on the CellSearch® and Epic platforms (r = 0.84).

CONCLUSION

The findings validate the prognostic significance of pretreatment CTC number determined on the Epic Sciences platform for predicting OS in men with progressing mCRPC starting an ARSI.

Initial Management of Noncastrate Advanced, Recurrent, or Metastatic Prostate Cancer: ASCO Guideline Update

PURPOSE

Update all preceding ASCO guidelines on initial hormonal management of noncastrate advanced, recurrent, or metastatic prostate cancer.

METHODS

The Expert Panel based recommendations on a systematic literature review. Recommendations were approved by the Expert Panel and the ASCO Clinical Practice Guidelines Committee.

RESULTS

Four clinical practice guidelines, one clinical practice guidelines endorsement, 19 systematic reviews with or without meta-analyses, 47 phase III randomized controlled trials, nine cohort studies, and two review papers informed the guideline update.

RECOMMENDATIONS

Docetaxel, abiraterone, enzalutamide, or apalutamide, each when administered with androgen deprivation therapy (ADT), represent four separate standards of care for noncastrate metastatic prostate cancer. Currently, the use of any of these agents in any particular combination or series cannot be recommended. ADT plus docetaxel, abiraterone, enzalutamide, or apalutamide should be offered to men with metastatic noncastrate prostate cancer, including those who received prior therapies, but have not yet progressed. The combination of ADT plus abiraterone and prednisolone should be considered for men with noncastrate locally advanced nonmetastatic prostate cancer who have undergone radiotherapy, rather than castration monotherapy. Immediate ADT may be offered to men who initially present with noncastrate locally advanced nonmetastatic disease who have not undergone previous local treatment and are unwilling or unable to undergo radiotherapy. Intermittent ADT may be offered to men with high-risk biochemically recurrent nonmetastatic prostate cancer. Active surveillance may be offered to men with low-risk biochemically recurrent nonmetastatic prostate cancer. The panel does not support use of either micronized abiraterone acetate or the 250 mg dose of abiraterone with a low-fat breakfast in the noncastrate setting at this time.Additional information is available at www.asco.org/genitourinary-cancer-guidelines.

Circulating Tumor Cell Chromosomal Instability and Neuroendocrine Phenotype by Immunomorphology and Poor Outcomes in Men with mCRPC Treated with Abiraterone or Enzalutamide

PURPOSE

While the detection of AR-V7 in circulating tumor cells (CTC) is associated with resistance to abiraterone or enzalutamide in men with metastatic castration-resistant prostate cancer (mCRPC), it only accounts for a minority of this resistance. Neuroendocrine (NE) differentiation or chromosomal instability (CIN) may be additional mechanisms that mediate resistance.

EXPERIMENTAL DESIGN

PROPHECY was a multicenter prospective study of men with high-risk mCRPC starting abiraterone or enzalutamide. A secondary objective was to assess Epic CTC CIN and NE phenotypes before abiraterone or enzalutamide and at progression. The proportional hazards (PH) model was used to investigate the prognostic importance of CIN and NE in predicting progression-free survival and overall survival (OS) adjusting for CTC number (CellSearch), AR-V7, prior therapy, and clinical risk score. The PH model was utilized to validate this association of NE with OS in an external dataset of patients treated similarly at Memorial Sloan Kettering Cancer Center (MSKCC; New York, NY).

RESULTS

We enrolled 118 men with mCRPC starting on abiraterone or enzalutamide; 107 were evaluable on the Epic platform. Of these, 36.4% and 8.4% were CIN positive and NE positive, respectively. CIN and NE were independently associated with worse OS [HR, 2.2; 95% confidence interval (CI), 1.2-4.0 and HR 3.8; 95% CI, 1.2-12.3, respectively] when treated with abiraterone/enzalutamide. The prognostic significance of NE positivity for worse OS was confirmed in the MSKCC dataset (n = 173; HR, 5.7; 95% CI, 2.6-12.7).

CONCLUSIONS

A high CIN and NE CTC phenotype is independently associated with worse survival in men with mCRPC treated with abiraterone/enzalutamide, warranting further prospective controlled predictive studies to inform treatment decisions.

Development and validation of circulating tumor cell (Epic Sciences) enumeration as a prognostic biomarker in men with metastatic castration-resistant prostate cancer

157

Background: We evaluated the prognostic significance of circulating tumor cell (CTC) number as determined on the Epic Sciences platform in men with metastatic castration resistant prostate cancer (mCRPC) treated with an androgen receptor signaling inhibitor (ARSI). Methods: A pre-treatment blood sample was collected from men with progressing mCRPC starting either abiraterone or enzalutamide as a 1st, 2nd or 3rd line systemic therapy at Memorial Sloan Kettering Cancer Center (Discovery cohort, N=175) or as a 1st and 2nd line therapy as part of the multi-center PROPHECY trial (NCT02269982) (Validation cohort, N=107). Enumeration was performed on the Epic Sciences platform and associated with overall survival (OS) in the Discovery cohort, and progression-free survival (PFS) and OS in the Validation cohort. Matched blood samples from the Validation cohort were to CTC counts measured on the CellSearch Circulating Tumor Cell kit. Results: In the MSKCC Discovery cohort, CTC count was a statistically significant prognostic factor of OS as a dichotomous (< 3 CTCs/mL versus ≥ 3 CTCs/mL; HR = 1.8, (1.3-3.0, 95% CI)) and as a continuous variable when adjusting for line of therapy, presence of visceral metastases, PSA, lactate-dehydrogenase, and alkaline-phosphatase. The findings were validated in an independent dataset (PROPHECY trial) - (HR (95% CI) = 1.8, (1.1-3.0) for OS and 1.7 (1.1-2.9), for PFS). A strong correlation was observed between CTC counts determined in matched samples on the CellSearch and Epic platforms (r = 0.84). Conclusions: The findings validate the prognostic significance of pretreatment CTC number determined on the Epic Sciences platform for predicting OS in men with progressing mCRPC starting an ARSI.

PSA-Targeted Alpha-, Beta-, and Positron-Emitting Immunotheranostics in Murine Prostate Cancer Models and Nonhuman Primates

PURPOSE

Most patients with prostate cancer treated with androgen receptor (AR) signaling inhibitors develop therapeutic resistance due to restoration of AR functionality. Thus, there is a critical need for novel treatment approaches. Here we investigate the theranostic potential of hu5A10, a humanized mAb specifically targeting free PSA (KLK3).

EXPERIMENTAL DESIGN

LNCaP-AR (LNCaP with overexpression of wildtype AR) xenografts (NSG mice) and KLK3_Hi-Myc transgenic mice were imaged with ⁸⁹Zr- or treated with ⁹⁰Y- or ²²⁵Ac-labeled hu5A10; biodistribution and subcellular localization were analyzed by gamma counting, PET, autoradiography, and microscopy. Therapeutic efficacy of [²²⁵Ac]hu5A10 and [⁹⁰Y]hu5A10 in LNCaP-AR tumors was assessed by tumor volume measurements, time to nadir (TTN), time to progression (TTP), and survival. Pharmacokinetics of [⁸⁹Zr]hu5A10 in nonhuman primates (NHP) were determined using PET.

RESULTS

Biodistribution of radiolabeled hu5A10 constructs was comparable in different mouse models. Specific tumor uptake increased over time and correlated with PSA expression. Treatment with [⁹⁰Y]/[²²⁵Ac]hu5A10 effectively reduced tumor burden and prolonged survival (P ≤ 0.0054). Effects of [⁹⁰Y]hu5A10 were more immediate than [²²⁵Ac]hu5A10 (TTN, P < 0.0001) but less sustained (TTP, P < 0.0001). Complete responses were observed in 7 of 18 [²²⁵Ac]hu5A10 and 1 of 9 mice [⁹⁰Y]hu5A10. Pharmacokinetics of [⁸⁹Zr]hu5A10 were consistent between NHPs and comparable with those in mice. [⁸⁹Zr]hu5A10-PET visualized the NHP-prostate over the 2-week observation period.

CONCLUSIONS

We present a complete preclinical evaluation of radiolabeled hu5A10 in mouse prostate cancer models and NHPs, and establish hu5A10 as a new theranostic agent that allows highly specific and effective downstream targeting of AR in PSA-expressing tissue. Our data support the clinical translation of radiolabeled hu5A10 for treating prostate cancer.

Quantification of Metastatic Prostate Cancer Whole-Body Tumor Burden with 18F-FDG PET Parameters and Associations with Overall Survival After First-Line Abiraterone or Enzalutamide: A Single-Center Retrospective Cohort Study

New biomarkers for metastatic prostate cancer are needed. The aim of this study was to evaluate the prognostic value of ¹⁸F-FDG PET whole-body tumor burden parameters in patients with metastatic prostate cancer who received first-line abiraterone or enzalutamide therapy. Methods: This was a retrospective study of patients with metastatic castration-sensitive prostate cancer (mCSPC, n = 25) and metastatic castration-resistant prostate cancer (mCRPC, n = 71) who underwent ¹⁸F-FDG PET/CT within 90 d before first-line treatment with abiraterone or enzalutamide at a tertiary-care academic cancer center. Whole-body tumor burden on PET/CT was quantified as metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and correlated with overall survival (OS) probabilities using Kaplan-Meier curves and Cox models. Results: The median follow-up in survivors was 56.3 mo (interquartile range, 37.7-66.8 mo); the median OSs for patients with mCRPC and mCSPC were 27.8 and 76.1 mo, respectively (P < 0.001). On univariate analysis, the OS probability of mCRPC patients was significantly associated with plasma levels of alkaline phosphatase (hazard ratio [HR], 1.90; P < 0.001), plasma levels of lactate dehydrogenase (HR, 1.01; P < 0.001), hemoglobin levels (HR, 0.80; P = 0.013), whole-body SUV_max (HR, 1.14; P < 0.001), the number of ¹⁸F-FDG-avid metastases (HR, 1.08; P < 0.001), whole-body metabolic tumor volume (HR, 1.86; P < 0.001), and TLG (HR, 1.84; P < 0.001). On multivariable analysis with stepwise variable selection, hemoglobin levels (HR, 0.81; P = 0.013) and whole-body TLG (HR, 1.88; P < 0.001) were independently associated with OS. In mCSPC patients, no significant association was observed between these variables and OS. Conclusion: In patients with mCRPC receiving first-line treatment with abiraterone or enzalutamide, ¹⁸F-FDG PET WB TLG is independently associated with OS and might be used as a quantitative prognostic imaging biomarker.

Prostate Cancer Foundation Hormone-Sensitive Prostate Cancer Biomarker Working Group Meeting Summary

Androgen deprivation therapy remains the backbone therapy for the treatment of metastatic hormone-sensitive prostate cancer (mHSPC). In recent years, several treatments, including docetaxel, abiraterone + prednisone, enzalutamide, and apalutamide, have each been shown to demonstrate survival benefit when used upfront along with androgen deprivation therapy. However, treatment selection for an individual patient remains a challenge. There is no high level clinical evidence for treatment selection among these choices based on biological drivers of clinical disease. In August 2020, the Prostate Cancer Foundation convened a working group to meet and discuss biomarkers for hormone-sensitive prostate cancer, the proceedings of which are summarized here. This meeting covered the state of clinical and biological evidence for systemic therapies in the mHSPC space, with emphasis on charting a course for the generation, interrogation, and clinical implementation of biomarkers for treatment selection.

Final Analysis of the Ipilimumab Versus Placebo Following Radiotherapy Phase III Trial in Postdocetaxel Metastatic Castration-resistant Prostate Cancer Identifies an Excess of Long-term Survivors

BACKGROUND

The phase 3 trial CA184-043 evaluated radiotherapy to bone metastases followed by Ipilimumab or placebo in men with metastatic castrate-resistant prostate cancer (mCRPC) who had received docetaxel previously. In a prior analysis, the trial's primary endpoint (overall survival [OS]) was not improved significantly.

OBJECTIVE

To report the final analysis of OS.

DESIGN, SETTING, AND PARTICIPANTS

A total of 799 patients were randomized to receive a single dose of radiotherapy to one or more bone metastases followed by either Ipilimumab (n = 399) or placebo (n = 400).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

OS was analyzed in the intention-to-treat population. Prespecified and exploratory subset analyses based on Kaplan-Meier/Cox methodology were performed.

RESULTS AND LIMITATIONS

During an additional follow-up of approximately 2.4 yr since the primary analysis, 721/799 patients have died. Survival analysis showed crossing of the curves at 7-8 mo, followed by persistent separation of the curves beyond that point, favoring the ipilimumab arm. Given the lack of proportional hazards, a piecewise hazard model showed that the hazard ratio (HR) changed over time: the HR was 1.49 (95% confidence interval 1.12, 1.99) for 0-5 mo, 0.66 (0.51, 0.86) for 5-12 mo, and 0.66 (0.52, 0.84) beyond 12 mo. OS rates were higher in the ipilimumab versus placebo arms at 2 yr (25.2% vs 16.6%), 3 yr (15.3% vs 7.9%), 4 yr (10.1% vs 3.3%), and 5 yr (7.9% vs. 2.7%). Disease progression was the most frequent cause of death in both arms. In seven patients (1.8%) in the ipilimumab arm and one (0.3%) in the placebo arm, the primary cause of death was reported as study drug toxicity. No long-term safety signals were identified.

CONCLUSIONS

In this preplanned long-term analysis, OS favored ipilimumab plus radiotherapy versus placebo plus radiotherapy for patients with postdocetaxel mCRPC. OS rates at 3, 4, and 5 yr were approximately two to three times higher in the ipilimumab arm.

PATIENT SUMMARY

After longer follow-up, survival favored the group of men who received ipilimumab, with overall survival rates being two to three times higher at 3 yr and beyond.

Pan-cancer Analysis of CDK12 Alterations Identifies a Subset of Prostate Cancers with Distinct Genomic and Clinical Characteristics

BACKGROUND

CDK12 genomic alterations occur in several tumor types, but little is known about their oncogenic role and clinical significance.

OBJECTIVE

To describe the landscape of CDK12 alterations across solid cancers and the clinical features of CDK12-altered prostate cancer.

DESIGN, SETTING, AND PARTICIPANTS

A single-center retrospective study of 26743 patients across 25 solid tumor types who underwent tumor sequencing was performed. Clinicopathologic features and outcomes were assessed in prostate cancer.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

CDK12 alterations and their association with genomic characteristics are described. For prostate cancer patients, overall survival and time to castration resistance were assessed using univariable and multivariable Cox regression analysis.

RESULTS AND LIMITATIONS

CDK12 alterations were identified in 404/26743 patients (1.5%) overall, but were most frequent in prostate (100/1875, 5.3%) and ovarian cancer (43/1034, 4.2%), in which they were associated with a high prevalence of truncating variants and biallelic inactivation. CDK12 alterations defined a genomic subtype of prostate cancer with a unique copy-number alteration profile and involvement of distinct oncogenic pathway alterations, including cell-cycle pathway genes. CDK12-altered prostate cancer was associated with somewhat more aggressive clinical features and shorter overall survival (median 64.4 vs 74.9 mo; p=0.032) independent of standard clinical factors and tumor copy-number alteration burden (adjusted hazard ratio 1.80, 95% confidence interval 1.12-2.89; p=0.024). The study is limited by its retrospective nature.

CONCLUSIONS

CDK12 alteration is a rare event across solid cancers but defines a clinically distinct molecular subtype of prostate cancer associated with unique genomic alterations and slightly more aggressive clinical features.

PATIENT SUMMARY

CDK12 gene alterations occur rarely across tumor types, but more frequently in prostate cancer, where they are associated with genomic instability, cell-cycle pathway gene alterations, and somewhat worse clinical outcomes, warranting further investigation of therapeutic targeting of this disease subset.

Impact of clinical versus radiographic progression on clinical outcomes in metastatic castration-resistant prostate cancer

OBJECTIVES

Unequivocal clinical progression (UCP)-a worsening of clinical status with or without radiographic progression (RAD)-represents a distinct mode of disease progression in metastatic prostate cancer. We evaluated the prevalence, risk factors and the impact of UCP on survival outcomes.

METHODS

A post-hoc analysis of the COU-AA-302, a randomised phase 3 study of abiraterone plus prednisone (AAP) versus prednisone was performed. Baseline characteristics were summarised. Cox proportional-hazards model and Kaplan-Meier method were used for survival and time to event analyses, respectively. Iterative multiple imputation method was used for correlation between clinicoradiographic progression-free survival (crPFS) and overall survival (OS).

RESULTS

Of 736 patients with disease progression, 280 (38%) had UCP-only and 124 (17%) had UCP plus RAD. Prognostic index model high-risk group was associated with increased likelihood of UCP (p<0.0001). Median OS was 25.7 months in UCP-only and 33.0 months for RAD-only (HR 1.39; 95% CI 1.16 to 1.66; p=0.0003). UCP adversely impacted OS in both treatment groups. Lowest OS was seen in patients with prostate specific antigen (PSA)-non-response plus UCP-only progression (median OS 22.6 months (95% CI 20.7 to 24.4)). Including UCP events lowered estimates of treatment benefit-median crPFS was 13.3 months (95% CI 11.1 to 13.8) versus median rPFS of 16.5 months (95% CI 13.8 to 16.8) in AAP group. Finally, crPFS showed high correlation with OS (r=0.67; 95% CI 0.63 to 0.71).

CONCLUSIONS

UCP is a common and clinically relevant phenomenon in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with AAP or prednisone. UCP is prognostic and associated with inferior OS and post-progression survival. A combination of PSA-non-response and UCP identifies patients with poorest survival. When included in PFS analysis, UCP diminishes estimates of treatment benefit. Continued study of UCP in mCRPC is warranted.