Association of PARP inhibitor treatment on the prevalence and progression of clonal hematopoiesis in patients with advanced prostate cancer

BACKGROUND

Poly ADP-ribose polymerase (PARP) inhibitors are approved for the treatment of some men with advanced prostate cancer. Rare but serious side effects include myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). The impact of PARP inhibitors on clonal hematopoiesis (CH), a potential precursor lesion associated with MDS and AML, is incompletely understood in prostate cancer. We hypothesized that PARP inhibitors would increase CH prevalence and abundance.

METHODS

We prospectively enrolled participants with advanced prostate cancer treated with PARP inhibitors. The presence of CH was assessed from leukocytes using an ultra-deep error-corrected dual unique molecular identifiers sequencing method targeting 49 genes most commonly mutated in CH and myeloid malignancies. Variant allele frequencies (VAF) of ≥0.5% were considered clinically significant. Blood samples were collected before and after PARP inhibitor treatment.

RESULTS

Ten men were enrolled; mean age of 67 years. Six patients had Gleason 7 disease, and four had Gleason ≥8 disease at diagnosis. Nine had localized disease at diagnosis, and eight had prior treatment with radiation. The mean time between pre- and post-treatment blood samples was 11 months (range 2.6-31 months). Six patients (60%) had CH identified prior to PARP inhibitor treatment, three with multiple clones. Of 11 CH clones identified in follow-up, 5 (45%) appeared or increased after treatment. DNMT3A, TET2, and PPM1D were the most common CH alterations observed. The largest post-treatment increase involved the PPM1D gene.

CONCLUSION

CH alterations are frequently found after treatment with PARP inhibitors in patients with prostate cancer and this may be one mechanism by which PARP inhibitors lead to increased risk of MDS/AML.

Clinical management and outcomes of HIV-positive patients newly diagnosed with prostate cancer: a single institution experience

INTRODUCTION

10-year outcomes in patients living with HIV who are diagnosed with prostate cancer are unknown.

METHODS

52 patients living with HIV were diagnosed with prostate cancer. Disease-free survival stratified by clinical, pathologic, and HIV characteristics were examined.

RESULTS

No difference in disease-free survival was observed based on prostate cancer treatment modality, CD4 count, or HIV viral load.

CONCLUSIONS

Prostate cancer outcomes in patients living with HIV are favorable irrespective of treatment modality.

Bipolar androgen therapy plus nivolumab for patients with metastatic castration-resistant prostate cancer: the COMBAT phase II trial

Cyclic high-dose testosterone administration, known as bipolar androgen therapy (BAT), is a treatment strategy for patients with metastatic castration-resistant prostate cancer (mCRPC). Here, we report the results of a multicenter, single arm Phase 2 study (NCT03554317) enrolling 45 patients with heavily pretreated mCRPC who received BAT (testosterone cypionate, 400 mg intramuscularly every 28 days) with the addition of nivolumab (480 mg intravenously every 28 days) following three cycles of BAT monotherapy. The primary endpoint of a confirmed PSA50 response rate was met and estimated at 40% (N = 18/45, 95% CI: 25.7-55.7%, P = 0.02 one-sided against the 25% null hypothesis). Sixteen of the PSA50 responses were achieved before the addition of nivolumab. Secondary endpoints included objective response rate (ORR), median PSA progression-free survival, radiographic progression-free survival (rPFS), overall survival (OS), and safety/tolerability. The ORR was 24% (N = 10/42). Three of the objective responses occurred following the addition of nivolumab. After a median follow-up of 17.9 months, the median rPFS was 5.6 (95% CI: 5.4-6.8) months, and median OS was 24.4 (95% CI: 17.6-31.1) months. BAT/nivolumab was well tolerated, resulting in only five (11%) drug related, grade-3 adverse events. In a predefined exploratory analysis, clinical response rates correlated with increased baseline levels of intratumoral PD-1 + T cells. In paired metastatic tumor biopsies, BAT induced pro-inflammatory gene expression changes that were restricted to patients achieving a clinical response. These data suggest that BAT may augment antitumor immune responses that are further potentiated by immune checkpoint blockade.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type-specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by 2 orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Vascular Expression of Prostate-specific Membrane Antigen (PSMA) in MiTF Family Translocation Renal Cell Carcinoma and Related Neoplasms

Multiple studies have demonstrated prostate-specific membrane antigen (PSMA) expression in the neo-vasculature of non-prostate tumors including clear cell renal cell carcinoma (ccRCC). However, PSMA expression in rare renal tumors including MiTF family translocation renal cell carcinoma has not been previously characterized. We examined PSMA expression by immunohistochemistry in a series of MiTF family translocation renal cell carcinomas as well as in several genetically related tumors including alveolar soft part sarcoma and PEComas with TFE3 rearrangements. PSMA expression was also studied in several cases of ccRCC and papillary RCC. Overall, PSMA immunohistochemistry was performed in 61 samples from 58 patients. Vascular PSMA expression was seen with the highest frequency in ccRCC [88% (14/16)] (38% focal, 50% diffuse). Translocation RCC (tRCC) demonstrated the second highest frequency of PSMA expression [71% (22/28)] (57% focal, 14% diffuse), followed by alveolar soft part sarcoma [50% (4/8)] (38% focal, 12% diffuse). No PSMA expression was seen in PEComas with TFE3 rearrangement (0/3) or papillary RCC (0/6). PSMA expression was only present in tumor-associated neo-vasculature. A patient with oligometastatic tRCC underwent 68 Ga-PSMA-11 PET imaging which detected multiple putative metastatic lesions not detected on conventional computed tomography imaging performed 2 weeks prior, supporting the potential utility of PSMA imaging in tRCC. These findings have potential implications for the utility of PSMA guided diagnostic and therapeutic agents in both common and uncommon renal cell carcinoma subtypes as well as genetically related mesenchymal neoplasms.

Test-retest repeatability of organ uptake on PSMA-targeted 18 F-DCFPyL PET/CT in patients with prostate cancer

OBJECTIVES

We evaluated ¹⁸ F-DCFPyL test-retest repeatability of uptake in normal organs.

METHODS

Twenty-two prostate cancer (PC) patients underwent two ¹⁸ F-DCFPyL PET scans within 7 days within a prospective clinical trial (NCT03793543). In both PET scans, uptake in normal organs (kidneys, spleen, liver, and salivary and lacrimal glands) was quantified. Repeatability was determined by using within-subject coefficient of variation (wCOV), with lower values indicating improved repeatability.

RESULTS

For SUV_mean , repeatability was high for kidneys, spleen, liver, and parotid glands (wCOV, range: 9.0%-14.3%) and lower for lacrimal (23.9%) and submandibular glands (12.4%). For SUV_max , however, the lacrimal (14.4%) and submandibular glands (6.9%) achieved higher repeatability, while for large organs (kidneys, liver, spleen, and parotid glands), repeatability was low (range: 14.1%-45.2%).

CONCLUSION

We found acceptable repeatability of uptake on ¹⁸ F-DCFPyL PET for normal organs, in particular for SUV_mean in the liver or parotid glands. This may have implications for both PSMA-targeted imaging and treatment, as patient selection for radioligand therapy and standardized frameworks for scan interpretation (PROMISE, E-PSMA) rely on uptake in those reference organs.

Safety and clinical efficacy of immune checkpoint inhibition and stereotactic body radiotherapy in patients with spine metastasis

OBJECTIVE

Immunotherapy, particularly immune checkpoint inhibitors (ICIs), has revolutionized the treatment of patients with many tumor histologies. Simultaneously, stereotactic body radiotherapy (SBRT) provides excellent local control (LC) and plays an important role in the management of spine metastasis. Promising preclinical work suggests the potential therapeutic benefit of combining SBRT with ICI therapy, but the safety profile of combined therapy is unclear. This study aimed to evaluate the toxicity profile associated with ICI in patients receiving SBRT and, secondarily, whether ICI administration sequence with respect to SBRT affects LC or overall survival (OS) outcomes.

METHODS

The authors retrospectively reviewed patients with spine metastasis treated with SBRT at an academic center. Patients who received ICI at any point during their disease course were compared to those with the same primary tumor types who did not receive ICI by using Cox proportional hazards analyses. Primary outcomes were long-term sequelae, including radiation-induced spinal cord myelopathy, esophageal stricture, and bowel obstruction. Secondarily, models were created to evaluate OS and LC in the cohort.

RESULTS

Two hundred forty patients who received SBRT to 299 spine metastases were included in this study. The most common primary tumor types were non-small cell lung cancer (n = 59 [24.6%]) and renal cell carcinoma (n = 55 [22.9%]). One hundred eight patients received at least 1 dose of ICI, with the most common regimen being single-agent anti-PD-1 (n = 80 [74.1%]), followed by combination CTLA-4/PD-1 inhibitors (n = 19 [17.6%]). Three patients experienced long-term radiation-induced sequelae: 2 had esophageal stricture and 1 had bowel obstruction. No patients developed radiation-induced myelopathy. There was no association between receipt of ICI and development of any of these adverse events (p > 0.9). Similarly, ICI was not significantly associated with either LC (p = 0.3) or OS (p = 0.6). In the entire cohort, patients who received ICI prior to beginning SBRT had worse median survival, but ICI sequence with respect to SBRT was not significantly prognostic of either LC (p > 0.3) or OS (p > 0.07); instead, baseline performance status was most predictive of OS (HR 1.38, 95% CI 1.07-1.78, p = 0.012).

CONCLUSIONS

Treatment regimens that combine ICIs before, concurrent with, and after SBRT for spine metastases are safe, with minimal risk for increased rates of long-term toxicity.

Lack of repeatability of radiomic features derived from PET scans: Results from a 18 F-DCFPyL test-retest cohort

OBJECTIVES

PET-based radiomic metrics are increasingly utilized as predictive image biomarkers. However, the repeatability of radiomic features on PET has not been assessed in a test-retest setting. The prostate-specific membrane antigen-targeted compound ¹⁸ F-DCFPyL is a high-affinity, high-contrast PET agent that we utilized in a test-retest cohort of men with metastatic prostate cancer (PC).

METHODS

Data of 21 patients enrolled in a prospective clinical trial with histologically proven PC underwent two ¹⁸ F-DCFPyL PET scans within 7 days, using identical acquisition and reconstruction parameters. Sites of disease were segmented and a set of 29 different radiomic parameters were assessed on both scans. We determined repeatability of quantification by using Pearson's correlations, within-subject coefficient of variation (wCOV), and Bland-Altman analysis.

RESULTS

In total, 230 lesions (177 bone, 38 lymph nodes, 15 others) were assessed on both scans. For all investigated radiomic features, a broad range of inter-scan correlation was found (r, 0.07-0.95), with acceptable reproducibility for entropy and homogeneity (wCOV, 16.0% and 12.7%, respectively). On Bland-Altman analysis, no systematic increase or decrease between the scans was observed for either parameter (±1.96 SD: 1.07/-1.30, 0.23/-0.18, respectively). The remaining 27 tested radiomic metrics, however, achieved unacceptable high wCOV (≥21.7%).

CONCLUSION

Many common radiomic features derived from a test-retest PET study had poor repeatability. Only Entropy and homogeneity achieved good repeatability, supporting the notion that those image biomarkers may be incorporated in future clinical trials. Those radiomic features based on high frequency aspects of images appear to lack the repeatability on PET to justify further study.

Bipolar Androgen Therapy Followed by Androgen Receptor Inhibition as Sequential Therapy for Prostate Cancer

Inhibition of androgen receptor (AR) signaling has been the mainstay of treatment of advanced prostate cancer (PCa) for the past 80 years. Combination and sequential AR-inhibiting therapies are highly effective palliative therapy, but they are not curative. All patients eventually develop resistance to primary castrating therapy [ie, castration-resistant PCa (CRPC)]. At this point, they are treated with subsequent lines of secondary AR inhibitory therapies. However, resistance to these agents also develops and patients progress to a state we have termed complete androgen inhibition-resistant PCa. This phase of the disease is associated with poor prognosis. At this point, treatment shifts to non-hormonal cytotoxic therapies (eg, chemotherapy and radiopharmaceuticals). However, the majority of PCas remain addicted to signaling through AR throughout the course of the disease. Resistant PCa cells adaptively upregulate AR activity, despite castration and AR inhibitors, via mechanisms such as AR overexpression, gene amplification, mutation, and expression of ligand-independent variants to permit sustained liganded and non-liganded AR signaling. Studies dating back nearly 30 years indicate that high expression of AR induced by prolonged castration becomes a vulnerability of CRPC cells in vitro and in mouse xenografts to supraphysiologic androgen (SPA), which induces cell death and growth arrest in this context. Based on these studies, we developed a counterintuitive treatment called bipolar androgen therapy (BAT) for patients with CRPC, in which SPA is administered intermittently to result in cycling of serum testosterone from the polar extremes of supraphysiologic to near-castrate levels. This rapid cycling is intended to disrupt the adaptive of AR regulation associated with chronic exposure to high or low levels of testosterone, while simultaneously targeting the spectrum of AR expression present in heterogeneous CRPC tumors. We have now tested BAT in >250 patients with CRPC. Here we present a review of these clinical studies, which have demonstrated collectively that BAT can be safely given to men with CRPC, improves quality of life, and produces therapeutic responses in ~30% of patients. As expected, resistance to BAT is associated with adaptive downregulation of AR expression. Intriguingly, this downregulation is associated with restoration of sensitivity to subsequent AR inhibitor therapies.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Role of bromodomain and extraterminal (BET) proteins in prostate cancer

INTRODUCTION

The bromodomain and extraterminal (BET) family of proteins are epigenetic readers of acetylated histones and are critical activators of oncogenic networks across many cancers. Therapeutic targeting of BET proteins has been an attractive area of clinical development for metastatic castration-resistant prostate cancer. In recent years, many structurally diverse BET inhibitors have been discovered and tested. Preclinical studies have demonstrated significant antiproliferative activity of BET inhibitors against prostate cancer. However, their clinical success as monotherapies has been limited by treatment-associated toxicities, primary and acquired drug resistance, and a lack of predictive biomarkers of benefit.

AREAS COVERED

This review provides an overview of advancements in BET inhibitor design, preclinical research, and conclusions from clinical trials in prostate cancer. We speculate on incorporating BET inhibitors into combination regimens with other agents to improve the therapeutic index of BET inhibition in treating prostate cancer.

EXPERT OPINION

The therapeutic potential of BET inhibitors for prostate cancer has been demonstrated in preclinical studies. However, further research is needed to identify biomarkers that can predict sensitivity to BET inhibitors and to develop novel, highly selective inhibitors to reduce toxicities. Finally, BET inhibitors are likely to hold the most clinical potential in combination with other agents.

Androgen receptor activity in prostate cancer dictates efficacy of bipolar androgen therapy through MYC

Testosterone is the canonical growth factor of prostate cancer but can paradoxically suppress its growth when present at supraphysiological levels. We have previously demonstrated that the cyclical administration of supraphysiological androgen (SPA), termed bipolar androgen therapy (BAT), can result in tumor regression and clinical benefit for patients with castration-resistant prostate cancer. However, predictors and mechanisms of response and resistance have been ill defined. Here, we show that growth inhibition of prostate cancer models by SPA required high androgen receptor (AR) activity and were driven in part by downregulation of MYC. Using matched sequential patient biopsies, we show that high pretreatment AR activity predicted downregulation of MYC, improved clinical response, and prolonged progression-free and overall survival for patients on BAT. BAT induced strong downregulation of AR in all patients, which is shown to be a primary mechanism of acquired resistance to SPA. Acquired resistance was overcome by alternating SPA with the AR inhibitor enzalutamide, which induced adaptive upregulation of AR and resensitized prostate cancer to SPA. This work identifies high AR activity as a predictive biomarker of response to BAT and supports a treatment paradigm for prostate cancer involving alternating between AR inhibition and activation.

The shifting treatment paradigm of metastatic renal cell carcinoma

The treatment landscape of renal cell carcinoma is rapidly evolving, especially with the introduction and approval of immune checkpoint inhibitor combination therapies. Clinical trial data show substantial improvements in patient outcomes, and now results in the real-world setting support the use of these combinations.

A Phase Ib/II Study of Sabizabulin, a Novel Oral Cytoskeleton Disruptor, in Men with Metastatic Castration-resistant Prostate Cancer with Progression on an Androgen Receptor-targeting Agent

PURPOSE

Sabizabulin, an oral cytoskeleton disruptor, was tested in a phase Ib/II clinical study in men with metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

The phase Ib portion utilized a 3+3 design with escalating daily oral doses of 4.5-81 mg and increasing schedule in 39 patients with mCRPC treated with one or more androgen receptor-targeting agents. Prior taxane chemotherapy was allowed. The phase II portion tested a daily dose of 63 mg in 41 patients with no prior chemotherapy. Efficacy was assessed using PCWG3 and RECIST 1.1 criteria.

RESULTS

The MTD was not defined in the phase Ib and the recommended phase II dose was set at 63 mg/day. The most common adverse events (>10% frequency) at the 63 mg oral daily dosing (combined phase Ib/II data) were predominantly grade 1-2 events. Grade ≥3 events included diarrhea (7.4%), fatigue (5.6%), and alanine aminotransferase/aspartate aminotransferase elevations (5.6% and 3.7%, respectively). Neurotoxicity and neutropenia were not observed. Preliminary efficacy data in patients treated with ≥1 continuous cycle of 63 mg or higher included objective response rate in 6 of 29 (20.7%) patients with measurable disease (1 complete, 5 partial) and 14 of 48 (29.2%) patients had PSA declines. The Kaplan-Meier median radiographic progression-free survival was estimated to be 11.4 months (n = 55). Durable responses lasting >2.75 years were observed.

CONCLUSIONS

This clinical trial demonstrated that chronic oral daily dosing of sabizabulin has a favorable safety profile with preliminary antitumor activity. These data support the ongoing phase III VERACITY trial of sabizabulin in men with mCRPC.

Clinical Efficacy of Bipolar Androgen Therapy in Men with Metastatic Castration-Resistant Prostate Cancer and Combined Tumor-Suppressor Loss

Bipolar androgen therapy (BAT) relies on oscillating levels of serum testosterone as a way to treat patients with metastatic castration-resistant prostate cancer (mCRPC). Aggressive-variant prostate cancers typically require combination chemotherapy and are frequently associated with loss-of-function mutations in tumor suppressor genes. Here we report clinical outcomes after BAT among patients with mCRPC harboring pathogenic alterations in at least two of three genes: TP53, PTEN, and RB1. In this setting, BAT induced a meaningful PSA50 response rate, progression-free survival and overall survival, particularly in patients without prior chemotherapy.

Patient summary

Bipolar androgen therapy, in which drugs are used to raise testosterone levels and then allow them to decrease again in a cycle, may be a safe and effective treatment for prostate cancer that is resistant to testosterone suppression and has mutations in tumor suppressor genes. A randomized study comparing this approach to chemotherapy is needed to confirm the findings.

Bipolar androgen therapy (BAT): A patient's guide

Bipolar androgen therapy (BAT) is a new treatment concept for men whose prostate cancer has become resistant to standard hormone-blocking therapy. Over the past decade, we have performed a series of clinical studies testing BAT in asymptomatic men with castration-resistant prostate cancer. The key findings from these clinical studies are that BAT (a) can be safely administered to asymptomatic patients with metastatic castrate-resistant prostate cancer; (b) does not produce symptomatic disease progression; (c) produces sustained prostate-specific antigen and objective responses in 30%-40% of patients; and (d) can resensitize and prolong response to subsequent antiandrogen therapy. The concept of BAT has generated significant interest from men with prostate cancer, their families, and their physicians. Here we provide a "Patient's Guide" that answers questions about BAT in a form that is accessible to patients, their families, and physicians. Our goal is to provide information to help patients make the most informed decisions they can regarding their prostate cancer treatment.

Molecular and Clinical Characterization of Patients With Metastatic Castration Resistant Prostate Cancer Achieving Deep Responses to Bipolar Androgen Therapy

BACKGROUND

Bipolar androgen therapy (BAT) is an emerging treatment strategy for men with metastatic castration resistant prostate cancer (mCRPC) whereby serum testosterone is cycled from supraphysiologic to near-castrate levels each month. BAT has been shown to induce clinical responses in a significant proportion of patients, some of which are extreme. We explored the clinical and molecular characteristics of patients with mCRPC who achieved deep responses to BAT.

METHODS

We conducted a retrospective analysis of patients with mCRPC treated with BAT at Johns Hopkins. We identified 22 of 114 (19%) patients with mCRPC who achieved ≥70% PSA reductions upon treatment with BAT. All patients were treated using 400 mg testosterone cypionate intramuscularly every 28 days, together with continuous LHRH agonist therapy. Clinical-grade DNA sequencing was obtained using commercially available assays.

RESULTS

Somatic next-generation sequencing was obtained for 15 of 22 (68%) patients. Of these 15 extreme PSA responders with sequencing data available, All 15 of 15 (100%) harbored a pathogenic mutation in TP53 and/or a homologous recombination DNA repair (HRD) gene. Among the subset of patients with measureable disease (N = 15), 10 patients (67%) achieved an objective response including one patient with a complete response. The median radiographic progression-free survival of these deep PSA responders was 11.3 months (95% CI, 7.9-25.0 months).

CONCLUSIONS

We observed an enrichment of TP53 and HRD mutations in mCRPC patients with extreme PSA responses to BAT, with durability lasting about a year. These data support the hypothesis that BAT may most benefit patients with DNA repair-deficient mCRPC. Further studies of BAT in biomarker-selected mCRPC populations (ie, TP53/HRD-mutated) are warranted.

Supraphysiologic Testosterone Induces Ferroptosis and Activates Immune Pathways through Nucleophagy in Prostate Cancer

The discovery that androgens play an important role in the progression of prostate cancer led to the development of androgen deprivation therapy (ADT) as a first line of treatment. However, paradoxical growth inhibition has been observed in a subset of prostate cancer upon administration of supraphysiologic levels of testosterone (SupraT), both experimentally and clinically. Here we report that SupraT activates cytoplasmic nucleic acid sensors and induces growth inhibition of SupraT-sensitive prostate cancer cells. This was initiated by the induction of two parallel autophagy-mediated processes, namely, ferritinophagy and nucleophagy. Consequently, autophagosomal DNA activated nucleic acid sensors converge on NFκB to drive immune signaling pathways. Chemokines and cytokines secreted by the tumor cells in response to SupraT resulted in increased migration of cytotoxic immune cells to tumor beds in xenograft models and patient tumors. Collectively, these findings indicate that SupraT may inhibit a subset of prostate cancer by activating nucleic acid sensors and downstream immune signaling. SIGNIFICANCE: This study demonstrates that supraphysiologic testosterone induces two parallel autophagy-mediated processes, ferritinophagy and nucleophagy, which then activate nucleic acid sensors to drive immune signaling pathways in prostate cancer.

Detection of Early Progression with 18F-DCFPyL PET/CT in Men with Metastatic Castration-Resistant Prostate Cancer Receiving Bipolar Androgen Therapy

Bipolar androgen therapy (BAT) is an emerging treatment for metastatic castration-resistant prostate cancer (mCRPC). ¹⁸F-DCFPyL is a small-molecule PET radiotracer targeting prostate-specific membrane antigen (PSMA). We analyzed the utility of ¹⁸F-DCFPyL PET/CT in determining clinical response to BAT. Methods: Six men with mCRPC receiving BAT were imaged with ¹⁸F-DCFPyL PET/CT at baseline and after 3 mo of treatment. Progression by PSMA-targeted PET/CT was defined as the appearance of any new ¹⁸F-DCFPyL-avid lesion. Results: Three of 6 (50%) patients had progression on ¹⁸F-DCFPyL PET/CT. All 3 had stable disease or better on contemporaneous conventional imaging. Radiographic progression on CT or bone scanning was observed within 3 mo of progression on ¹⁸F-DCFPyL PET/CT. For the 3 patients who did not have progression on ¹⁸F-DCFPyL PET/CT, radiographic progression was not observed for at least 6 mo. Conclusion: New radiotracer-avid lesions on ¹⁸F-DCFPyL PET/CT in men with mCRPC undergoing BAT can indicate early progression.

Local and Regional Recurrences of Clinically Localized Renal Cell Carcinoma after Nephrectomy: A 15 Year Institutional Experience with Prognostic Features and Oncologic Outcomes

OBJECTIVE

To evaluate outcomes for patients with local recurrence (LR) of clinically localized renal cell carcinoma (RCC) without concurrent systemic metastasis from our institution, an event that occurs rarely (1%-3%) after surgery. LR may be a harbinger of poor outcomes, and the best management of these patients is unclear.

MATERIALS/METHODS

We retrospectively reviewed patients surgically treated for clinically localized RCC (cT1-2N0M0) with subsequent LR (in the partial or radical nephrectomy bed) and/or regional recurrence (RR; in the abdomen distant from the direct site of surgery) without concurrent metastasis from our institutional database (2004-2018). Comparative and survival analyses were performed.

RESULTS

Out of 3038 total patients, 1895 had clinically localized RCC, with 30 patients (1.6%) having isolated LR/RR. Median time to recurrence was 26.5 months (IQR:16-35). Of 26 patients treated with local therapy, 14 (53.8%) recurred over a median follow-up time of 29.5 months (IQR:12-45). The 1-year and 2-year secondary recurrence-free survival rates are 60.7% and 49.7%, respectively. Two or more sites of locoregional recurrence significantly predicted secondary recurrence/metastasis after local therapy for local recurrence (hazard ratio: 2.22, P= .04).

CONCLUSION

Our results suggest local therapy is appropriate for select patients with LR/RR, with almost 50% of patients undergoing a second local therapy remaining alive with "local cure" and no secondary recurrence. The number of sites of recurrence can be used to better select patients that will benefit from local therapy or systemic/combination therapy. This work provides a framework onto which further studies regarding local therapy and locoregional recurrence of RCC can be performed.

The European Association of Urology Biochemical Recurrence Risk Groups Predict Findings on PSMA PET in Patients with Biochemically Recurrent Prostate Cancer after Radical Prostatectomy

Purpose: To evaluate the association of a new biochemical recurrence (BCR) risk stratification system with PSMA-targeted PET/CT findings. Methods: Two prospective studies that included patients with BCR were pooled. Findings on PSMA PET were catalogued. Patients were characterized according to the European Association of Urology (EAU) BCR risk categories. Univariable and multivariable analyses were carried out by logistic regression. Results: 145 patients were included (45 low-risk and 100 high-risk). High-risk BCR patients had a higher positive rate when compared to low-risk (82.0% vs. 48.9%; P < 0.001), and reached independent predictor status for positive PSMA PET/CT scan on multivariable logistic regression (OR 6.73, 95% CI 2.41-18.76; P < 0.001). The AUC using the combination of BCR risk group and PSA was higher than PSA alone (0.834 vs. 0.759, P = 0.015). Conclusion: The EAU BCR risk group defines the best candidates who can benefit from a PSMA PET/CT scan when BCR occurs.

Abstract 2404: Increased mitochondrial DNA copy number occurs during prostate cancer progression and in cancer precursor lesions across multiple organs

Accurately measuring mitochondrial DNA copy number (mtDNAcn) is important for improving our understanding of cancer biology. Prior studies have revealed differences in mtDNAcn between matched bulk tumor-normal pairs from a range of different organs. However, there is little consistency across tumor types; compared to their normal tissue counterparts, some cancers appear to have increased mtDNAcn, others appear to have decreased mtDNAcn, and in others, such as prostate cancer, studies have shown contradictory results. The lack of consistency of mtDNAcn changes in tumor-normal pairs may reflect a failure to address the marked heterogeneity in mtDNAcn across different cell types within normal tissues. In addition, tumor cell heterogeneity in mtDNAcn has also not been taken into account in most prior studies, which can further confound tumor-normal comparisons. Finally, little is known about mtDNAcn alterations in cancer precursor lesions. To address these technical limitations, we combined a recently introduced quantitative in situ hybridization method with immunohistochemistry in a multiplex assay. This enabled us to measure mtDNAcn using digital image analysis in specific cell populations of interest on formalin fixed paraffin embedded (FFPE) and frozen tissue samples. We determined that normal prostate basal cells have approximately 3-fold higher mtDNA levels than normal prostate luminal cells. Compared to the adjacent normal prostate glands, we found markedly increased levels of mtDNA in high-grade prostatic intraepithelial neoplasia (HGPIN), the presumptive precursor lesions to most prostate cancers. We also found increased levels as well as heterogeneity of mtDNAcn in invasive prostate cancer lesions, and more consistently elevated levels in castration-resistant metastatic prostate cancer (CRPC). Increased mtDNA copy number was also identified by whole genome sequencing and quantitative PCR from laser capture micro-dissected human prostate tumor-normal pairs. We also observed higher mtDNAcn in two other precancer lesion types, pancreatic intraepithelial neoplasia and colorectal adenomas. Our approach represents a technological advance as it facilitates mtDNAcn measurements in a manner that preserves morphology, allowing for the evaluation of specific cell populations of interest. These findings raise the hypothesis that increased mitochondrial mass and function may drive the development of precancerous lesions in the prostate, pancreas and colon, as well as invasive prostate cancer development and progression.

Citation Format: Jiayu Chen, Qizhi Zheng, Jessica L. Hicks, Levent Trabzonlu, Emmanuel S. Antonarakis, Mark C. Markowski, Samuel R. Denmeade, Busra Ozbek, Anuj Gupta, Tatianna C. Larman, Ralph H. Hruban, Sarah Wheelan, Srinivasan Yegnasubramanian, Angelo M. De Marzo. Increased mitochondrial DNA copy number occurs during prostate cancer progression and in cancer precursor lesions across multiple organs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2404.

TRANSFORMER: A Randomized Phase II Study Comparing Bipolar Androgen Therapy Versus Enzalutamide in Asymptomatic Men With Castration-Resistant Metastatic Prostate Cancer

PURPOSE

Prostate cancer (PCa) becomes resistant to androgen ablation through adaptive upregulation of the androgen receptor in response to the low-testosterone microenvironment. Bipolar androgen therapy (BAT), defined as rapid cycling between high and low serum testosterone, disrupts this adaptive regulation in castration-resistant PCa (CRPC).

METHODS

The TRANSFORMER (Testosterone Revival Abolishes Negative Symptoms, Fosters Objective Response and Modulates Enzalutamide Resistance) study is a randomized study comparing monthly BAT (n = 94) with enzalutamide (n = 101). The primary end point was clinical or radiographic progression-free survival (PFS); crossover was permitted at progression. Secondary end points included overall survival (OS), prostate-specific antigen (PSA) and objective response rates, PFS from randomization through crossover (PFS2), safety, and quality of life (QoL).

RESULTS

The PFS was 5.7 months for both arms (hazard ratio [HR], 1.14; 95% CI, 0.83 to 1.55; P = .42). For BAT, 50% decline in PSA (PSA50) was 28.2% of patients versus 25.3% for enzalutamide. At crossover, PSA50 response occurred in 77.8% of patients crossing to enzalutamide and 23.4% to BAT. The PSA-PFS for enzalutamide increased from 3.8 months after abiraterone to 10.9 months after BAT. The PFS2 for BAT→enzalutamide was 28.2 versus 19.6 months for enzalutamide→BAT (HR, 0.44; 95% CI, 0.22 to 0.88; P = .02). OS was 32.9 months for BAT versus 29.0 months for enzalutamide (HR, 0.95; 95% CI, 0.66 to 1.39; P = .80). OS was 37.1 months for patients crossing from BAT to enzalutamide versus 30.2 months for the opposite sequence (HR, 0.68; 95% CI, 0.36 to 1.28; P = .225). BAT adverse events were primarily grade 1-2. Patient-reported QoL consistently favored BAT.

CONCLUSION

This randomized trial establishes meaningful clinical activity and safety of BAT and supports additional study to determine its optimal clinical integration. BAT can sensitize CRPC to subsequent antiandrogen therapy. Further study is required to confirm whether sequential therapy with BAT and enzalutamide can improve survival in men with CRPC.

Bipolar androgen therapy sensitizes castration-resistant prostate cancer to subsequent androgen receptor ablative therapy

BACKGROUND

Cyclical, high-dose testosterone administration, termed bipolar androgen therapy (BAT), can induce clinical responses and restore sensitivity to androgen signalling inhibition in patients with previously treated castration-resistant prostate cancer (PCa) (CRPC). This trial evaluated whether BAT is a safe and effective first-line hormonal therapy for patients with CRPC.

PATIENTS AND METHODS

In cohort C of this single-centre, open-label, phase II, multi-cohort trial (RE-sensitizing with Supraphysiologic Testosterone to Overcome REsistance study), 29 patients with CRPC received first-line hormonal therapy with 400 mg of testosterone cypionate intramuscularly every 28 days concurrent with a luteinising hormone-releasing hormone agonist/antagonist. The primary end-point of the study was the PSA₅₀ response rate to BAT treatment.

RESULTS

After treatment with BAT, four of 29 patients (14%; 95% confidence interval [CI]: 4-32%) experienced a PSA₅₀ response. The median radiographic progression-free survival to BAT was 8.5 months (95% CI: 6.9-15.1) for patients with metastatic CRPC. After progression on BAT, 17 of 18 patients (94%; 95% CI: 73-100%) achieved a PSA₅₀ response and 15 of 18 patients (83%; 95% CI: 59-96) achieved a PSA₉₀ response on abiraterone or enzalutamide. Twelve of 15 patients (80%; 95% CI: 52-96) with metastatic CRPC remain on abiraterone or enzalutamide with a median duration of follow-up of 11.2 months.

CONCLUSION

As first-line hormonal treatment for CRPC, BAT was well tolerated and resulted in prolonged disease stabilisation. After progression on BAT, patients had favourable responses to second-generation androgen receptor-targeted therapy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02090114.

Abstract 2410: Supraphysiological androgens induce ferroptotic cell death in prostate cancer cells

Castration resistant prostate cancer (CRPC) first manifests as a sustained rise in the androgen-responsive gene, PSA, consistent with reactivation of a functioning androgen receptor (AR) axis. This observation led to the development of “second-line” therapies aimed at further blocking androgen/AR signaling. Unfortunately, resistance to these agents can also develop quickly. Paradoxically, several studies have suggested that the growth of AR-positive human CRPC cell lines may be inhibited by supraphysiologic levels of testosterone (SupT). These studies suggested that the adaptive reliance on AR signaling by CRPC cells becomes a therapeutic liability that can be exploited through the administration of SupT, which we termed as bipolar androgen therapy (BAT). Understanding how BAT works at the molecular and cellular levels might help in rationally combining BAT with other agents to achieve increased efficacy and tumor responses. Our data indicates that SupT induces autophagy mediated degradation of ferritin in prostate cancer (PCa) cells. Degradation of ferritin results in increase in labile iron pool increasing lipid peroxidation. Our data further indicates that SupT distinctly induces ferroptosis, a nonapoptotic regulated form of cell death induced by the accumulation of labile iron. Ferroptosis is thought to have tumor suppressing capabilities by clearing tumor cells via immune system activation. BAT has been discussed as a potential therapy for prostate cancer, but further research is needed to understand its full potential. Future combination of BAT with existing immunotherapeutics including immune checkpoint blockade may prove beneficial for treatment of CRPC.

Citation Format: Rajendra Kumar, Kavya Boyapati, Naiju Thomas, Deven Topiwala, Suthicha Kanacharoen, Olutosin Owoyemi, Max Coffey, Michael Carducci, Mark C. Markowski, Emmanuel S. Antonarakis, Drew Pardoll, Samuel Denmeade, Sushant K. Kachhap. Supraphysiological androgens induce ferroptotic cell death in prostate cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2410.

Extreme responses to immune checkpoint blockade following bipolar androgen therapy and enzalutamide in patients with metastatic castration resistant prostate cancer

BACKGROUND

Immune checkpoint inhibition has been shown to have limited efficacy in patients with metastatic prostate cancer. Prostate cancers that harbor certain homologous recombination (HR) DNA repair gene mutations, inactivating CDK12 mutations or have underlying mismatch repair deficiency may be effectively treated with immunotherapy. Combination therapy may improve clinical response rates to immune checkpoint blockade. We observed profound prostate-specific antigen (PSA) and/or objective responses to immune checkpoint blockade following prior treatment with bipolar androgen therapy (BAT) and enzalutamide.

METHODS

We report three cases of patients with metastatic castration resistant prostate cancer (mCRPC) undergoing therapy with anti-PD-1 inhibitors. All patients underwent both somatic molecular testing and germline genetic testing.

RESULTS

Two of the three patients with mCRPC harbored an inactivating mutation in an HR DNA repair gene (BRCA2, ATM). No patient demonstrated mismatch repair deficiency, nor were CDK12 alterations present. All three patients had been treated with BAT and enzalutamide before immune checkpoint blockade, a paradoxical approach for the treatment of mCRPC developed by our group.

CONCLUSIONS

These cases of mCRPC suggest that immune checkpoint blockade may have therapeutic potential in patients with prostate cancer, especially following immune activation ("priming") using BAT and enzalutamide.

Phase 1 Study of Molibresib (GSK525762), a Bromodomain and Extra-Terminal Domain Protein Inhibitor, in NUT Carcinoma and Other Solid Tumors

BACKGROUND

Bromodomain and extra-terminal domain proteins are promising epigenetic anticancer drug targets. This first-in-human study evaluated the safety, recommended phase II dose, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of the bromodomain and extra-terminal domain inhibitor molibresib (GSK525762) in patients with nuclear protein in testis (NUT) carcinoma (NC) and other solid tumors.

METHODS

This was a phase I and II, open-label, dose-escalation study. Molibresib was administered orally once daily. Single-patient dose escalation (from 2 mg/d) was conducted until the first instance of grade 2 or higher drug-related toxicity, followed by a 3 + 3 design. Pharmacokinetic parameters were obtained during weeks 1 and 3. Circulating monocyte chemoattractant protein-1 levels were measured as a pharmacodynamic biomarker.

RESULTS

Sixty-five patients received molibresib. During dose escalation, 11% experienced dose-limiting toxicities, including six instances of grade 4 thrombocytopenia, all with molibresib 60-100 mg. The most frequent treatment-related adverse events of any grade were thrombocytopenia (51%) and gastrointestinal events, including nausea, vomiting, diarrhea, decreased appetite, and dysgeusia (22%-42%), anemia (22%), and fatigue (20%). Molibresib demonstrated an acceptable safety profile up to 100 mg; 80 mg once daily was selected as the recommended phase II dose. Following single and repeat dosing, molibresib showed rapid absorption and elimination (maximum plasma concentration: 2 hours; t1/2: 3-7 hours). Dose-dependent reductions in circulating monocyte chemoattractant protein-1 levels were observed. Among 19 patients with NC, four achieved either confirmed or unconfirmed partial response, eight had stable disease as best response, and four were progression-free for more than 6 months.

CONCLUSIONS

Once-daily molibresib was tolerated at doses demonstrating target engagement. Preliminary data indicate proof-of-concept in NC.

PSA Doubling Time and Absolute PSA Predict Metastasis-free Survival in Men With Biochemically Recurrent Prostate Cancer After Radical Prostatectomy

INTRODUCTION

The aim of this study was to investigate the association of prostate-specific antigen (PSA) values on metastasis-free survival (MFS) in men with biochemically recurrent prostate cancer (BRPC) and PSA doubling time (PSADT) < 12 months. This dataset also reflects an update with longer follow-up of our prior publications on the natural history of BRPC in the absence of treatment.

MATERIALS AND METHODS

In this report, we combined databases from the Center for Prostate Disease Research and Johns Hopkins University (CPDR/JHU). In the CPDR/JHU radical prostatectomy database (30,936 total patients), 656 men with BRPC (> 0.2 ng/mL) after prostatectomy and PSADT < 12 months, who received no adjuvant/salvage androgen deprivation and/or radiation therapy, were prospectively followed until radiologic evidence of metastasis and are included in this analysis.

RESULTS

Metastasis occurred in 250 of 656 patients with BRPC (median follow-up, 5 years). PSADT < 7.5 months and Gleason score were independent risk factors for distant metastasis in multivariable analysis. Risk of metastasis increased for PSADT 6.01 to 7.50, 4.51 to 6.0, 3.01 to 4.50, and ≤ 3.0 months, after adjusting for Gleason score. A PSA value ≥ 0.5 ng/mL significantly and independently increased risk of metastasis in patients with PSADT < 12 months (hazard ratio, 2.79; 95% confidence interval, 1.47-5.29; P = .001).

CONCLUSIONS

In men with PSADT < 12 months, PSADT ≤ 7.5 months, PSA ≥ 0.5 ng/mL, and Gleason score are independent predictors of MFS on multivariable analysis.

Improved identification of patients with oligometastatic clear cell renal cell carcinoma with PSMA-targeted 18F-DCFPyL PET/CT

OBJECTIVE

Complete surgical resection of metastatic sites has been shown to prolong survival in select patients with oligometastatic RCC. This treatment strategy is dependent upon the accurate characterization of a patient's extent of disease. The objective of this study was to explore the utility of PSMA-targeted ¹⁸F-DCFPyL PET/CT in patients with presumed oligometastatic clear cell RCC.

METHODS

This is a subset analysis of a prospective study in which patients with RCC were imaged with ¹⁸F-DCFPyL PET/CT (ClinicalTrials.gov identifier NCT02687139). In the present analysis, patients with oligometastatic clear cell RCC, defined as ≤ 3 metastatic lesions on conventional imaging, were evaluated. ¹⁸F-DCFPyL PET/CT scans were reviewed for sites of disease and compared to conventional imaging.

RESULTS

The final cohort included 14 patients with oligometastatic clear cell RCC. Conventional imaging revealed 21 metastatic lesions and 3 primary tumors. ¹⁸F-DCFPyL PET/CT detected 29 sites of metastatic disease and 3 primary tumors. Of the 21 metastatic lesions detected on conventional imaging, 17 (81.0%) had radiotracer uptake. Additionally, all 3 primary tumors had radiotracer uptake. In 4 (28.6%) patients a total of 12 more lesions were identified on ¹⁸F-DCFPyL PET/CT than conventional imaging. Notably, 3 (21.4%) patients were no longer considered oligometastatic. The detection rates of conventional imaging and ¹⁸F-DCFPyL PET/CT for identifying sites of disease were 66.7% and 88.9%, respectively.

CONCLUSIONS

PSMA-targeted PET/CT appears to aid in the identification of patients with oligometastatic clear cell RCC. If borne out in future studies, this suggests that PSMA-targeted imaging has the potential to help select candidates for metastasis-directed therapy.

Molecular Characterization and Clinical Outcomes of Primary Gleason Pattern 5 Prostate Cancer After Radical Prostatectomy

PURPOSE

Very high-risk prostate cancer (PC) is associated with poor response to local and systemic treatments; however, few cases have been molecularly profiled. We studied clinical outcomes and molecular profiles of patients with clinically localized primary Gleason pattern 5 PC.

PATIENTS AND METHODS

Clinicopathologic features, targeted somatic and germline sequencing, and PTEN, TP53, and ERG status by immunohistochemistry were assessed in patients undergoing surgery from 2005 to 2015; 60 consecutive patients were identified with Gleason score 5 + 4 = 9 or 5 + 5 = 10 PC after radical prostatectomy with available tissue and clinical follow-up. Clinicopathologic and genomic parameters were correlated with biochemical relapse, metastasis-free survival, time to castration resistance, and overall survival using Cox proportional hazards models.

RESULTS

Of patients with somatic sequencing data and clinical follow-up, 34% had DNA repair gene mutations, including 22% (11 of 49) with homologous recombination and 12% (six of 49) with mismatch repair gene alterations. Homologous recombination mutations were germline in 82% (nine of 11) of patients. In addition, 33% (16 of 49) had TP53 mutation, and 51% (29 of 57) had PTEN loss. Overall, 43% developed metastasis, with a time to castration resistance of 12 months. On multivariable analysis of clinicopathologic variables, only ductal/intraductal histology (hazard ratio, 4.43; 95% CI, 1.76 to 11.15; P = .002) and seminal vesicle invasion (hazard ratio, 5.14; 95% CI, 1.83 to 14.47; P = .002) were associated with metastasis. Among genomic alterations, only TP53 mutation and PTEN loss were associated with metastasis on univariable analysis, and neither remained significant in multivariable analyses. These data are retrospective and hypothesis generating.

CONCLUSION

Potentially actionable homologous recombination and mismatch repair alterations are observed in a significant proportion of patients with very high-risk PC at the time of radical prostatectomy. These findings could inform the design of prospective trials in this patient population.

Wnt-pathway Activating Mutations Are Associated with Resistance to First-line Abiraterone and Enzalutamide in Castration-resistant Prostate Cancer

BACKGROUND

Wnt signaling is a cellular pathway involved in embryogenesis, development, and neoplasia. Wnt-pathway activation may accelerate prostate cancer androgen-independent growth and mediate antiandrogen resistance. Since 10-20% of advanced prostate cancers harbor Wnt-activating mutations, we aimed to characterize the clinical features and response to novel antiandrogens in such patients.

OBJECTIVE

To determine whether men with metastatic castration-resistant prostate cancer (mCRPC) who harbor Wnt-pathway mutations have poorer responses to first-line novel hormonal therapies: abiraterone/enzalutamide.

DESIGN, SETTING, AND PARTICIPANTS

Patients with mCRPC who received first-line abiraterone or enzalutamide were retrospectively evaluated. Using tumor DNA analyses, we queried for activating mutations in CTNNB1 or inactivating mutations in APC or RNF43, all of which are predicted to stimulate Wnt signaling. Presence or absence of at least one Wnt-activating alteration was correlated with clinical-pathologic characteristics and treatment outcomes.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Time to prostate-specific antigen (PSA) progression, overall survival (OS), and PSA response were measured. Cox regression models were used to test associations between Wnt status and clinical-pathologic outcomes; Kaplan-Meier and log-rank analyses were used to compare time-to-event endpoints.

RESULTS AND LIMITATIONS

Of 137 patients evaluated, 11% (n=15) had tumor DNA analysis showing at least one Wnt-stimulating alteration. Patients with Wnt-activating mutations had numerically fewer T3/T4 tumors than Wnt wild-type patients (31% vs 51%), but were otherwise generally balanced. Median time to PSA progression on first-line abiraterone/enzalutamide was shorter in Wnt-activated patients (6.5 vs 9.6mo, hazard ratio [HR] 2.34, p=0.003), as was OS (23.6 vs 27.7mo, HR 2.28, p=0.01). PSA responses were numerically worse in Wnt-activated patients (53% vs 75%, p=0.12). Presence of Wnt-activating alterations (adjusted HR [aHR] 2.33, p=0.007) and use of previous chemotherapy (aHR 1.83, p=0.004) were both independently associated with increased hazard of progression.

CONCLUSIONS

Patients with somatic Wnt-pathway activating mutations have worse outcomes to first-line abiraterone/enzalutamide than Wnt wild-type patients. Our data suggest that additional genomically informed therapies are needed for this relevant subset of mCRPC patients.

PATIENT SUMMARY

In this report, we retrospectively examined outcomes of metastatic prostate cancer patients with or without Wnt-pathway mutations who received abiraterone or enzalutamide for the first time, in order to examine whether these mutations affect the prognosis. Our study suggested that patients who have Wnt-pathway activating mutations derived less benefit from abiraterone and enzalutamide when compared to patients without these mutations. We conclude that Wnt-pathway mutations might decrease the effectiveness of abiraterone and enzalutamide, and we propose that the Wnt pathway might be a good therapeutic target for these patients, in order to potentially reverse or prolong resistance to abiraterone and enzalutamide in men with Wnt mutations.

Inconsistent Detection of Sites of Metastatic Non-Clear Cell Renal Cell Carcinoma with PSMA-Targeted [18F]DCFPyL PET/CT

PURPOSE

To investigate the utility of prostate-specific membrane antigen (PSMA)-targeted [¹⁸F]DCFPyL positron emission tomography (PET)/X-ray computed tomography (CT) imaging for the detection of sites of disease in patients with metastatic non-clear cell renal cell carcinoma (RCC).

PROCEDURES

Eight patients with metastatic non-clear cell RCC underwent imaging with PSMA-targeted [¹⁸F]DCFPyL PET/CT. Imaged RCC histologic subtypes included papillary RCC (n = 3), chromophobe RCC (n = 2), unclassified RCC (n = 2), and Xp11 translocation RCC (n = 1). Using comparison to conventional CT and/or magnetic resonance imaging as reference, two radiologists with expertise in nuclear medicine identified putative sites of disease on [¹⁸F]DCFPyL PET/CT and classified each lesion as having no radiotracer uptake, equivocal uptake, or definitive uptake.

RESUTS

In total, 73 metastatic sites and 3 primary tumors compatible with sites of non-clear cell RCC were identified on conventional imaging. Metastatic sites of disease included lymph nodes (n = 40), venous thrombi (n = 3), pulmonary nodules (n = 10), bone lesions (n = 15), brain lesions (n = 3), and retroperitoneal masses (n = 2). Only 10 of the 73 lesions (13.7 %) were classified as having definitive radiotracer uptake (median SUV_max = 3.25, range = 1.2-9.5), 14 lesions (19.2 %) had equivocal uptake (median SUV_max = 2.85, range = 0.5-6.5), and 49 lesions (67.1 %) had no definitive uptake above background (median SUV_max = 1.7, range = 0.2-3.0). The three primary renal tumors demonstrated lower radiotracer avidity relative to surrounding normal renal parenchyma.

CONCLUSIONS

A small proportion of sites of non-clear cell RCC showed uptake of the PSMA-targeted radiotracer [¹⁸F]DCFPyL. Unlike for clear cell RCC, the results of this study indicate that PSMA-based PET is not appropriate for imaging other RCC subtypes.

Efficacy of Radium-223 in Bone-metastatic Castration-resistant Prostate Cancer with and Without Homologous Repair Gene Defects

BACKGROUND

Pathogenic mutations in genes mediating homologous recombination (HR) DNA repair are present in 20-30% of men with metastatic castrate-resistant prostate cancer (mCRPC). Radium-223 is a bone-seeking α-emitter that induces double-strand DNA breaks, thereby killing cancer cells in the bone microenvironment.

OBJECTIVE

To evaluate the potential impact of germline or somatic HR-deficiency (HRD) mutations on radium-223 efficacy in mCRPC with bone metastasis.

DESIGN, SETTING, AND PARTICIPANTS

This is a retrospective single-institution study. Medical records of 190 mCRPC patients for whom germline and/or somatic DNA sequencing data were available were reviewed. Of these patients, 28 had received standard-of-care radium-223 at Johns Hopkins between February 2013 and February 2018.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Alkaline phosphatase (ALP) responses and time-to-ALP-progression were the coprimary endpoints. Prostate-specific antigen (PSA) responses, overall survival (OS), and time to next systemic therapy were also evaluated.

RESULTS AND LIMITATIONS

Of the 28 patients included, 10 men (35.7%) had a germline/somatic HRD mutation (three in BRCA2, and one each in ATM, ATR, CHEK2, FANCG, FANCI, FANCL, and PALB2) and 18 (64.3%) did not. Men with HRD mutations (HRD+) had numerically lower ages (66 vs 73yr, p=0.25), more soft-tissue metastases (50% vs 38%, p=0.43), and higher baseline ALP levels (130 vs 108 U/l, p=0.84). Compared with HRD(-) men, HRD(+) patients showed greater ALP responses (80% vs 39%, p=0.04), longer time to ALP progression (median10.4 vs 5.8mo, hazard ratio [HR] 6.4, p=0.005), and a trend toward longer OS (median 36.9 vs 19.0mo, HR 3.3, p=0.11). PSA responses (0% vs 0%, p>0.99) and time to next systemic therapy (HR 1.5, p=0.39) were similar between the two groups. Results are limited by the retrospective nature of the analysis and the small sample size.

CONCLUSIONS

In this exploratory study, bone-metastatic CRPC patients with inactivating HRD mutations demonstrated significantly improved ALP responses and time to ALP progression. These results should motivate prospective validation of the "synthetic lethality" hypothesis between HRD mutations and radium-223 activity.

PATIENT SUMMARY

In this report, we retrospectively examined outcomes to metastatic prostate cancer in patients with and without DNA repair mutations who received radium-223, a therapy that kills cancer cells by causing direct DNA damage. Our study suggested that patients who have inherited or acquired DNA repair gene mutations derived greater benefit from radium-223 when compared with patients without these mutations. We concluded that radium-223 might have an important role in this setting; however, prospective studies are needed to confirm whether DNA repair mutations truly make radium-223 work better or not.

Characterization of novel cell lines derived from a MYC-driven murine model of lethal metastatic adenocarcinoma of the prostate

BACKGROUND

Loss or mutation of PTEN alleles at 10q23 in combination with 8q24 amplification (encompassing MYC) are common findings in aggressive, human prostate cancer. Our group recently developed a transgenic murine model of prostate cancer involving prostate-specific Pten deletion and forced expression of MYC under the control of the Hoxb13 promoter. MYC overexpression cooperated with Pten loss to recapitulate lethal, human prostate cancer.

METHOD

We now report on the generation of two mouse prostate cancer cell lines, BMPC1 and BMPC2, derived from a lymph node, and liver metastasis, respectively.

RESULTS

Both cell lines demonstrate a phenotype consistent with adenocarcinoma and grew under standard tissue culture conditions. Androgen receptor (AR) protein expression is minimal (BMPC1) or absent (BMPC2) consistent with AR loss observed in the BMPC mouse model of invasive adenocarcinoma. Growth in media containing charcoal-stripped serum resulted in an increase in AR mRNA in BMPC1 cells with no effect on protein expression, unless androgens were added, in which case AR protein was stabilized, and showed nuclear localization. AR expression in BMPC2 cells was not effected by growth media or treatment with androgens. Treatment with an anti-androgen/castration or androgen supplemented media did not affect in vitro or in vivo growth of either cell line, irrespective of nuclear AR detection.

DISCUSSION

These cell lines are a novel model of androgen-insensitive prostatic adenocarcinoma driven by MYC over-expression and Pten loss.

Abstract 129: Biobanking and feasibility considerations for prostate cancer gastrointestinal microbiome studies

The human microbiome may play a role in prostate health and disease as both direct and indirect interactions. Direct interactions between microbiota and prostate cancer include prostate infections, inflammation, prostatitis, and potentially interactions with the urinary microbiome. Indirectly, the gastrointestinal (GI) microbiota may influence prostate cancer via xenobiotic metabolism, augmentation of treatment response, and contributions to systemic inflammation and cytokines. In the present study, we are seeking to understand how different prostate cancer treatments may be affected by the microbial composition of the GI tract. We are currently developing a biorepository of fecal specimens from prostate cancer patients in different clinical states of disease. A key question during the planning phase of this biorepository was if samples can be collected and banked in the form of a rectal swab, instead of the more traditional method of a stool sample. Rectal swabs provide an advantage over collection of stool specimens in that they are easily collected (the patient can self-collect) in a standardized, “on demand” fashion during routine patient visits. Therefore, a pilot study was undertaken to compare the microbial profile of samples collected via both methods from the same individual. We concomitantly collected both stool samples and rectal swabs from 6 patients undergoing active surveillance for prostate cancer at the Johns Hopkins Hospital. All samples were stored at -80°C until we were ready to isolate bacterial DNA. DNA was extracted with a phenol:chloroform based protocol that we have optimized for microbiome studies that includes multiple enzyme digest and bead beating. We conducted Illumina amplicon sequencing of PCR products amplified with universal primers designed against the V6 hypervariable region of the bacterial 16S rRNA gene. We tested our sequencing strategy against Microbiome Reference Standards obtained from American Type Culture Collection (ATCC). The results of our analysis from prostate cancer patients indicated high similarity of bacterial profiles obtained for matched stool and swabs in 4 of the 6 patients. In both of the cases that were dissimilar, there was a greater representation of Enterobacteriaceae in the stool sample versus the swab. We conclude that collection of rectal swabs is a more feasible and convenient means of sampling the GI microbiota in prostate cancer patients, especially when aiming to conduct longitudinal studies with multiple sample collections to correlate microbiota profiles to treatments and/or treatment response. Due to the differences that were identified, we recommend deciding on the sample collection method at the onset of biobanking, and keeping the sampling method consistent throughout.

Citation Format: Sarah E. Ernst, Mark C. Markowski, Anuj Gupta, Sarah J. Wheelan, H. Ballentine Carter, Alan W. Partin, Cynthia L. Sears, Karen S. Sfanos. Biobanking and feasibility considerations for prostate cancer gastrointestinal microbiome studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 129.

Intraductal/ductal histology and lymphovascular invasion are associated with germline DNA-repair gene mutations in prostate cancer

BACKGROUND

Germline mutations in genes mediating DNA repair are common in men with recurrent and advanced prostate cancer, and their presence may alter prognosis and management. We aimed to define pathological and clinical characteristics associated with germline DNA-repair gene mutations, to facilitate selection of patients for germline testing.

METHODS

We retrospectively evaluated 150 unselected patients with recurrent or metastatic prostate cancer who were offered germline genetic testing by a single oncologist using a clinical-grade assay (Color Genomics). This platform utilizes next-generation sequencing from saliva to interrogate 30 cancer-susceptibility genes. Presence or absence of a deleterious germline mutation was correlated with histological and clinical characteristics, and with family history of cancer. All patients with DNA-sequence alterations (pathogenic or variants) were offered genetic counseling.

RESULTS

Between July 2016 and July 2017, 150 consecutive patients underwent germline testing; pathogenic mutations were identified in 21 men (14%). Among those with germline mutations, 9 (43%) were in BRCA2, 3 (14%) were in ATM, 3 (14%) were in CHEK2, and 2 (9%) were in BRCA1. While there were no associations between germline mutations and age, tumor stage, Gleason sum or family history; mutation-positive patients had lower median PSA levels at diagnosis (5.5 vs 8.6 ng/mL, P = 0.01) and unique pathologic features. Namely, men with germline mutations were more likely to harbor intraductal/ductal histology (48% vs 12%, P < 0.01) and lymphovascular invasion (52% vs 14%, P < 0.01). Finally, 44% of patients with a positive germline test would not have been offered genetic screening according to current National Comprehensive Cancer Network (NCCN) guidelines.

CONCLUSIONS

Presence of intraductal/ductal histology and lymphovascular invasion appear to be associated with pathogenic germline DNA-repair gene mutations in men with prostate cancer, and identification of these features may help to select patients for germline testing. NCCN guidelines may be inadequate in predicting which prostate cancer patients should undergo genetic screening.

BET inhibitors in metastatic prostate cancer: therapeutic implications and rational drug combinations

INTRODUCTION

The bromodomain and extra-terminal (BET) family of proteins are epigenetic readers of acetylated histones regulating a vast network of protein expression across many different cancers. Therapeutic targeting of BET is an attractive area of clinical development for metastatic castration-resistant prostate cancer (mCRPC), particularly due to its putative effect on c-MYC expression and its interaction with the androgen receptor (AR). Areas covered: We speculate that a combination approach using inhibitors of BET proteins (BETi) with other targeted therapies may be required to improve the therapeutic index of BET inhibition in the management of prostate cancer. Preclinical data has identified several molecular targets that may enhance the effect of BET inhibition in the clinic. This review will summarize the known preclinical data implicating BET as an important therapeutic target in advanced prostate cancer, highlight the ongoing clinical trials targeting this protein family, and speculate on rationale combination strategies using BETi together with other agents in prostate cancer. A literature search using Pubmed was performed for this review. Expert opinion: Use of BETi in the treatment of mCRPC patients may require the addition of a second novel agent.

Clinical Utility of CLIA-Grade AR-V7 Testing in Patients With Metastatic Castration-Resistant Prostate Cancer

PURPOSE

A splice variant of the androgen receptor, AR-V7, confers resistance to AR-targeted therapies (ATTs) but not taxane chemotherapies in patients with metastatic castration-resistant prostate cancer. Since August 2015, a clinical-grade assay to detect AR-V7 messenger RNA expression in circulating tumors cells (CTCs) has been available to providers through a Clinical Laboratory Improvement Amendments-certified laboratory at Johns Hopkins University.

METHODS

We contacted ordering providers of the first 150 consecutive tests by using a questionnaire-based survey to determine how the results of AR-V7 testing were used to influence clinical practice.

RESULTS

In all, 142 (95%) of 150 questionnaires were completed by 38 providers from 29 sites across the United States and Canada. AR-V7 test results were reported either as CTC- (28%), CTC+/AR-V7- (30%), or CTC+/AR-V7+ (42%). Prevalence of AR-V7 detection increased with prior exposure to ATTs (abiraterone and enzalutamide naïve, 22%; after abiraterone or enzalutamide, 35%; after abiraterone and enzalutamide, 43%). Overall, management was affected by AR-V7 testing in 53% of the patients and even more often with CTC+/AR-V7+ results. AR-V7+ patients were commonly switched from ATT to taxane chemotherapy (43%) or were offered a clinical trial (43%); management remained unchanged in only 14% of these patients. Overall, patients who had a change in management on the basis of AR-V7 testing were significantly more likely to achieve a physician-reported 50% decline in prostate-specific antigen response on next-line therapy than those who did not change treatment (54% v 31%; P = .015).

CONCLUSION

Providers used AR-V7 testing to influence clinical decision making more often than not. Physicians reported thatmenwithAR-V7+results had the most treatment changes, and such men were preferentially managed with taxane therapy or offered a clinical trial, which may have improved outcomes.

Cost-Savings Analysis of AR-V7 Testing in Patients With Metastatic Castration-Resistant Prostate Cancer Eligible for Treatment With Abiraterone or Enzalutamide

INTRODUCTION

Identification of cancer biomarkers that inform clinical decisions and reduce the use of ineffective therapies is a major goal of precision oncology. An abnormal splice variant of the androgen receptor, AR-V7, was recently found to confer resistance to novel hormonal therapies (abiraterone and enzalutamide) in men with metastatic castration-resistant prostate cancer (mCRPC), but did not negatively affect responses to taxane chemotherapies, suggesting that early use of chemotherapy may be a more effective option for AR-V7(+) patients.

METHODS

We calculated the cost savings of performing AR-V7 testing in mCRPC patients prior to starting abiraterone/enzalutamide (and avoiding these drugs in AR-V7(+) men) versus treating all mCRPC patients empirically with abiraterone/enzalutamide (without use of the biomarker).

RESULTS

We determined that AR-V7 testing would result in substantial cost savings as long as the true prevalence of AR-V7 was >5%. In our prior studies, we estimated that approximately 30% of mCRPC patients may have detectable AR-V7 in circulating tumor cells (CTCs). In this population, upfront testing of AR-V7 status (at a price of $1,000 per test) would result in a net cost savings of $150 Million in the United States per year.

CONCLUSIONS

AR-V7 testing in mCRPC patients would be cost-beneficial when considering the current price of treatment, and may reduce the ineffective use of abiraterone/enzalutamide, leading to a significant net cost savings to the healthcare system. Clinical-grade AR-V7 testing is currently available at our institution. Prostate 76:1484-1490, 2016. © 2016 Wiley Periodicals, Inc.

Sarcomatoid Carcinoma of the Prostate: Retrospective Review of a Case Series From the Johns Hopkins Hospital

OBJECTIVE

To identify survival differences in patients with sarcomatoid prostate cancer based on initial staging and treatment regimens.

METHODS

We retrospectively reviewed the clinical outcomes of patients with a pathologically confirmed diagnosis of sarcomatoid prostate cancer. The primary statistical objective was to estimate overall survival (OS) and to assess the survival of patients at different stages treated with local and/or systemic approaches.

RESULTS

We identified 70 transurethral resections, needle biopsies, or prostatectomy specimens that were reviewed by the Department of Pathology at the Johns Hopkins Hospital from 2002-2012 and given the diagnosis of sarcomatoid prostate cancer. Of the 45 patients with available survival data, complete medical histories were obtained for 27 patients who were stratified based on a modified staging system (local disease, local disease with bladder invasion, and metastatic disease). After a median follow-up of 106 months, the median OS of patients in the local disease group was not reached. Notably, 5 of the 9 patients diagnosed with local disease survived >5 years and were treated with surgery and/or external beam radiation therapy. The OS hazard was significantly increased in patients with either clinical evidence of bladder invasion (HR: 20.46 [95% CI: 2.43,172]; P = 0.005) or metastatic disease (HR: 43.34 [95% CI: 4.39,427.4]; P = 0.001), which both demonstrated poor outcomes (median OS: local disease with bladder invasion-9 months; metastatic disease-7.1 months).

CONCLUSION

This retrospective analysis suggests that local sarcomatoid prostate cancer can be effectively treated with definitive therapy leading to favorable outcomes.

Therapy decisions for the symptomatic patient with metastatic castration-resistant prostate cancer

Metastatic prostate cancer continues to kill approximately 30,000 men per year. Since 2010, five new therapeutic agents have been Food and Drug Administration (FDA) approved to treat metastatic castration-resistant prostate cancer (mCRPC). With the increasing number of therapies available to clinicians, the most effective sequence in which to implement these treatments remains unknown. The presence or absence of symptoms (i.e., bony pain, visceral crisis) is a key parameter that informs the decision-making process regarding therapy. Treatment algorithms based on: 1) asymptomatic/minimal symptoms, 2) moderate symptoms or chemotherapy ineligible or 3) symptomatic disease need to be developed.

Inflammatory cytokines induce phosphorylation and ubiquitination of prostate suppressor protein NKX3.1

Inflammation of the prostate is a risk factor for the development of prostate cancer. In the aging prostate, regions of inflammatory atrophy are foci for prostate epithelial cell transformation. Expression of the suppressor protein NKX3.1 is reduced in regions of inflammatory atrophy and in preinvasive prostate cancer. Inflammatory cytokines tumor necrosis factor (TNF)-alpha and interleukin-1beta accelerate NKX3.1 protein loss by inducing rapid ubiquitination and proteasomal degradation. The effect of TNF-alpha is mediated via the COOH-terminal domain of NKX3.1 where phosphorylation of serine 196 is critical for cytokine-induced degradation. Mutation of serine 196 to alanine abrogates phosphorylation at that site and the effect of TNF-alpha on NKX3.1 ubiquitination and protein loss. This is in contrast to control of steady-state NKX3.1 turnover, which is mediated by serine 185. Mutation of serine 185 to alanine increases NKX3.1 protein stability by inhibiting ubiquitination and doubling the protein half-life. A third COOH-terminal serine at position 195 has a modulating effect on both steady-state protein turnover and on ubiquitination induced by TNF-alpha. Thus, cellular levels of the NKX3.1 tumor suppressor are affected by inflammatory cytokines that target COOH-terminal serine residues to activate ubiquitination and protein degradation. Our data suggest that strategies to inhibit inflammation or to inhibit effector kinases may be useful approaches to prostate cancer prevention.