Synthetic Lethal Targeting of Cyclin Dependent Kinase-12-Deficient Prostate Cancer with PARP Inhibitors.

PURPOSE: CDK12 is a cyclin-dependent kinase (CDK) that is mutated or amplified in multiple cancers. We previously described a subtype of prostate cancer (PC) characterized predominantly by frameshift, loss-of-function mutations in CDK12. This subtype exhibits aggressive clinical features. EXPERIMENTAL DESIGN: Using isogenic PC models generated by CRISPR/Cas9-mediated inactivation of CDK12, we conducted a chemical library screen of ~1800 FDA-approved drugs. We inhibited cyclin K and CDK13 and evaluated the effects on poly ADP-ribose polymerase inhibitor (PARPi) sensitivity. CDK12 truncation and kinase domain mutations were expressed in cell lines to determine effects on PARPi sensitivity. Mice bearing control and CDK12 mutant prostate tumors were treated with rucaparib. Finally, we evaluated prostate specific antigen (PSA) responses in patients with CDK12 mutations treated with rucaparib on the TRITON2 trial. RESULTS: Cancer cells lacking CDK12 are more sensitive to PARPi than isogenic wild-type cells, and sensitivity depends on the degree of CDK12 inhibition. Inhibiting cyclin K, but not CDK13, also led to PARPi sensitivity and suppressed homologous recombination. CDK12 truncation mutants remained sensitive to PARPi, whereas kinase domain mutants exhibited intermediate sensitivity. The PARPi rucaparib suppressed tumor growth in mice bearing CDK12-mutated tumors. Finally, 6 of 11 (55%) PC patients with biallelic CDK12 mutations had reductions in serum PSA levels when treated with rucaparib on the TRITON2 clinical trial. CONCLUSIONS: In PC, sensitivity to PARPi is dependent on the specific type and zygosity of the CDK12 mutation. PARPi monotherapy may have some activity in PC patients with biallelic inactivating CDK12 alterations.

Integrative identification of non-coding regulatory regions driving metastatic prostate cancer.

Large-scale sequencing efforts have been undertaken to understand the mutational landscape of the coding genome. However, the vast majority of variants occur within non-coding genomic regions. We designed an integrative computational and experimental framework to identify recurrently mutated non-coding regulatory regions that drive tumor progression. Applying this framework to sequencing data from a large prostate cancer patient cohort revealed a large set of candidate drivers. We used (1) in silico analyses, (2) massively parallel reporter assays, and (3) in vivo CRISPR interference screens to systematically validate metastatic castration-resistant prostate cancer (mCRPC) drivers. One identified enhancer region, GH22I030351, acts on a bidirectional promoter to simultaneously modulate expression of the U2-associated splicing factor SF3A1 and chromosomal protein CCDC157. SF3A1 and CCDC157 promote tumor growth in vivo. We nominated a number of transcription factors, notably SOX6, to regulate expression of SF3A1 and CCDC157. Our integrative approach enables the systematic detection of non-coding regulatory regions that drive human cancers.

Clinical cell-surface targets in metastatic and primary solid cancers.

Therapies against cell-surface targets (CSTs) represent an emerging treatment class in solid malignancies. However, high-throughput investigations of CST expression across cancer types have been reliant on data sets of mostly primary tumors, despite therapeutic use most commonly in metastatic disease. We identified a total of 818 clinical trials of CST therapies with 78 CSTs. We assembled a data set spanning RNA-seq and microarrays in 7,927 benign samples, 16,866 primary tumor samples, and 6,124 metastatic tumor samples. We also utilized single-cell RNA-seq data from 36 benign tissues and 558 primary and metastatic tumor samples, and matched RNA versus protein expression in 29 benign tissue samples, 1,075 tumor samples, and 942 cell lines. High RNA expression accurately predicted high protein expression across CST therapies in benign tissues, tumor samples, and cell lines. We compared metastatic versus primary tumor expression, identified potential opportunities for repositioning, and matched cell lines to tumor types based on CST and global RNA expression. We evaluated single-cell heterogeneity across tumors, and identified rare normal cell subpopulations that may contribute to toxicity. Finally, we identified combinations of CST therapies for which bispecific approaches could improve tumor specificity. This study helps better define the landscape of CST expression in metastatic and primary cancers.

Bladder-Preserving Trimodality Treatment for High-Grade T1 Bladder Cancer: Results From Phase II Protocol NRG Oncology/RTOG 0926.

PURPOSE: To investigate the use of radiation with radiosensitizing chemotherapy following repeated transurethral resection (trimodality therapy) as an alternative to radical cystectomy in T1 bladder cancer which has failed Bacillus Calmette-Guerin (BCG). PATIENTS AND METHODS: Patients with recurrent T1 bladders who had failed BCG and were recommended to undergo cystectomy were treated with trimodality therapy. The primary end point was 3-year freedom from cystectomy. Secondary end points were distant metastasis at 3 and 5 years, local recurrence, disease-specific and overall survival (OS), and safety. RESULTS: This single-arm phase II study enrolled 37 patients. Efficacy and safety were evaluated in 34 patients after three exclusions. The median follow-up was 5.1 years. The 3-year freedom from cystectomy rate was 88% (lower one-sided 97.5% confidence limit [CI], 72%), meeting the primary study goal. OS at 3 and 5 years was 69% (95% CI, 54 to 85) and 56% (95% CI, 39 to 74), respectively. The distant metastasis rates at 3 and 5 years were 12% (95% CI, 4 to 26) and 19% (95% CI, 7 to 34), respectively. Eight patients died due to urothelial cancer, 12 exhibited local recurrence at 3 years (cumulative incidence: 32%; 95% CI, 17 to 48), 18 experienced grade 3 adverse events, mostly hematological, and one developed grade 4 neutropenia. CONCLUSION: Trimodality therapy is an effective potential alternative to radical cystectomy for recurrent high-grade T1 urothelial cancer of the bladder. At 3 years, 88% of the patients remained free of cystectomy.

Prognostic factors in post-prostatectomy salvage radiotherapy setting with and without hormonotherapy: An individual patient data analysis of randomized trials from ICECaP database.

BACKGROUND: Early salvage radiotherapy (SRT) is the standard of care for biochemical recurrence post-prostatectomy but outcomes are heterogeneous. OBJECTIVE: To develop a risk scoring system based on relevant standard-of-care clinico-pathological prognostic factors for patients treated with SRT with and without hormonal therapy (HT). DESIGN, SETTING, AND PARTICIPANTS: The Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP) database included three randomized trials (Individual patients' data from 1647 subjects) assessing SRT (GETUG-AFU-16; NRG/RTOG-9601, and a subset of EORTC-22911). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Outcomes were clinical progression (CP). metastasis free-survival (MFS) and overall survival (OS). Clinico-pathological factors, including pathological Gleason Score (GS), PSA at SRT start, margin status, persistent PSA post-RP and time from RP to SRT were evaluated by multivariable models stratified by type of treatment. RESULTS AND LIMITATIONS: On multivariable analysis PSA ≥ 0.5 ng/mL at SRT start, GS ≥ 8 and negative margin status were the three strongest prognostic factors. Three prognostic groups defined by number of these risk features (high risk: 2 or 3; intermediate risk: 1 and low risk: 0) were strongly associated with OS, MFS and CP outcomes with SRT alone or with HT. This prognostic group definition was also relevant for patients with persistent PSA post RP and for patients treated < 1 year from RP to SRT and with and without HT. CONCLUSION: A risk score for patients receiving SRT with or without HT, using three standard-of-care clinico-pathological risk factors provides refined prognostic information for individual patient counselling. PATIENT SUMMARY: By using a composite score of pathology grading (Gleason Score), PSA at start of salvage radiation and margin status data, physicians can provide patients with more refined information on the risk of a second relapse after receiving radiation to the prostate bed after a prostatectomy for a rising or persistent PSA, both with and without hormonal therapy.

Delayed definitive management of localized prostate cancer: what do we know?

Delays in the work-up and definitive management of patients with prostate cancer are common, with logistics of additional work-up after initial prostate biopsy, specialist referrals, and psychological reasons being the most common causes of delays. During the COVID-19 pandemic and the subsequent surges, timing of definitive care delivery with surgery or radiotherapy has become a topic of significant concern for patients with prostate cancer and their providers alike. In response, recommendations for the timing of definitive management of prostate cancer with radiotherapy and radical prostatectomy were published but without a detailed rationale for these recommendations. While the COVID-19 pandemic is behind us, patients are always asking the question: "When should I start radiation or undergo surgery?" In the absence of level I evidence specifically addressing this question, we will hereby present a narrative review to summarize the available data on the effect of treatment delays on oncologic outcomes for patients with localized prostate cancer from prospective and retrospective studies.

Integrated analyses highlight interactions between the three-dimensional genome and DNA, RNA and epigenomic alterations in metastatic prostate cancer.

The impact of variations in the three-dimensional structure of the genome has been recognized, but solid cancer tissue studies are limited. Here, we performed integrated deep Hi-C sequencing with matched whole-genome sequencing, whole-genome bisulfite sequencing, 5-hydroxymethylcytosine (5hmC) sequencing and RNA sequencing across a cohort of 80 biopsy samples from patients with metastatic castration-resistant prostate cancer. Dramatic differences were present in gene expression, 5-methylcytosine/5hmC methylation and in structural variation versus mutation rate between A and B (open and closed) chromatin compartments. A subset of tumors exhibited depleted regional chromatin contacts at the AR locus, linked to extrachromosomal circular DNA (ecDNA) and worse response to AR signaling inhibitors. We also identified topological subtypes associated with stark differences in methylation structure, gene expression and prognosis. Our data suggested that DNA interactions may predispose to structural variant formation, exemplified by the recurrent TMPRSS2-ERG fusion. This comprehensive integrated sequencing effort represents a unique clinical tumor resource.

An Atlas of Accessible Chromatin in Advanced Prostate Cancer Reveals the Epigenetic Evolution during Tumor Progression.

Metastatic castration-resistant prostate cancer (mCRPC) is a lethal disease that resists therapy targeting androgen signaling, the primary driver of prostate cancer. mCRPC resists androgen receptor (AR) inhibitors by amplifying AR signaling or by evolving into therapy-resistant subtypes that do not depend on AR. Elucidation of the epigenetic underpinnings of these subtypes could provide important insights into the drivers of therapy resistance. In this study, we produced chromatin accessibility maps linked to the binding of lineage-specific transcription factors (TF) by performing assay for transposase-accessible chromatin sequencing on 70 mCRPC tissue biopsies integrated with transcriptome and whole-genome sequencing. mCRPC had a distinct global chromatin accessibility profile linked to AR function. Analysis of TF occupancy across accessible chromatin revealed 203 TFs associated with mCRPC subtypes. Notably, ZNF263 was identified as a putative prostate cancer TF with a significant impact on gene activity in the double-negative subtype (AR- neuroendocrine-), potentially activating MYC targets. Overall, this analysis of chromatin accessibility in mCRPC provides valuable insights into epigenetic changes that occur during progression to mCRPC. Significance: Integration of a large cohort of transcriptome, whole-genome, and ATAC sequencing characterizes the chromatin accessibility changes in advanced prostate cancer and identifies therapy-resistant prostate cancer subtype-specific transcription factors that modulate oncogenic programs.

Integrative analysis of ultra-deep RNA-seq reveals alternative promoter usage as a mechanism of activating oncogenic programmes during prostate cancer progression.

Transcription factor (TF) proteins regulate gene activity by binding to regulatory regions, most importantly at gene promoters. Many genes have alternative promoters (APs) bound by distinct TFs. The role of differential TF activity at APs during tumour development is poorly understood. Here we show, using deep RNA sequencing in 274 biopsies of benign prostate tissue, localized prostate tumours and metastatic castration-resistant prostate cancer, that AP usage increases as tumours progress and APs are responsible for a disproportionate amount of tumour transcriptional activity. Expression of the androgen receptor (AR), the key driver of prostate tumour activity, is correlated with elevated AP usage. We identified AR, FOXA1 and MYC as potential drivers of AP activation. DNA methylation is a likely mechanism for AP activation during tumour progression and lineage plasticity. Our data suggest that prostate tumours activate APs to magnify the transcriptional impact of tumour drivers, including AR and MYC.

HER2 overexpression in urothelial carcinoma with GATA3 and PPARG copy number gains.

HER2, encoded by the ERBB2 gene, is an important druggable driver of human cancer gaining increasing importance as a therapeutic target in urothelial carcinoma (UC). The genomic underpinnings of HER2 overexpression in ERBB2 nonamplified UC are poorly defined. To address this knowledge gap, we investigated 172 UC tumors from patients treated at the University of California San Francisco, using immunohistochemistry and next-generation sequencing. We found that GATA3 and PPARG copy number gains individually predicted HER2 protein expression independently of ERBB2 amplification. To validate these findings, we interrogated the Memorial Sloan Kettering/The Cancer Genome Atlas (MSK/TCGA) dataset and found that GATA3 and PPARG copy number gains individually predicted ERBB2 mRNA expression independently of ERBB2 amplification. Our findings reveal a potential link between the luminal marker HER2 and the key transcription factors GATA3 and PPARG in UC and highlight the utility of examining GATA3 and PPARG copy number states to identify UC tumors that overexpress HER2 in the absence of ERBB2 amplification. In summary, we found that an increase in copy number of GATA3 and PPARG was independently associated with higher ERBB2 expression in patient samples of UC. This finding provides a potential explanation for HER2 overexpression in UC tumors without ERBB2 amplification and a way to identify these tumors for HER2-targeted therapies.

Corrigendum to "Androgen Deprivation and Radiotherapy with or Without Docetaxel for Localized High-risk Prostat Cancer: Long-term Follow-up from the Randomized NRG Oncology RTOG 0521 Trial" [Eur. Eurol. 84(2) (2023) 156-163].

BACKGROUND: Intensification of therapy may improve outcomes for patients with high-risk localized prostate cancer. OBJECTIVE: To provide long-term follow-up data from phase III RTOG 0521, which compared a combination of androgen deprivation therapy (ADT) + external beam radiation therapy (EBRT) + docetaxel with ADT + EBRT. DESIGN, SETTING, AND PARTICIPANTS: High-risk localized prostate cancer patients (>50% of patients had Gleason 9-10 disease) were prospectively randomized to 2 yr of ADT + EBRT or ADT + EBRT + six cycles of docetaxel. A total of 612 patients were accrued, and 563 were eligible and included in the modified intent-to-treat analysis. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary endpoint was overall survival (OS). Analyses with Cox proportional hazards were performed as prespecified in the protocol; however, there was evidence of nonproportional hazards. Thus, a post hoc analysis was performed using the restricted mean survival time (RMST). The secondary endpoints included biochemical failure, distant metastasis (DM) as detected by conventional imaging, and disease-free survival (DFS). RESULTS AND LIMITATIONS: After 10.4 yr of median follow-up among survivors, the hazard ratio (HR) for OS was 0.89 (90% confidence interval [CI] 0.70-1.14; one-sided log-rank p = 0.22). Survival at 10 yr was 64% for ADT + EBRT and 69% for ADT + EBRT + docetaxel. The RMST at 12 yr was 0.45 yr and not statistically significant (one-sided p = 0.053). No differences were detected in the incidence of DFS (HR = 0.92, 95% CI 0.73-1.14), DM (HR = 0.84, 95% CI 0.73-1.14), or prostate-specific antigen recurrence risk (HR = 0.97, 95% CI 0.74-1.29). Two patients had grade 5 toxicity in the chemotherapy arm and zero patients in the control arm. CONCLUSIONS: After a median follow-up of 10.4 yr among surviving patients, no significant differences are observed in clinical outcomes between the experimental and control arms. These data suggest that docetaxel should not be used for high-risk localized prostate cancer. Additional research may be warranted using novel predictive biomarkers. PATIENT SUMMARY: No significant differences in survival were noted after long-term follow-up for high-risk localized prostate cancer patients in a large prospective trial where patients were treated with androgen deprivation therapy + radiation to the prostate ± docetaxel.

Risk Stratification of Patients with Recurrence After Primary Treatment for Prostate Cancer: A Systematic Review.

BACKGROUND AND OBJECTIVE: Biochemical recurrence (BCR) after primary definitive treatment for prostate cancer (PCa) is a heterogeneous disease state. While BCR is associated with worse oncologic outcomes, risk factors that impact outcomes can vary significantly, necessitating avenues for risk stratification. We sought to identify prognostic risk factors at the time of recurrence after primary radical prostatectomy or radiotherapy, and prior to salvage treatment(s), associated with adverse oncologic outcomes. METHODS: We performed a systematic review of prospective studies in EMBASE, MEDLINE, and ClinicalTrials.gov (from January 1, 2000 to October 16, 2023) according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines (CRD42023466330). We reviewed the factors associated with oncologic outcomes among patients with BCR after primary definitive treatment. KEY FINDINGS AND LIMITATIONS: A total of 37 studies were included (total n = 10 632), 25 after prostatectomy (total n = 9010) and 12 after radiotherapy (total n = 1622). Following recurrence after prostatectomy, factors associated with adverse outcomes include higher pathologic T stage and grade group, negative surgical margins, shorter prostate-specific antigen doubling time (PSADT), higher prostate-specific antigen (PSA) prior to salvage treatment, shorter time to recurrence, the 22-gene tumor RNA signature, and recurrence location on molecular imaging. After recurrence following radiotherapy, factors associated with adverse outcomes include a shorter time to recurrence, and shorter PSADT or higher PSA velocity. Grade group, T stage, and prior short-term hormone therapy (4-6 mo) were not clearly associated with adverse outcomes, although sample size and follow-up were generally limited compared with postprostatectomy data. CONCLUSIONS AND CLINICAL IMPLICATIONS: This work highlights the recommendations and level of evidence for risk stratifying patients with PCa recurrence, and can be used as a benchmark for personalizing salvage treatment based on prognostics.

Prostate-Specific Membrane Antigen PET Response Associates with Metastasis-Free Survival After Stereotactic Ablative Radiation in Oligometastatic Prostate Cancer.

Purpose: Emerging data suggest that metastasis-directed therapy (MDT) improves outcomes in patients with oligometastatic castration-sensitive prostate cancer (omCSPC). Prostate-specific membrane antigen positron emission tomography (PSMA-PET) can detect occult metastatic disease, and PSMA response has been proposed as a biomarker for treatment response. Herein, we identify and validate a PSMA-PET biomarker for metastasis-free survival (MFS) following MDT in omCSPC. Methods and Materials: We performed an international multi-institutional retrospective study of patients with omCSPC, defined as ≤3 lesions, treated with metastasis-directed stereotactic ablative radiation who underwent PSMA-PET/computed tomography (CT) before and after (median, 6.2 months; range, 2.4-10.9 months) treatment. Pre- and post-MDT PSMA-PET/CT maximum standardized uptake value (SUVmax) was measured for all lesions, and PSMA response was defined as the percent change in SUVmax of the least responsive lesion. PSMA response was both evaluated as a continuous variable and dichotomized into PSMA responders, with a complete/partial response (at least a 30% reduction in SUVmax), and PSMA nonresponders, with stable/progressive disease (less than a 30% reduction in SUVmax). PSMA response was correlated with conventional imaging-defined metastasis-free survival (MFS) via Kaplan-Meier and Cox regression analysis. Results: A total of 131 patients with 261 treated metastases were included in the analysis, with a median follow-up of 29 months (IQR, 18.5-41.3 months). After stereotactic ablative radiation, 70.2% of patients were classified as PSMA responders. Multivariable analysis demonstrated that PSMA response as a continuous variable was associated with a significantly worse MFS (hazard ratio = 1.003; 95% CI, 1.001-1.006; P = .016). Patients classified as PSMA responders were found to have a significantly improved median MFS of 39.9 versus 12 months (P = .001) compared with PSMA nonresponders. Our study is limited as it is a retrospective review of a heterogenous population. Conclusions: After stereotactic ablative radiation, PSMA-PET response appears to be a radiographic biomarker that correlates with MFS in omCSPC. This approach holds promise for guiding clinical management of omCSPC and should be validated in a prospective setting.

Expert Perspectives on Controversies in Castration-Sensitive Prostate Cancer Management: Narrative Review and Report of the First US Prostate Cancer Conference Part 1.

Purpose: Castration-sensitive prostate cancer (CSPC) is a complex and heterogeneous condition encompassing a range of clinical presentations. As new approaches have expanded management options, clinicians are left with myriad questions and controversies regarding the optimal individualized management of CSPC. Materials and Methods: The US Prostate Cancer Conference (USPCC) multidisciplinary panel was assembled to address the challenges of prostate cancer management. The first annual USPCC meeting included experts in urology, medical oncology, radiation oncology, and nuclear medicine. USPCC co-chairs and session moderators identified key areas of controversy and uncertainty in prostate cancer management and organized the sessions with multidisciplinary presentations and discussion. Throughout the meeting, experts responded to questions prepared by chairs and moderators to identify areas of agreement and controversy. Results: The USPCC panel discussion and question responses for CSPC-related topics are presented. Key advances in CSPC management endorsed by USPCC experts included the development and clinical utilization of gene expression classifiers and artificial intelligence (AI) models for risk stratification and treatment selection in specific patient populations, the use of advanced imaging modalities in patients with clinically localized unfavorable intermediate or high-risk disease and those with biochemical recurrence, recommendations of doublet or triplet therapy for metastatic CSPC (mCSPC), and consideration of prostate and/or metastasis-directed radiation therapy in select patients with mCSPC. Conclusions: CSPC is a diverse disease with many therapeutic options and the potential for adverse outcomes associated with either undertreatment or overtreatment. Future studies are needed to validate and clinically integrate novel technologies, including genomics, AI, and advanced imaging, to optimize outcomes among patients with CSPC.

Expert Perspectives on Controversies in Metastatic Castration-Resistant Prostate Cancer Management: Narrative Review and Report of the First US Prostate Cancer Conference Part 2.

Background: Management strategies for metastatic castration-resistant prostate cancer (mCRPC) have rapidly shifted in recent years. As novel imaging and therapeutic approaches have made their way to the clinic, providers are encountering increasingly challenging clinical scenarios, with limited guidance from the current literature. Materials and Methods: The US Prostate Cancer Conference (USPCC) is a multidisciplinary meeting of prostate cancer experts intended to address the many challenges of prostate cancer management. At the first annual USPCC meeting, areas of controversy and consensus were identified during a 2-day meeting that included expert presentations, full-panel discussions, and postdiscussion responses to questions developed by the USPCC cochairs and session moderators. Results: This narrative review covers the USPCC expert discussion and perspectives relevant to mCRPC, including neuroendocrine/aggressive-variant prostate cancer (NEPC/AVPC). Areas of broad agreement identified among USPCC experts include the benefits of poly (ADP-ribose) polymerase (PARP) inhibitors for patients with BRCA1/2 mutations, the use of radioligand therapy in patients with prostate-specific membrane antigen (PSMA)-positive mCRPC, and the need for clinical trials that address real-world clinical questions, including the performance of novel therapies when compared with modern standard-of-care treatment. Ongoing areas of controversy and uncertainty included the appropriateness of PARP inhibitors in patients with non-BRCA1/2 mutations, the optimal definition of PSMA positivity, and systemic therapies for patients with NEPC/AVPC after progression on platinum-based therapies. Conclusions: The first annual USPCC meeting identified several areas of controversy in the management of mCRPC, highlighting the urgent need for clinical trials designed to facilitate treatment selection and sequencing in this heterogeneous disease state.

Assessing Response to PSMA Radiopharmaceutical Therapies with Single SPECT Imaging at 24 Hours After Injection.

Understanding the relationship between lesion-absorbed dose and tumor response in 177Lu-PSMA-617 radiopharmaceutical therapies (RPTs) remains complex. We aimed to investigate whether baseline lesion-absorbed dose can predict lesion-based responses and to explore the connection between lesion-absorbed dose and prostate-specific antigen (PSA) response. Methods: In this retrospective study, we evaluated 50 patients with 335 index lesions undergoing 177Lu-PSMA-617 RPT, who had dosimetry analysis performed on SPECT/CT at 24 h after cycles 1 and 2. First, we identified the index lesions for each patient and measured the lesion-based absorbed doses. Lesion-based response was calculated after cycle 2. Additionally, PSA50 response (a decline of 50% from baseline PSA) after cycle 2 was also calculated. The respective responses for mean and maximum absorbed doses and prostate-specific membrane antigen (PSMA) volumetric intensity product (VIP-PSMA) at cycles 1 and 2 were termed SPECTmean, SPECTmaximum, and SPECTVIP-PSMA, respectively. Results: Of the 50 patients reviewed, 46% achieved a PSA50 response after cycle 2. Of the 335 index lesions, 58% were osseous, 32% were lymph nodes, and 10% were soft-tissue metastatic lesions. The SPECT lesion-based responses were higher in PSA responders than in nonresponders (SPECTmean response of 46.8% ± 26.1% vs. 26.2% ± 24.5%, P = 0.007; SPECTmaximum response of 45% ± 25.1% vs. 19% ± 27.0%, P = 0.001; SPECTVIP-PSMA response of 49.2% ± 30.3% vs. 14% ± 34.7%, P = 0.0005). An association was observed between PSA response and SPECTVIP-PSMA response (R 2 = 0.40 and P < 0.0001). A limited relationship was found between baseline absorbed dose measured with a 24-h single time point and SPECT lesion-based response (R 2 = 0.05, P = 0.001, and R 2 = 0.03, P = 0.007, for mean and maximum absorbed doses, respectively). Conclusion: In this retrospective study, quantitative lesion-based response correlated with patient-level PSA response. We observed a limited relationship between baseline absorbed dose and lesion-based responses. Most of the variance in response remains unexplained solely by baseline absorbed dose. Establishment of a dose-response relationship in RPT with a single time point at 24 h presented some limitations.

Challenges and Opportunities in Establishing Appropriate Intermediate Endpoints Reflecting Patient Benefit: A Roadmap for Research and Clinical Application in Nonmetastatic Prostate Cancer.

Defining meaningful endpoints for research of early-stage high-risk prostate cancer is challenging, with established measures such as overall survival and metastasis-free survival facing limitations related to feasibility and adequate reflection of patient relevance. Developing endpoints must cater to diverse perspectives across scientific, clinical, regulatory, and patient viewpoints. Endpoints such as pathological complete response, no evidence of disease, and prevention of prostate-specific antigen relapse may reflect patient benefit by accounting for diagnostic and treatment burdens.

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 four cycles, followed by nivolumab 480 mg every 4 weeks. Cohort C received nivolumab alone 480 mg every 4 weeks. Patients with CDK12-altered nonprostate tumors were enrolled in cohort B and not reported. The primary endpoint was a 50% reduction in PSA (PSA50). Key secondary endpoints included PSA progression-free survival, overall survival, objective response rate, and safety. RESULTS: PSA was evaluable in 23 patients in cohort A and 14 in cohort C. Median lines of prior therapy were two 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% confidence interval (CI), 1%-28%] in cohort A with two responders; neither had microsatellite instability or a tumor mutational burden >10 mutations/megabase. No PSA50 responses occurred in cohort C. Median PSA progression-free survival 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 overall survival 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.