Evaluating Immune Checkpoint Blockade in Metastatic Castration-Resistant Prostate Cancers with Deleterious CDK12 Alterations in the Phase 2 IMPACT Trial

PURPOSE

CDK12 inactivation in metastatic castration-resistant prostate cancer (mCRPC) may predict immunotherapy responses. This phase 2 trial evaluated the efficacy of immune checkpoint inhibitor (ICI) therapy in patients with CDK12-altered mCRPC.

PATIENTS AND METHODS

Eligible patients had mCRPC with deleterious CDK12 alterations and any prior therapies except ICI. Cohort A received ipilimumab (1 mg/kg) with nivolumab (3 mg/kg) every 3 weeks for up to 4 cycles, followed by nivolumab 480 mg every 4 weeks. Cohort C received nivolumab alone 480 mg every 4 weeks. Patients with CDK12-altered non-prostate tumors were enrolled in cohort B and not reported. The primary endpoint was 50% reduction in PSA (PSA50). Key secondary endpoints included PSA progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and safety.

RESULTS

PSA was evaluable in 23 patients in cohort A and 14 in cohort C. Median lines of prior therapy were 2 in cohorts A and C, including any prior novel hormonal agent (74% and 79%) and chemotherapy (57% and 36%). The PSA50 rate was 9% (95% CI 1-28%) in cohort A with 2 responders; neither had microsatellite instability or a tumor mutational burden ≥10 mutations/megabase. No PSA50 responses occurred in cohort C. Median PSA-PFS was 7.0 months (95% CI 3.6-11.4) in cohort A and 4.5 months (95% CI 3.4-13.8) in cohort C. Median OS was 9.0 months (95% CI 6.2-12.3) in cohort A and 13.8 months (95% CI 3.6-not reached) in cohort C.

CONCLUSIONS

There was minimal activity with ICI therapy in patients with CDK12-altered mCRPC.

Extragonadal germ cell tumors: A clinicopathologic study with emphasis on molecular features, clinical outcomes and associated secondary malignancies

Extragonadal germ cell tumors (EGCTs) are rare, representing <5% of all germ cell tumors (GCTs). Whilst EGCTs share morphological and immunohistochemical features with their gonadal counterparts, they tend to be more aggressive and are frequently associated with secondary somatic malignancies. The aim of our study was to evaluate the clinical, morphological and immunohistochemical features, and to analyze tumors for chromosomal abnormalities of 12p, in addition to any novel genetic alterations, in a series of EGCTs. Seventy-seven EGCTs were included. Anterior mediastinum was the most common anatomic site, followed by central nervous system, retroperitoneum, sacroccygeal area, and neck. Whole genome SNP array identified isochromosome 12p in 26% of tumors. Additional cytogenetic abnormalities included the presence of gain of chr 21 in 37% of tumors. Somatic-type malignancies were identified in 8% of patients. Disease progression (metastasis and/or recurrence) was documented in 8 patients, most of whom died from their relapse. Three patients who died of disease had somatic-type malignancies. Mediastinal seminomas had a significantly better overall survival when compared to mediastinal non-seminomatous GCTs. Our study demonstrates that EGCTs share similar histologic features, but diverse clinical outcomes compared to their gonadal counterparts. Outcomes vary according to anatomic location and histologic subtypes. Our data corroborate that somatic-type malignancies are frequently encountered in mediastinal EGCTs and that their presence portends a poorer prognosis.

Clinical impact of mutations in driver oncogenes and TP53/RB1 in advanced prostate cancer

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Background: Prostate cancer (PCa) is characterized by considerable genetic heterogeneity, and complex genomic features may influence prognosis and treatment response. We created a database of aggressive PCa that integrates comprehensive genomic sequencing with detailed clinical outcomes to better understand the optimal use of genomic sequencing. Methods: From 4/2005-7/2021, PCa cancer patients older than 18 years of age underwent tissue collection for tumoral RNA-sequencing and tumor/normal whole exome sequencing at our institution (HUM00046018, HUM00048105, HUM00067928, SU2C). Genomic and transcriptomic sequencing data was processed using Turnkey Precision Oncology. Genetic alterations, including ETS fusions, SPOP, FOXA1 class 1, and CDK12 mutations, as well as TP53 and RB1 mutations were analyzed. Clinical data was collected from 05/2021-01/2022, and clinical associations (metastasis free survival (MFS), time to castrate resistant prostate cancer (CRPC), and overall survival (OS)) were determined. Results: Data was available for 325 men. Median follow up from diagnosis was 106 months (IQR, 90-121), median age at diagnosis was 61 (IQR, 54-67), and most (91%) presented with PCa adenocarcinoma (n=292/325). At diagnosis, 51% (n=165) had localized, 5% (n=18) had clinical node positive, and 40% (n=128) had de-novo M1 disease. At time of tissue sampling, 87% (n=283) had metastatic disease, and 59% (n=192) were castrate resistant. Established PCa driver mutations included 140 ETS fusions (49%), 26 SPOP mutations (9%), 22 FOXA1 class 1 mutations (8%), and 15 (5%) CDK12 mutations. For men with localized disease at diagnosis (n=197/325), ETS fusion was associated with improved MFS (HR: 0.55; 95% CI: 0.37-0.81), time to CRPC (HR: 0.53; 0.35-0.80), and OS (HR: 0.56; 0.35-0.89). SPOP mutations were also associated with improved prognosis in this population (n=197/325): MFS (HR: 0.45; 0.24-0.84), time to CRPC (HR: 0.36; 0.18-0.73), and OS (HR: 0.46; 0.21-0.99). TP53 mutations were identified in 38% (n=122) of all patients and were associated with worse OS from the time of biopsy after adjusting for PCa castration state and disease spread at biopsy (HR: 2.2; 1.7-2.9, p<0.001). RB1 mutations were identified in 12% (n=40; 24/40 also TP53 mutants). OS from the time of biopsy was worse in the presence of dual TP53/RB1 mutants when compared to TP53 or RB1 mutants alone, independent of the disease state at time of biopsy (HR, 4.3; 95%CI: 2.7-7.0). Conclusions: In a cohort of aggressive PCa, oncogenic driver mutations were associated with significant differences in prognosis. ETS fusions and SPOP mutations correlated with improved outcomes for men with localized disease at presentation. TP53 loss was associated with worse prognosis, as was the combination with RB1 loss, across the disease spectrum. Future efforts will focus on correlating sensitivity to PCa treatments with genetic alterations throughout the disease course.

Clinical outcomes after utilization of PSMA PET scans in patients with biochemical recurrent prostate cancer

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Background: The optimal management of biochemical recurrent prostate cancer (BCR) remains unknown. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) scans can visualize micrometastatic disease, thus expanding treatment options for BCR from observation or androgen deprivation therapy (ADT) to potentially include metastasis-directed radiation (XRT) or next-generation hormonal agents (NHA). We aimed to describe how BCR patients were managed after PSMA PET scans and their clinical outcomes. Methods: We performed a retrospective chart review of 262 patients from the University of Michigan’s PSMA PET scan database (825 patients with scans 2017–2021). Patients who received maximal local therapy (defined as XRT alone n=199 or surgery + XRT n=63) are presented. Only patients with BCR and a minimum of 1 year follow-up after scans were included. Baseline patient and tumor characteristics, PSMA PET scan results, first and subsequent therapy delivered after PSMA PET, and prostate-specific antigen (PSA) and standard imaging results post PSMA PET were annotated. Primary endpoint is time from first post-scan therapy (within 6 months of scan) to subsequent therapy. Secondary outcomes include probability of no subsequent therapy in 1 year based on first post-scan therapy and PSMA scan findings and PSMA PET findings and association with Gleason score, PSA at BCR, and time from diagnosis to PSMA scan. Results: Of 262 patients with maximal local therapy, 115 met inclusion criteria. Primary definitive treatment was XRT alone in 58% and surgery + XRT in 42%. Median PSA at time of scan was 4.4 ng/mL, and PSMA PET was positive in 87%. First therapy rendered after PSMA PET included 15% no therapy, 26% XRT only, 28% systemic therapy only (ADT +/- NHA), 27% combination therapy (XRT +/- systemic), and 4% other. Subsequent therapy was given in 26%. The median time from first to subsequent therapy was 41 months in patients who received XRT alone as first therapy and not reached for those with combination XRT + ADT. None of the 33 treated with combination therapy required subsequent therapy in 1 year. Remainder of analyses incomplete due to small sample sizes. Results to be updated by time of symposium. Conclusions: This observational study characterizes longer term clinical outcomes in patients with BCR who undergo various therapies after PSMA PET scans. Data may inform current decision making while prospective clinical trial data is awaited.

Metastatic prostate cancer diagnosed by fine-needle aspiration: Contemporary cytopathologic and biomarker assessment with clinical correlates

INTRODUCTION

The diagnosis of metastatic prostatic cancer (MPC) by fine needle aspiration (FNA) can usually be rendered by typical cytomorphologic and immunohistochemical (IHC) features. However, MPC diagnosis may be complicated by transformation to atypical phenotypes such as small cell carcinoma, typically under pressure from androgen deprivation therapy (ADT). Predictive and prognostic biomarkers can also be assessed by IHC. This study illustrates how careful assessment of cytologic and biomarker features may provide therapeutic and prognostic information in MPC.

DESIGN

We reviewed our anatomic pathology archives for MPC diagnosed by FNA from January 2014 to June 2021. Clinical histories, cytology slides, and cell blocks were reviewed. Extensive IHC biomarker workup was performed, including markers of prostate lineage, cell-cycle dysfunction, Ki-67, neuroendocrine markers, PDL1, and androgen receptor splice variant 7. Cases were reclassified into three categories: conventional type, intermediary type, and high-grade neuroendocrine carcinoma (HGNC).

RESULTS

Eighteen patients were identified. Twelve had conventional MPC, including six of six ADT-naive patients. Six of twelve (50%) with prior ADT were reclassified as intermediary or HGNC. Four intermediary cases included two with squamous differentiation and two with pro-proliferative features. Two HGNC cases had typical small cell carcinoma cytomorphology. Expression of PDL1 was identified in two cases and ARv7 in three cases. Five of five intermediary and HGNC patients died of disease versus six of eleven with with conventional type.

CONCLUSIONS

Aggressive cytomorphologic variants were commonly identified in patients with prior ADT. Identification of nonconventional cytomorphology and increased proliferation can provide important prognostic information. Recognition of these changes is important for an accurate diagnosis, and the identification of high-grade variants can affect therapeutic decision-making. Clinically actionable biomarkers such as PDL1 and ARv7 can be assessed by IHC.

Prognostic value of plasma circulating tumor DNA fraction across four common cancer types: a real-world outcomes study

BACKGROUND

Genomic analysis of circulating tumor DNA (ctDNA) is increasingly incorporated into the clinical management of patients with advanced cancer. Beyond tumor profiling, ctDNA analysis also can enable calculation of circulating tumor fraction (TF), which has previously been found to be prognostic. While most prognostic models in metastatic cancer are tumor type specific and require significant patient-level data, quantification of TF in ctDNA has the potential to serve as a pragmatic, tumor-agnostic prognostic tool.

PATIENTS AND METHODS

This study utilized a cohort of patients in a nationwide de-identified clinico-genomic database with metastatic castration-resistant prostate cancer (mCRPC), metastatic breast cancer (mBC), advanced non-small-cell lung cancer (aNSCLC), or metastatic colorectal cancer (mCRC) undergoing liquid biopsy testing as part of routine care. TF was calculated based on single-nucleotide polymorphism aneuploidy across the genome. Clinical, disease, laboratory, and treatment data were captured from the electronic health record. Overall survival (OS) was evaluated by TF level while controlling for relevant covariables.

RESULTS

A total of 1725 patients were included: 198 mCRPC, 402 mBC, 902 aNSCLC, and 223 mCRC. TF ≥10% was highly correlated with OS in univariable analyses for all cancer types: mCRPC [hazard ratio (HR) 3.3, 95% confidence interval (CI) 2.04-5.34, P < 0.001], mBC (HR 2.4, 95% CI 1.71-3.37, P < 0.001), aNSCLC (HR 1.68, 95% CI 1.34-2.1, P < 0.001), and mCRC (HR 2.11, 95% CI 1.39-3.2, P < 0.001). Multivariable assessments of TF had similar point estimates and CIs, suggesting a consistent and independent association with survival. Exploratory analysis showed that TF remained consistently prognostic across a wide range of cutpoints.

CONCLUSIONS

Plasma ctDNA TF is a pragmatic, independent prognostic biomarker across four advanced cancers with potential to guide clinical conversations around expected treatment outcomes. With further prospective validation, ctDNA TF could be incorporated into care paradigms to enable precision escalation and de-escalation of cancer therapy based on patient-level tumor biology.

Satisfaction With Clinician-Led Germline Genetic Counseling in Patients With Prostate Cancer

PURPOSE

Indications for germline testing in prostate cancer patients have expanded substantially over the past decade. With a near-universal shortage of genetic counselors and increasing demand, increased access to genetic counseling is crucial. We sought to prospectively implement and assess a clinician-led approach to genetic counseling and testing.

MATERIALS AND METHODS

Patients with metastatic or localized prostate cancer meeting National Comprehensive Cancer Network® criteria for consideration of genetic testing were offered pre-test genetic counseling by their urologist or medical oncologist as part of their routine clinical care and concurrently approached for enrollment in the Germline Genetics in Prostate Cancer Study. Consented patients filled out a post-counseling survey using validated instruments to assess the quality of counseling. For patients who elected to undergo genetic testing, an additional validated questionnaire was completed following disclosure of results. The primary outcome was the proportion of patients undergoing testing, with a target >60% of patients. The secondary outcome was overall satisfaction with counseling, with a target >85% of patients.

RESULTS

A total of 275 patients enrolled, and 203 patients elected to undergo genetic testing. Post-counseling surveys were obtained from 265 patients, and post-genetic testing surveys were obtained from 132 patients. Patient satisfaction was high, with 98% of patients reporting being satisfied with the overall quality of pre-test counseling, and 74% of patients elected to undergo genetic testing.

CONCLUSIONS

These results support the effectiveness of clinician-led genetic counseling in prostate cancer. With clinician training, this approach can be utilized to expand access to appropriate germline genetic testing.

BRCAAWAY: A randomized phase 2 trial of abiraterone, olaparib, or abiraterone + olaparib in patients with metastatic castration-resistant prostate cancer (mCRPC) with DNA repair defects

5018

Background: The PARP-inhibitor olaparib is approved for mCRPC patients (pts) with deleterious germline or somatic homologous recombination repair gene mutations (HRRm). PARP1 interacts with androgen signaling, and castration-resistant tumor cells exhibit increased PARP1 activity. Preclinically PARP1-inhibition synergizes with androgen receptor (AR) targeted therapy. BRCAAway is a biomarker selected, randomized, open-label, multicenter phase 2 trial evaluating efficacy of targeting AR vs PARP vs combination in first line mCRPC patients with germline and/or somatic HRRm in BRCA1, BRCA2, or ATM. Methods: Eligible mCRPC pts underwent tumor next generation sequencing and germline testing. Pts with inactivating BRCA1, BRCA2 and/or ATM alterations were randomized 1:1:1 to Arm 1 abiraterone (1000 mg daily) + prednisone (5mg bid) (Abi/pred), Arm 2 olaparib (300 mg bid) or Arm 3 olaparib + Abi/pred. The primary end point is progression-free survival (PFS) analyzed using Kaplan-Meier estimates and Cox regression. Secondary endpoints include measurable disease response rate (RR) by RECIST, PSA-RR, undetectable PSA (≤ 0.2 ng/ml) and toxicity. Arms 1 and 2 pts were allowed to cross over at progression. Pts with other HRRm were treated with olaparib; Arm 4 (ongoing). Results: 161 pts were registered and had NGS testing; 60 pts were randomized to Arms 1-3; to date 59 are evaluable for toxicity and 53 are evaluable for PFS. Baseline median age 67 (range 42-85) years; 54 pts were White, 6 were Black; sites of disease: bone only (n=31), soft tissue only (n=18), bone and soft tissue (n=10); median PSA 14.61 ng/ml (range 0.15-4036.8). Mutational status: BRCA1 only n = 2, BRCA2 only n = 39, ATM only n = 8, and > 1 HRRm n = 11. 34 pts had germline and 26 had somatic mutations. Median (range) follow-up time: 8.3 (0.8, 33.3), 12.2 (2.7, 21.8) and 16.8 (2.9, 41.7) months in Arms 1, 2 and 3. 43 pts had treatment-related adverse events; most common were fatigue (23 pts; 1 Grade (G) 3, 22 G1/2), nausea (17 pts, G1/2), and anemia (9 pts, 2 G3, 7 G1/2). ≥50% PSA decline was 79%, 67%, and 85% of pts in Arms 1, 2, and 3, respectively. Median PSA nadir (ng/mL) (95% CI) Arms 1-3: 2.17 (0.44, 49.27), 3.10 (0.83, 12.01), and 0.50 (0.10, 2.13), respectively. Undetectable PSA, median PFS, and 12-month PFS by Arm are listed in the table. Conclusions: In mCRPC pts with inactivating BRCA1, BRCA2 and/or ATM alterations Abi/pred + olaparib was well tolerated and resulted in longer PFS and better PSA response vs either agent alone. Clinical trial information: NCT03012321. [Table: see text]

Focal radiation with pulsed systemic therapy of abiraterone, androgen deprivation therapy (ADT), olaparib towards castration-sensitive oligometastatic prostate cancer (FAALCON Trial)

TPS5113

Background: Molecular imaging (i.e. PSMA directed agents) identifies metastatic prostate cancer at an earlier disease state than conventional imaging resulting in a new clinical entity within metastatic hormone-sensitive prostate cancer (mHSPC): molecular positive HSPC (mpHSPC). Historically, patients in this category with prior local therapy would have been classified as having a biochemical recurrence only, and observation was routine. Approaches to mpHSPC include observation or the use of focal and/or systemic therapies. Focal radiation for mpHSPC may delay the need for systemic therapy, yet many patients require further focal or systemic treatment. Androgen deprivation therapy (ADT) with abiraterone (abi) benefits men with high-risk localized disease and standard mHSPC. mpHSPC hypothetically resides somewhere between these two disease states. Finally, the inhibition of poly(ADP-ribose) polymerase (PARP) with olaparib plus abi shows promise in metastatic castration resistant prostate, suggesting this approach may be worthy of testing in earlier disease states. Methods: FAALCON is a single-site, phase 2 clinical trial testing olaparib with abi, ADT and radiation therapy in oligometastatic mpHSPC. Oligometastatic mpHSPC is defined as up to 5 radiation treatment sites (5 cm maximum size each) and must encompass all visible disease on the molecular scan. Patients must have had their prostate previously treated. The primary endpoint is the percentage of patients without treatment failure 24 months from study start. Treatment failure is defined as one of the following: new or progressive metastases on CT/MRI, new lesions on bone scan without alternate explanation, clinical progression, or a PSA doubling time under 6 months with an absolute final PSA over 1.5 ng/mL. Additional radiation therapy is deemed progression. Select secondary endpoints include time to any subsequent therapy, and percentage of patients with undetectable PSA with a recovered testosterone at multiple timepoints. Correlative work will analyze quality of life and prior prostatic tissue. ADT and abi (1000 mg daily) are given for 6 months, and radiation is completed by day 40. Olaparib (300 mg PO twice daily) is started 2 weeks after radiation completes and continues for the remaining ̃5 months. After therapy completion, patients are monitored by PSA q3 months with imaging based on predetermined PSA cutoffs. Molecular imaging (PSMA-PET) may be offered on study. Historical disease control at 24 months is estimated at 40% from prior molecular guided radiation studies and intermittent ADT. With 80% power and a one-sided 5% type-I error, we can detect a hazard ratio of 0.5 (80% control rate) at 24 months with 26 patients. To account for dropout, 29 patients will be accrued. Clinical trial information: NCT04748042.

Leveraging artificial intelligence to predict ERG gene fusion status in prostate cancer

Background

TMPRSS2-ERG gene rearrangement, the most common E26 transformation specific (ETS) gene fusion within prostate cancer, is known to contribute to the pathogenesis of this disease and carries diagnostic annotations for prostate cancer patients clinically. The ERG rearrangement status in prostatic adenocarcinoma currently cannot be reliably identified from histologic features on H&E-stained slides alone and hence requires ancillary studies such as immunohistochemistry (IHC), fluorescent in situ hybridization (FISH) or next generation sequencing (NGS) for identification.

Methods

Objective

We accordingly sought to develop a deep learning-based algorithm to identify ERG rearrangement status in prostatic adenocarcinoma based on digitized slides of H&E morphology alone.

Design

Setting, and Participants: Whole slide images from 392 in-house and TCGA cases were employed and annotated using QuPath. Image patches of 224 × 224 pixel were exported at 10 ×, 20 ×, and 40 × for input into a deep learning model based on MobileNetV2 convolutional neural network architecture pre-trained on ImageNet. A separate model was trained for each magnification. Training and test datasets consisted of 261 cases and 131 cases, respectively. The output of the model included a prediction of ERG-positive (ERG rearranged) or ERG-negative (ERG not rearranged) status for each input patch.

Outcome measurements and statistical analysis: Various accuracy measurements including area under the curve (AUC) of the receiver operating characteristic (ROC) curves were used to evaluate the deep learning model.

Results and Limitations

All models showed similar ROC curves with AUC results ranging between 0.82 and 0.85. The sensitivity and specificity of these models were 75.0% and 83.1% (20 × model), respectively.

Conclusions

A deep learning-based model can successfully predict ERG rearrangement status in the majority of prostatic adenocarcinomas utilizing only H&E-stained digital slides. Such an artificial intelligence-based model can eliminate the need for using extra tumor tissue to perform ancillary studies in order to assess for ERG gene rearrangement in prostatic adenocarcinoma.

A transcriptomic model for homologous recombination deficiency in prostate cancer

BACKGROUND

Tumors with mutations associated with homologous recombination deficiency (HRD) are uncommon in prostate cancer (PCa) and variably responsive to PARP inhibition. To better identify tumors with HRD, we developed a transcriptomic signature for HRD in PCa (HRD-P).

METHODS

By using an established mutational signature, we created and validated HRD-P in six independent PCa cohorts (primary PCa, n = 8224; metastatic castration-resistant PCa [mCRPC], n = 328). Molecular and clinical features were compared between HRD-P+ tumors and those with single HR-gene mutations.

RESULTS

HRD-P+ tumors were more common than tumors with single HR-gene mutations in primary (201/491, 41% vs 32/491 6.5%) and mCRPC (126/328, 38% vs 82/328, 25%) cases, and HRD-P+ was more predictive of genomic instability suggestive of HRD. HRD-P+ was associated with a shorter time to recurrence following surgery and shorter overall survival in men with mCRPC. In a prospective trial of mCRPC treated with olaparib (n = 10), all three men with HRD-P+ experienced prolonged (>330 days) PSA progression-free survival.

CONCLUSION

These results suggest transcriptomics can identify more patients that harbor phenotypic HRD than single HR-gene mutations and support further exploration of transcriptionally defined HRD tumors perhaps in conjunction with genomic markers for therapeutic application.

Targeting resistant prostate cancer, with or without DNA repair defects, using the combination of ceralasertib (ATR inhibitor) and olaparib (the TRAP trial)

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Background: Men with metastatic, castration resistant prostate cancer (mCRPC) harboring DNA repair defects (̃20%) achieve a radiographic progression free survival of 7.4 months with PARP inhibitors (PARPi). Preclinical studies combining a PARPi (olaparib) and DNA damage checkpoint inhibitor (ATR inhibitor, ceralasertib) show synergy, providing the rationale to test this combination in men with mCRPC, including where single agent olaparib has been shown to be active. Methods: Two cohorts were accrued to a trial combining ceralasertib with olaparib in men a) with or b) without DNA repair defects. All patients progressed on ≥1 prior mCRPC therapy with no prior PARPi or platinum chemotherapy. The primary endpoint was disease response (confirmed PSA decline ≥50% and/or RECIST response), while disease progression was defined per Prostate Cancer Working Group 3 definition. Each cohort is analyzed independently for disease endpoints, while both groups were combined for toxicity assessments. Results: The 12 person DNA repair-deficient (DRDef) cohort allowed patients with germline BRCA2 loss (n = 4), somatic BRCA2 loss (n = 1) and ATM loss (n = 1 germline, n = 5 somatic and n = 1 somatic with unknown germline). 35 men without BRCA2/BRCA1 or ATM genomic loss were accrued to the DNA repair-proficient (DRPro) cohort. These men had next-generation sequencing (NGS) on contemporary biopsies (prior to enrolment without intervening therapy, 12), prior NGS on metastatic tissue (10), prior NGS on primary prostatic tissue (n = 3), or cell-free analyses (5). Five patients have incomplete cell-free analyses. At data cutoff (October 2021), in the DRDef cohort, the response rate by confirmed ≥50% PSA decline was 4/10 (40%) including 3 of 4 BRCA2 patients, and another is awaiting sufficient follow up; 1 of 6 ATM-deficient patients responded and another is awaiting sufficient follow up. All 4 DRDef responders remain on therapy (median of 8 months). For patients in the DRPro cohort who have completed therapy and response assessment (n = 21), 3 responded, one with a duration of 12 months, two with 6 months. An updated analysis will be presented. Conclusions: This analysis suggests potential activity of the doublet for DRDef (BRCA2 mainly) and DRPro mCRPC. Ongoing biomarker analysis (e.g. ATM IHC, contemporaneous cell-free DNA analysis rather than archived tissue) may help guide selection of patients most likely to benefit. Clinical trial information: NCT03787680.

ABLE: Phase 2, single-arm, two-stage study of nabpaclitaxel with anti-PD1/PDL1 in advanced urothelial cancer

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Background: Anti-PD/PDL1 immune checkpoint inhibitor monotherapy is standard in select PDL1 expressing advanced urothelial cancer (aUC) and platinum-refractory aUC. Nab-paclitaxel (NAB) previously showed encouraging activity in platinum-refractory aUC. We conducted a single-arm trial of the combination of NAB and pembrolizumab in platinum-refractory or cisplatin-ineligible aUC. Methods: Eligible patients (pts) had RECIST 1.1 measurable urothelial cancer, grade ≤1 neuropathy, and ECOG PS 0-2. Study therapy consisted of NAB at starting dose of 125 mg/m2 IV on days 1 and 8 and pembrolizumab 200 mg IV on day 1 in 21-day cycles until progression, intolerable toxicity, death, or consent withdrawal. Continuing NAB after 6 cycles was optional. NAB starting dose was reduced to 100 mg/m2 after planned interim analysis on the first 17 subjects. Primary endpoint was overall response rate (ORR) by RECIST 1.1. Secondary endpoints included safety/toxicity, progression free survival (PFS), overall survival, complete response proportion, duration of response (DOR), and duration of therapy (DOT). Results: Between 2/2018 and 4/2021, 36 response evaluable pts were enrolled; 11 of upper tract origin, 32 men, mean age 71.5 years (range 52 – 88), 25 pure urothelial, 15 platinum-refractory, 21 cisplatin-ineligible by Galsky criteria, and ECOG PS was 0, 1 or 2 in 9, 20, and 7 pts, respectively. Unconfirmed best ORR was 58.3% (95% CI: 42-74) including 3 CR and 18 PR, confirmed ORR 50% (18/36); 31/36 pts experienced some tumor shrinkage. Median DOR was 19 weeks (95% CI: 15.6-34.8), and median PFS 5.4 months (95% CI: 4.6-7.9). Pts received a median of 6 cycles (range 1-14) with median DOT 4.2 months (range 0.6-9.6). Grade ≥3 adverse events (AE) occurred in 25 pts including fatigue (n = 6), anemia (n = 6), peripheral neuropathy (n = 3), and oral mucositis (n = 3); 6 discontinued treatment due to AEs. Ten pts had immune mediated AEs including 1 with encephalitis. Archival tumor NGS revealed TMB ≥10 in 5/21 available. Conclusions: The combination of NAB and pembrolizumab exhibited promising activity in advanced urothelial cancer with no unexpected toxicity. Clinical trial information: NCT03240016.

A phase II trial of abemaciclib (abema) and atezolizumab (atezo) in unselected and CDK12-loss metastatic castration-resistant prostate cancer (mCRPC)

TPS213

Background: Alterations in the cell cycle signaling pathway are common in mCRPC and may contribute to resistance to AR-targeted therapies. Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) have revolutionized the therapeutic landscape in ER+ breast cancer and have demonstrated robust anti-tumor activity in multiple pre-clinical mCRPC models such as enzalutamide-resistant cell lines, including those with the androgen-receptor splice variant 7 (AR-V7). Pre-clinical synergy has also been seen in multiple studies of CDK4/6i and anti-programmed death 1 (PD-1) or PD-ligand-1 (PD-L1). Additionally, loss of function alterations of CDK12, found in 5-7% of mCRPC, may confer vulnerability to anti-PD-L1 agents. Methods: This multi-center study will enroll 54 unselected mCRPC patients (pts), randomized 1:1 to abema (arm A) or abema + atezo (arm B); and 21 pts with known loss of function mutations in CDK12 (arm C) treated with atezo (n = 5) or abema + atezo (n = 16). All pts will undergo on-treatment (6-week) tumor biopsy. Treatment will be continued until disease progression and crossover is prohibited. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-1, biopsy-proven prostate adenocarcinoma, progressive metastatic disease per Prostate Cancer Working Group 3 (PCWG3), progression/intolerance to ≥ 1 novel antiandrogen in hormone-sensitive or CRPC setting, ineligible for docetaxel/cabazitaxel (progression within 12 months of taxane, pt refusal, investigator discretion), no uncontrolled comorbidity or history of pneumonitis/ILD. Arms A & B will use two stage design for co-primary endpoints of progression-free survival at 6 months using PCWG3 (6m-PFS) and objective response rate (ORR). If ≥ 1/12 pts meet either co-primary endpoint, 2nd stage will open to enroll 15 more pts in that arm. Treatment will be deemed to have meaningful clinical activity (MCA) if ≥ 6/27 meet 6m-PFS or ≥ 5/27 have an ORR. This will provide 86% power for 6m-PFS (34% vs. 12%) and 85% power for ORR (30% vs. 10%) at a one-sided α = 0.08. For MCA in arm C, 16 patients treated with abema+atezo will provide 80-85% power for 6m-PFS (34% vs. 12%) at a one-sided α = 0.05 using a one-sample log-rank test. Primary safety endpoint is the incidence of dose-limiting toxicities in pts receiving abema+atezo. Key secondary endpoints are clinical benefit rate (ORR + stable disease), duration of response and overall survival in arms A and B, and safety events in all arms. Primary exploratory endpoint is comparison of tumoral FoxP3+/CD8+ ratio in pts treated with abema vs. abema + atezo. Additional exploratory endpoints will evaluate association between response and genomic alterations identified from tissue or circulating tumor-derived exosomes. Enrollment began in July 2021 and projected enrollment goal is 3 years (NCT04751929). Clinical trial information: NCT04751929.

Phase 2 trial of immunotherapy in tumors with CDK12 inactivation (IMPACT): Results from cohort A of patients (pts) with metastatic castration resistant prostate cancer (mCRPC) receiving dual immune checkpoint inhibition (ICI)

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Background: Prostate cancer with CDK12 inactivation represents a distinct subtype in mCRPC, tumors are characterized by excessive tandem duplications, genomic instability, gene fusion-caused putative neoantigens and increased tumor T cell infiltration. Retrospective experiences with ICI in CDK12 inactivation CRPC pts reported PSA and radiographic responses. We conducted a prospective multi-site clinical trial of ipilimumab and nivolumab in CDK12 inactivation or mutated cancers. Herein, we report our findings in the completed cohort A of men with mCPRC. Methods: Eligible pts had mCRPC (ongoing androgen deprivation therapy with serum testosterone £ 50 ng/dL) and putative CDK12 inactivation of function aberrations on any commercial or institutional CLIA/CAP approved next generation sequencing assay. Archival tumor tissue was requested for correlative biomarker analysis. Pts received nivolumab 3 mg/kg IV and ipilimumab 1 mg/kg IV q3 weeks for up to 4 cycles, followed by maintenance nivolumab at 480 mg IV q4 weeks until disease progression, intolerable toxicity, or consent withdrawal. The primary endpoint was PSA response, defined as a greater than or equal to 50% decline in PSA from baseline. Secondary endpoints included safety/toxicity, secondary efficacy measures including QoL and overall survival. Exploratory objectives included baseline tumor whole exome analysis and changes in circulating immune profiles with therapy. Results: As of data cut-off in Aug 2021, 28 mCRPC pts enrolled in Cohort A; median ECOG PS was 1 (0-2 range), 22/28 had Gleason 8-10 cancer, mean baseline PSA at study entry was 231 ng/dL, all pts had received ≥1 prior oral androgen signaling inhibitor and ≥1 cytotoxic chemotherapy. Unconfirmed PSA ≥30% decline was seen in 6/28 pts (21.4%) and PSA ≥50% decline in 4/28 pts (14.2%). Grade ≥3 possible/probable/definite adverse events were noted in 7/28 (25%) and SAEs in 10/28 pts (35.7%). Six pts (21.4%) experienced a rapid PSA increase by ≥ 10-fold over baseline. Conclusions: Combination immunotherapy was reasonably tolerated in this heavily pre-treated population and was associated with unconfirmed PSA responses in a subset of pts. Ongoing correlative analyses could explain responses mechanistically. Enrollment in Cohort B of non-prostate cancers and Cohort C of nivolumab monotherapy in prostate cancer are still ongoing. Clinical trial information: NCT03570619.

A comprehensive assessment of 68Ga-PSMA-11 PET in biochemically recurrent prostate cancer: Results from a prospective multi-center study in 2005 patients

We prospectively investigated the performance of the prostate-specific membrane antigen (PSMA) ligand ⁶⁸Ga-PSMA-11 for detecting prostate adenocarcinoma in patients with elevated prostate-specific-antigen (PSA) after initial therapy. Methods: ⁶⁸Ga-PSMA-11 hybrid positron emission tomography (PET) was performed in 2005 patients at the time of biochemical recurrent prostate cancer (BCR) following either radical prostatectomy (RP) (50.8 %), definitive radiation therapy (RT) (19.7 %), or RP with post-operative RT (PORT) (29.6 %). Presence of prostate cancer was assessed qualitatively (detection rate = positivity rate) and quantitatively on a per-patient and per-region basis creating a disease burden estimate from presence or absence of local (prostate/prostate bed), nodal (N1: pelvis) and distant metastatic (M1: distant soft tissue and bone) disease. The primary study endpoint was the positive predictive value (PPV) of ⁶⁸Ga-PSMA-11 PET/CT confirmed by histopathology. Results: Following prostatectomy, the scan detection rate increased significantly with rising PSA levels (44.8 % at PSA < 0.25 to 96.2 % at PSA > 10 ng/mL; P < 0.001). The detection rate significantly increased with rising PSA levels in each individual region, overall disease burden, prior androgen deprivation, clinical T-stage, and Gleason grading from prostatectomy specimen (P < 0.001). Following RT, the detection rate for in-gland prostate recurrence was 64.0 % compared to 20.6 % prostate bed recurrences after RP and 13.3 % following PORT. PSMA-positive pelvic nodal disease was detected in 42.7 % following RP, in 40.8 % after PORT and 38.8 % after RT. In patients with histopathologic validation the PPV per-patient was 0.82 (146/179). The SUV_max of histologically proven true positive lesions was significantly higher than false positive lesions (median 11.0 (IQR 6.3 - 22.2) vs 5.1 (IQR 2.2 - 7.4) P < 0.001). Conclusion: We confirmed a high PPV of ⁶⁸Ga-PSMA-11 PET in BCR and the PSA level as the main predictor of scan positivity.

Plasma circulating tumor DNA (ctDNA) fraction and real-world overall survival (rwOS) in metastatic castration resistant prostate cancer (mCRPC)

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Background: Assessment of disease burden and severity influences numerous decisions in cancer care yet is not always straightforward. In mCRPC, most patients (pts) have bone-only metastases, for which disease burden quantification by imaging is challenging. Using commercially available assays for comprehensive genomic profiling (CGP), we hypothesized higher levels of ctDNA would associate with worse rwOS in mCRPC. Methods: Pts with mCRPC who received care within Flatiron Health (FH) network between 1/1/2011-6/30/2020 were assessed. Pts had to have FoundationOne Liquid performed ≤60 days prior to initiation of at least one line of therapy (LOT). Clinical characteristics and treatment history were obtained from deidentified, EHR data and linked to genomic data in the FH-Foundation Medicine Clinico-Genomic Database. Univariable and multivariable Cox proportional hazard models were utilized for rwOS comparisons indexed to LOT start, adjusted for LOT, age, and PSA, hemoglobin, alkaline phosphatase, albumin, and recent ECOG status when available. For one pt with two samples, the earlier one was used. Plasma ctDNA levels were quantified using a composite tumor fraction (cTF) measure based on aneuploidy and variant allele fraction (VAF), dichotomized at a previously reported threshold of 10% (Stover et al, JCO, 2018). Association of cTF with rwOS across common solid tumors was then explored in the FH-FMI CGDB for advanced breast cancer (BC), metastatic colorectal cancer (mCRC) and advanced non-small cell lung cancer (aNSCLC). Results: 78 mCRPC pts met criteria with 36 deaths to date. 15 (19%), 19 (24%), 17 (22%) and 27 (35%) samples were respectively obtained prior to first, second, third, or fourth mCRPC LOT, and median PSA was 85.1 ng/mL (IQR: 23.2 – 177). 69/78 (88%) were from community sites. cTF was ≥ 10% in 46/78 samples (60%) and was significantly associated with median PSA (115 vs. 27 ng/mL, p = 0.006) and elevated alk phos (52.2% vs. 12.5%, p < 0.001). Pts with ≥ 10% cTF had significantly worse rwOS (median 6.2 mo vs. not reached, HR: 9.9, 95% CI: 3.0 – 32.4, p < 0.001), which persisted in the multivariable Cox regression (HR: 9.4, 95% CI: 2.4 – 36.4, p = 0.001, n = 65, 13 missing clinical data). Preliminary results in other cancers, adjusted for LOT number only, were consistent with mCRPC; cTF ≥ 10% was associated with a worse rwOS in mBC (n=245, HR: 1.8 CI: 1.1 – 3.0), mCRC (n=107, HR: 2.1 CI: 1.1 – 4.3) and aNSCLC (n=432, HR: 1.8 CI: 1.3 – 2.5). Conclusions: Pretreatment ctDNA level is a prognostic factor in mCRPC in a real-world setting. With prospective validation, cTF may permit identification of high risk pts requiring more aggressive or investigational therapies. This phenomenon may not be unique to mCRPC and could offer similar insights in other cancer types.

Olaparib vs Cabazitaxel in Metastatic Castration-Resistant Prostate Cancer

This comparative effectiveness research compares survival end points and response rates among patients with metastatic castration-resistant prostate cancer (mCRPC) treated with olaparib and cabazitaxel using results from 2 phase 3 randomized clinical trials.

Intermediate clinical endpoints for surrogacy in localised prostate cancer: an aggregate meta-analysis

BACKGROUND

The international Intermediate Clinical Endpoints in Cancer of the Prostate working group has established metastasis-free survival as a surrogate for overall survival in localised prostate cancer based on the findings of 19 predominantly radiotherapy-based trials. We sought to comprehensively assess aggregate trial-level performance of commonly reported intermediate clinical endpoints across all randomised trials in localised prostate cancer.

METHODS

For this meta-analysis, we searched PubMed for all trials in localised or biochemically recurrent prostate cancer published between Jan 1, 1970, and Jan 15, 2020. Eligible trials had to be randomised, therapeutic, reporting overall survival and at least one intermediate clinical endpoint, and with a sample size of at least 70 participants. Trials of metastatic disease were excluded. Intermediate clinical endpoints included biochemical failure, local failure, distant metastases, biochemical failure-free survival, progression-free survival, and metastasis-free survival. Candidacy for surrogacy was assessed using the second condition of the meta-analytical approach (ie, correlation of the treatment effect of the intermediate clinical endpoint and overall survival), using R2 weighted by the inverse variance of the log intermediate clinical endpoint hazard ratio. The intermediate clinical endpoint was deemed to be a surrogate for overall survival if R2 was 0·7 or greater.

FINDINGS

75 trials (53 631 patients) were included in our analysis. Median follow-up was 9·1 years (IQR 5·7-10·6). Biochemical failure (R2 0·38 [95% CI 0·11-0·64]), biochemical failure-free survival (R2 0·12 [0·0030-0·33]), biochemical failure and clinical failure (R2 0·28 [0·0045-0·65]), and local failure (R2 0·085 [0·00-0·37]) correlated poorly with overall survival. Progression-free survival (R2 0·46 [95% CI 0·22-0·67]) showed moderate correlation with overall survival, and metastasis-free survival (R2 0·78 [0·59-0·89]) correlated strongly.

INTERPRETATION

Intermediate clinical endpoints based on biochemical and local failure did not meet the second condition of the meta-analytical approach and are not surrogate endpoints for overall survival in localised prostate cancer. Our findings validate metastasis-free survival as the only identified surrogate endpoint for overall survival to date.

FUNDING

Prostate Cancer Foundation and National Institutes of Health.

Prostate Radiotherapy With Adjuvant Androgen Deprivation Therapy (ADT) Improves Metastasis-Free Survival Compared to Neoadjuvant ADT: An Individual Patient Meta-Analysis

PURPOSE

There remains a lack of clarity regarding the influence of sequencing of androgen deprivation therapy (ADT) and radiotherapy (RT) on outcomes in prostate cancer (PCa). Herein, we evaluate the optimal sequencing of ADT with prostate-directed RT in localized PCa.

METHODS

MEDLINE (1966-2018), Embase (1982-2018), ClinicalTrials.gov, and conference proceedings (1990-2018) were searched to identify randomized trials evaluating the sequencing, but not duration, of ADT with RT. Two randomized phase III trials were identified, and individual patient data were obtained: Ottawa 0101 and NRG Oncology's Radiation Therapy Oncology Group 9413. Ottawa 0101 randomly assigned patients to neoadjuvant or concurrent versus concurrent or adjuvant short-term ADT. Radiation Therapy Oncology Group 9413, a 2 × 2 factorial trial, included a random assignment of neoadjuvant or concurrent versus adjuvant short-term ADT. The neoadjuvant or concurrent ADT arms of both trials were combined into the neoadjuvant group, and the arms receiving adjuvant ADT were combined into the adjuvant group. The primary end point of this meta-analysis was progression-free survival (PFS).

RESULTS

The median follow-up was 14.9 years. Overall, 1,065 patients were included (531 neoadjuvant and 534 adjuvant). PFS was significantly improved in the adjuvant group (15-year PFS, 29% v 36%, hazard ratio [HR], 1.25 [95% CI, 1.07 to 1.47], P = .01). Biochemical failure (subdistribution HR [sHR], 1.37 [95% CI, 1.12 to 1.68], P = .002), distant metastasis (sHR, 1.40 [95% CI, 1.00 to 1.95], P = .04), and metastasis-free survival (HR, 1.17 [95% CI, 1.00 to 1.37], P = .050) were all significantly improved in the adjuvant group. There were no differences in late grade ≥ 3 gastrointestinal (2% v 3%, P = .33) or genitourinary toxicity (5% v 5%, P = .76) between groups.

CONCLUSION

The sequencing of ADT with prostate-directed RT has significant association with long-term PFS and MFS in localized PCa. Our findings favor use of an adjuvant over a neoadjuvant approach, without any increase in long-term toxicity.

Upper Gastrointestinal Bleeding Due to a Duodenal Metastasis from Primary Testicular Squamous Cell Carcinoma

Patient: Male, 57-year-old

Final Diagnosis: Metastatic squamous cell carcinoma

Symptoms: Dizziness • fatigue • melena • testicular mass

Medication: —

Clinical Procedure: Esophagogastroduodenoscopy • surgery and radiotherapy

Specialty: Gastroenterology and Hepatology • Oncology • Surgery • Urology

CDK12-Altered Prostate Cancer: Clinical Features and Therapeutic Outcomes to Standard Systemic Therapies, Poly (ADP-Ribose) Polymerase Inhibitors, and PD-1 Inhibitors

PURPOSE

In prostate cancer, inactivating CDK12 mutations lead to gene fusion-induced neoantigens and possibly sensitivity to immunotherapy. We aimed to clinically, pathologically, and molecularly characterize CDK12-aberrant prostate cancers.

METHODS

We conducted a retrospective multicenter study to identify patients with advanced prostate cancer who harbored somatic loss-of-function CDK12 mutations. We used descriptive statistics to characterize their clinical features and therapeutic outcomes (prostate-specific antigen [PSA] responses, progression-free survival [PFS]) to various systemic therapies, including sensitivity to poly (ADP-ribose) polymerase and PD-1 inhibitors.

RESULTS

Sixty men with at least monoallelic (51.7% biallelic) CDK12 alterations were identified across nine centers. Median age at diagnosis was 60.5 years; 71.7% and 28.3% were white and nonwhite, respectively; 93.3% had Gleason grade group 4-5; 15.4% had ductal/intraductal histology; 53.3% had metastases at diagnosis; and median PSA was 24.0 ng/mL. Of those who underwent primary androgen deprivation therapy for metastatic hormone-sensitive disease (n = 59), 79.7% had a PSA response, and median PFS was 12.3 months. Of those who received first-line abiraterone and enzalutamide for metastatic castration-resistant prostate cancer (mCRPC; n = 34), 41.2% had a PSA response, and median PFS was 5.3 months. Of those who received a first taxane chemotherapy for mCRPC (n = 22), 31.8% had a PSA response, and median PFS was 3.8 months. Eleven men received a PARP inhibitor (olaparib [n = 10], rucaparib [n = 1]), and none had a PSA response (median PFS, 3.6 months). Nine men received a PD-1 inhibitor as fourth- to sixth-line systemic therapy (pembrolizumab [n = 5], nivolumab [n = 4]); 33.3% had a PSA response, and median PFS was 5.4 months.

CONCLUSION

CDK12-altered prostate cancer is an aggressive subtype with poor outcomes to hormonal and taxane therapies as well as to PARP inhibitors. A proportion of these patients may respond favorably to PD-1 inhibitors, which implicates CDK12 deficiency in immunotherapy sensitivity.

Efficacy and Effect of Cabozantinib on Bone Metastases in Treatment-naive Castration-resistant Prostate Cancer

BACKGROUND

Cabozantinib is active in advanced prostate cancer with improvement on bone scans in men on phase II trials. This trial evaluated the efficacy and changes in bone lesions in men with metastatic castration-resistant prostate cancer (mCRPC) treated with cabozantinib.

PATIENTS AND METHODS

Eligible patients with mCRPC involving bone underwent biopsy of a bone lesion followed by cabozantinib starting at 60 mg daily and continuing until progression or intolerable toxicity. The primary study endpoint was progression-free survival at 12 weeks. The bone lesion was rebiopsied at 6 weeks. Expression of CMET, phospho-CMET, and VEGFR2 was assayed by immunohistochemistry. Serum was obtained at baseline, and at 3, 6, and 12 weeks and assayed for bone remodeling markers.

RESULTS

A total of 25 patients were enrolled: 22 were evaluable, and 3 were excluded before receiving cabozantinib. At 12 weeks, 17 (77%) of 22 patients had stable disease or better. The median time on treatment was 24 weeks (range, 3-112 weeks). The overall median progression-free survival was 43.7 weeks (95% confidence interval, 23.7-97.0 weeks). Eight (36%) of 22 patients had markedly reduced uptake on bone scan. Patients with significant response on bone scan had higher bone morphogenic protein-2 levels at baseline, stable N-telopeptides levels, increased vascular endothelial growth factor receptor 2 expression, and a trend towards increased phospho-CMET while on cabozantinib compared with patients with stable disease.

CONCLUSIONS

Cabozantinib is active in men with mCRPC, inducing significant changes on bone scan in one-third of patients with changes in markers of bone formation and the tumor microenvironment.

Targeting resistant prostate cancer with ATR and PARP inhibition (TRAP trial): A phase II study

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Background: Inhibition of poly(ADP-ribose) polymerase (PARP) shows promise in prostate cancer, but is limited to the ~20% of men with defects in genes encoding for DNA repair proteins BRCA1, BRCA2 or ATM (homologous recombination defect positive, HRD+). The effect is modest for HRD+ patients with a progression free survival of ~7 months. Pharmacologically simulating genetic DNA repair defects may expand who benefits to homologous recombination defect negative (HRD-) patients and improve HRD+ response. The ataxia telangiectasia and Rad3-related protein (ATR) is ideal with its roles in cell cycle regulation, replication fork resolution and both single and double strand break repair. Preclinical studies on HRD-/HRD+ cell lines support this. We hypothesize co-inhibition of ATR and PARP will respond regardless of HRD status. Methods: TRAP is a prospective, multi-institutional, phase 2 clinical trial testing AZD6738 combined with olaparib in HRD+ and HRD- mCRPC patients. Primary endpoint is the response rate (RR) by RECIST radiographic response or PSA decline ≥50% in 35 HRD- patients, with a secondary objective of RR in 12 HRD+ patients. HRD+ is mono/biallelic loss of ATM or biallelic loss of BRCA1/2. Tissue based sequencing is done unless completed prior in mCRPC, known BRCA germline loss, treating provider deems biopsy unsafe or biopsy fails. Those unable or failing biopsy are designated as HRD-, but BRCA1/2 and ATM are tested via circulating tumor DNA in a commercial test. Eligible patients must progress after ≥1 line of mCRPC therapy. Progression on a second generation anti-androgen (e.g. apalutamide), abiraterone or within 6 months of docetaxel in hormone sensitive disease are eligible. Treatment entails 160 mg PO daily of AZD6738 on days 1-7 and 300 mg PO BID of olaparib on days 1-28 of a 28-day cycle. Statistical analysis will provide RR with 95% binomial confidence intervals. Analysis of tumor specimens, circulating tumor cells and DNA will be performed for predictors of response and acquired resistance. The study is at four sites in the US, participates in the Prostate Cancer Clinical Trials Consortium, LLC, is managed by the University of Michigan and funded by AstraZeneca. Clinical trial information: NCT03787680.

ABLE: single-arm trial of nab-paclitaxel with ANTI-PD1 in advanced urothelial cancer

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Background: Anti-PD1 immune checkpoint inhibitor monotherapy is standard in cisplatin ineligible advanced urothelial cancer (aUC) patients (pts) that is PDL1 positive as well as in platinum refractory aUC. Nab-paclitaxel (Abraxane) monotherapy showed an overall response rate (ORR) of 27.7% in platinum refractory aUC. We conducted a single-arm trial of nab-paclitaxel and pembrolizumab in platinum refractory or cisplatin ineligible aUC (NCT03240016). Methods: Eligible pts had RECIST 1.1 measurable disease, grade 1 or lower neuropathy and adequate organ function. Study therapy consisted of nab-paclitaxel at starting dose of 125 mg/m2 IV on days 1 and day 8 and pembrolizumab 200 mg IV on day 1 in 21-day cycles until progression, intolerable toxicity, death or consent withdrawal. Primary endpoint was ORR by RECIST 1.1criteria. Secondary endpoints included safety/toxicity, progression free survival, overall survival, complete response proportion, duration of response (DOR) and duration of therapy (DOT). Results: Seventeen pts were enrolled between 02/2018 to 04/2019; 16 were response evaluable. Seven were of upper tract origin, 14/17 men, mean age 70.9 yrs (52 – 83), 71% pure urothelial, 8/17 platinum refractory; 9/17 cisplatin ineligible by Galsky criteria, and ECOG PS was 0, 1 or 2 in 6, 8 and 3 pts respectively. Unconfirmed ORR was 9/16 (56.25%: 95% CI [30-80%]), confirmed in 7; 14 pts experienced some tumor shrinkage; 2 pts had CR and 7 pts PR. Median DOR was 18 wks (95% CI: 6-NR) and median PFS 5.4 m (95% CI: 3.9-5.7). Pts received a median 6 cycles (range 1-11) with median DOT 4.4 m (0.7-7.6). Median follow up was 5.1 m. Grade ≥3 adverse events (AE) occurred in 15/17 pts including fatigue (n=5), peripheral neuropathy (n=3), anemia (n=3) and oral mucositis (n=3). Five pts had immune mediated AEs including 1 encephalitis; 5 pts discontinued treatment due to AEs, all attributed to nab-paclitaxel. Conclusions: The combination of nab-paclitaxel and pembrolizumab in advanced urothelial cancer exhibited promising activity but with moderate toxicity. A follow-up expansion study with nab-paclitaxel starting dose at 100 mg/m2 in 19 additional pts is being initiated. Correlative studies including PD-L1 expression and TILs are underway. Clinical trial information: NCT03240016.

Polypoidal giant cancer cells in metastatic castration-resistant prostate cancer: observations from the Michigan Legacy Tissue Program

Despite early diagnosis and established protocols, a subset of prostate cancer patients will eventually be categorized as castration-resistant prostate cancer. Recently, it has been reported that these multi-modal therapy cases may harbor a special subset of cancer cells termed as polypoidal giant cancer cells (PGCC). These cells are phenotypically described either as possessing highly irregular polylobated nuclei or multiple pleomorphic nuclei. To identify and characterize the distribution of these cells, we created a cohort of 5 randomly selected cases of multi-modal therapy failure prostate cancer (16 selected non-osseous and osseous tumor sites) enrolled in Michigan Legacy Tissue Program. In all cases, specific "regions of interest" or "hot spots" within tumor areas showing an increased proportion of these multi-nucleated/polylobated cells under light microscopy were labeled as PGCC-rich area. On microscopic evaluation, overall mean count of PGCC was 42.4 ± 3.91 with case 2 in the study cohort with the highest number of average PGCC count of 17 ± 4.04. Site wise analysis showed retroperitoneal lymph node as the tissue with highest number of average PGCC number/site (5.0 ± 0.32). On correlating the average number of PGCC recorded with the time elapsed from last dose of chemotherapy administered to autopsy, the spearman correlation value (R) was 0.67, but the result was not statistically significant (p = 0.22). A systematic assessment of PGCC in a large stratified cohort of prostate cancer patients integrated with various histopathological and clinical parameters along with discovery of specific biomarkers for PGCC are the future studies suggested.

Plasmacytoid urothelial carcinoma: a rapid autopsy case report with unique clinicopathologic and genomic profile

Background

Rapid (“warm”) autopsies of patients with advanced metastatic cancer provide important insight into the natural history, pathobiology and histomorphology of disease in treatment-resistant tumors. Plasmacytoid urothelial carcinoma (PUC) is a rare variant of urothelial carcinoma characterized by neoplastic cells morphologically resembling plasma cells. PUC is typically aggressive, high-stage at presentation, and associated with poor outcomes. Recurrence is common in PUC, with the majority of recurrences occurring in the peritoneum.

Case presentation

Here, we report rapid autopsy findings from a patient with recurrent PUC. The patient had persistent pain after cystoprostatectomy, although initial post-operative imaging showed no evidence of disease. Imaging obtained shortly before his death showed only subtle growth along vascular tissue planes; however, extensive disease was seen on autopsy. Plasmacytoid tumor cells formed sheets involving many serosal surfaces. Molecular interrogation confirmed a mutation in CDH1 exon 12 leading to early truncation of the CDH1 protein in the tumor cells.

Conclusions

The sheet-like growth pattern of PUC makes early phases of disease spread much more difficult to capture on cross-sectional imaging. Alternative forms of surveillance may be required for detection of recurrent PUC, and providers may need to treat based on symptoms and clinical suspicion.

BAI1 Suppresses Medulloblastoma Formation by Protecting p53 from Mdm2-Mediated Degradation

Adhesion G protein-coupled receptors (ADGRs) encompass 33 human transmembrane proteins with long N termini involved in cell-cell and cell-matrix interactions. We show the ADGRB1 gene, which encodes Brain-specific angiogenesis inhibitor 1 (BAI1), is epigenetically silenced in medulloblastomas (MBs) through a methyl-CpG binding protein MBD2-dependent mechanism. Knockout of Adgrb1 in mice augments proliferation of cerebellar granule neuron precursors, and leads to accelerated tumor growth in the Ptch1+/- transgenic MB mouse model. BAI1 prevents Mdm2-mediated p53 polyubiquitination, and its loss substantially reduces p53 levels. Reactivation of BAI1/p53 signaling axis by a brain-permeable MBD2 pathway inhibitor suppresses MB growth in vivo. Altogether, our data define BAI1's physiological role in tumorigenesis and directly couple an ADGR to cancer formation.

Multimodal imaging provides insight into targeted therapy response in metastatic prostate cancer to the bone

Metastatic prostate cancer to bone remains incurable, driving efforts to develop individualized, targeted therapies to improve clinical outcomes while limiting adverse side-effects. Due to the complexity in cellular signaling pathways and the interaction between cancer and its microenvironment, multiparametric imaging approaches for treatment response may improve understanding of the biological effects of therapy. An orthotopic model of castration resistant prostate cancer (CRPC) bone metastasis was treated with the tyrosine kinase inhibitor Cabozantinib (CABO). Response was assessed using CT to monitor bone volumes, ^99mTc-MDP SPECT for bone metabolism, and anatomical and diffusion MRI for tumor volume and cell death. A concurrent clinical trial of CABO for CRPC patients also evaluated multimodality imaging in correlation with standard response criteria. Response in the preclinical study found significant slowing in tumor growth rate (P<0.01), rise in tumor apparent diffusion coefficient (ADC, P<0.001), and drop in ^99mTc-MDP adsorption (P<0.05). Loss of bone volume did not slow with treatment, attributed to the highly aggressive and osteolytic nature of the PC3 cell line. Clinical trial analysis found only a single subject who progressed after 12 weeks of therapy. Imaging at 6 weeks corroborated the 12-week radiological assessment with positive response visible as increased ADC and decreased vascular metrics. Conversely, the subject who progressed at 12 weeks had no change in ADC, and substantial drops in vascular metrics. These results showcase a multifaceted translational imaging approach for detecting targeted treatment response with effective blockade of tumor vascularization, tumor cell kill, and reduced proliferation.

PARP1 Trapping and DNA Replication Stress Enhance Radiosensitization with Combined WEE1 and PARP Inhibitors

KRAS mutations in non-small cell lung cancer (NSCLC) cause increased levels of DNA damage and replication stress, suggesting that inhibition of the DNA damage response (DDR) is a promising strategy for radiosensitization of NSCLC. This study investigates the ability of a WEE1 inhibitor (AZD1775) and a PARP inhibitor (olaparib) to radiosensitize KRAS-mutant NSCLC cells and tumors. In addition to inhibiting the DDR, these small-molecule inhibitors of WEE1 and PARP induce DNA replication stress via nucleotide exhaustion and PARP trapping, respectively. As monotherapy, AZD1775 or olaparib alone modestly radiosensitized a panel of KRAS-mutant NSCLC lines. The combination of agents, however, significantly increased radiosensitization. Furthermore, AZD1775-mediated radiosensitization was rescued by nucleotide repletion, suggesting a mechanism involving AZD1775-mediated replication stress. In contrast, radiosensitization by the combination of AZD1775 and olaparib was not rescued by nucleosides. Whereas both veliparib, a PARP inhibitor that does not efficiently trap PARP1 to chromatin, and PARP1 depletion radiosensitized NSCLC cells as effectively as olaparib, which does efficiently trap PARP, only olaparib potentiated AZD1775-mediated radiosensitization. Taken together, these mechanistic data demonstrate that although nucleotide depletion is sufficient for radiosensitization by WEE1 inhibition alone, and inhibition of PARP catalytic activity is sufficient for radiosensitization by olaparib alone, PARP1 trapping is required for enhanced radiosensitization by the combination of WEE1 and PARP inhibitors.Implications: This study highlights DNA replication stress caused by nucleotide depletion and PARP1 trapping as an important mechanism of radiosensitization in KRAS-mutant tumors and supports further development of DNA replication as a therapeutic target. Mol Cancer Res; 16(2); 222-32. ©2017 AACR.

Translation of Targeted Radiation Sensitizers into Clinical Trials

Over the past century, technologic advances have promoted the evolution of radiation therapy into a precise treatment modality allowing for the maximal administration of dose to tumors while sparing normal tissues. Coinciding with this technological maturation, systemic therapies have been combined with radiation in an effort to improve tumor control. Conventional cytotoxic agents have improved survival in several tumor types but cause increased toxicity due to effects on normal tissues. An increased understanding of tumor biology and the radiation response has led to the nomination of several pathways whose targeted inhibition has the potential to radiosensitize tumor cells with lesser effects on normal tissues. These pathways include those regulating the cell cycle, DNA damage repair, and mitogenic signaling. Few drugs targeting these pathways are in clinical practice, although many are in clinical trials. This review will describe the rationale for combining agents targeting these pathways with radiation, provide an overview of the current landscape in the clinical pipeline and attempt to outline the future steps.

Humanizing π-class glutathione S-transferase regulation in a mouse model alters liver toxicity in response to acetaminophen overdose

Background

Glutathione S-transferases (GSTs) metabolize drugs and xenobiotics. Yet despite high protein sequence homology, expression of π-class GSTs, the most abundant of the enzymes, varies significantly between species. In mouse liver, hepatocytes exhibit high mGstp expression, while in human liver, hepatocytes contain little or no hGSTP1 mRNA or hGSTP1 protein. π-class GSTs are known to be critical determinants of liver responses to drugs and toxins: when treated with high doses of acetaminophen, mGstp1/2+/+ mice suffer marked liver damage, while mGstp1/2−/− mice escape liver injury.

Methodology/Principal Findings

To more faithfully model the contribution of π-class GSTs to human liver toxicology, we introduced hGSTP1, with its exons, introns, and flanking sequences, into the germline of mice carrying disrupted mGstp genes. In the resultant hGSTP1+mGstp1/2−/− strain, π-class GSTs were regulated differently than in wild-type mice. In the liver, enzyme expression was restricted to bile duct cells, Kupffer cells, macrophages, and endothelial cells, reminiscent of human liver, while in the prostate, enzyme production was limited to basal epithelial cells, reminiscent of human prostate. The human patterns of hGSTP1 transgene regulation were accompanied by human patterns of DNA methylation, with bisulfite genomic sequencing revealing establishment of an unmethylated CpG island sequence encompassing the gene promoter. Unlike wild-type or mGstp1/2−/− mice, when hGSTP1+mGstp1/2−/− mice were overdosed with acetaminophen, liver tissues showed limited centrilobular necrosis, suggesting that π-class GSTs may be critical determinants of toxin-induced hepatocyte injury even when not expressed by hepatocytes.

Conclusions

By recapitulating human π-class GST expression, hGSTP1+mGstp1/2−/− mice may better model human drug and xenobiotic toxicology.