Management of prostate cancer has improved over the past two decades, driven by innovations in detection of metastatic disease, biomarker characterization, and treatment. This review summarizes the latest progress in managing advanced states of this disease, spanning high risk biochemical recurrence, metastatic hormone sensitive prostate cancer (mHSPC), and metastatic castration resistant prostate cancer (mCRPC). Improved outcomes for patients have been seen with earlier use of androgen receptor pathway inhibitors in the setting of high risk biochemical recurrence and mHSPC. Meanwhile, individuals with mCRPC now represent a more diverse population, differentiated by both their previous treatments and other biological features. Advanced imaging and genomic biomarkers improve patient selection and permit more personalized therapy. Landmark clinical trials and meta-analyses have established and/or refined the role of chemotherapy, poly-ADP ribose polymerase (PARP) inhibitors, and 177Lu-PSMA-617 in this disease space. Finally, as patients with prostate cancer are living longer, the review focuses on understanding and managing potential adverse events, including cardiac and hematologic toxicity and bone health.

Abstract Introduction: Long intergenic noncoding RNAs (lincRNAs) and circular (circ) RNAs have been shown to play key roles in carcinogenesis and tumor progression. Urine represents a promising source of tumor-reflective signals shed directly from the urothelial microenvironment in bladder cancer (BC) patients. Here, we evaluate the urine cell-free (cf) RNA transcriptome in a cohort of 50 patients with localized BC. Methods: A total of 50 localized BC patients and 24 healthy adults were enrolled. Pre-operative urine (collected on the day of radical cystectomy) was processed to isolate cfRNA from urine supernatant. Libraries were prepared using an Illumina tagmentation-based RNA enrichment workflow and sequenced to 100M paired-end reads per sample on a NovaSeq X. FASTQ files were concatenated per sample and QC-checked with RNA-SeQC and Samtools. Reads were aligned to GRCh38/hg38 with STAR, and gene counts were generated using Feature Counts. Linear differential expression analysis (DEA) was performed with DESeq2. For discovery we used random halves of TCGA-BLCA and healthy urine cfRNA samples, alongside a second DEA with random halves of urine BC cfRNA vs. controls; overlapping upregulated genes were validated in the remaining samples. For circular (circ) RNAs, annotations from MiOncoCirc were used; junctions with ≥5 supporting reads were retained, and DEA was conducted with edgeR. Results: In this study, the median age was 68 years, and 80% (40/50) were male. Among the cohort, 66% (33/50) had muscle-invasive bladder cancer (MIBC), of whom 54% received neoadjuvant chemotherapy. Differential expression analysis of TCGA-BLCA tumors and BC urine cfRNA, identified 27 genes commonly upregulated, with 23 of the 27 shared genes strikingly being long intergenic noncoding RNAs (lincRNAs). These BC/urine-specific lincRNAs—including LINC00930, LINC01004, DLG5-AS1, APTR, PSORS1C3, and SERPINB9P1—have known roles in proliferation, EMT, metabolism, and immune signaling. Outside of lincRNAs, tumor-reflective coding transcripts in BC/urine were enriched for autophagy, driven by MAP1LC3B2.TCGA-BLCA survival analysis showed that LINC00930 and PSORS1C3 were associated with worse overall survival. Expanding beyond linear RNA sequences, analysis of urine circRNAs from BC patients revealed a strong cancer-specific dysregulation pattern, with 77 circRNAs significantly upregulated compared with healthy controls. Upregulated urine circRNAs arose from host genes involved in BC-relevant pathways, including invasion (DOCK1, ARHGAP5), autophagy/ER stress (VMP1, ERN1), and luminal differentiation (GRHL2, ESRP1). Conclusion: Cell-free RNA profiling reveals a distinct transcriptomic signature including differential lincRNA- and circRNA-driven autophagy, EMT, proliferation, metabolic, differentiation, and immune signaling programs in the urine of bladder cancer patients. Citation Format: Pradeep Chauhan, Li Lin, Irfan Alahi, Jessica Linford, Lilli J. Greiner, Ayesha Hashmi, Anushka Viswanathan, Nathan Colon, Faridi Qaium, Peter K. Harris, John Sheng, Jacob J. Orme, Eric H. Kim, Zachary L. Smith, Woodson Smelser, Christopher A. Maher, Aadel A. Chaudhuri. Urine cell-free RNA captures tumor-reflective long intergenic noncoding and circular RNA programs in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1133.

Pleomorphic giant cell carcinoma (PGCC) of the prostate is an extremely rare and aggressive malignancy with limited treatment options. We present a case report of metastatic PGCC patients treated with 177Lu-PSMA-617 radioligand therapy (Pluvicto) after progression on standard therapies. Both patients had PSMA-avid tumors on imaging. Molecular profiling revealed mutations in hallmark tumor suppressors including TP53, RB1, and PTEN. Both patients initially experienced partial radiographic response, in which one patient achieved stable disease for 9 months posttherapy. These findings suggest that PSMA-radioligand therapy may be a reasonable treatment for PGCC patients, but underscore the need for additional therapeutic options.

Urothelial carcinoma (UC) with squamous divergent differentiation and pure squamous cell carcinoma (SCC) are aggressive subtypes with limited prospective data on enfortumab vedotin plus pembrolizumab (EV/Pembro). We evaluated outcomes and exploratory correlates. We conducted a retrospective cohort study of adults with pure SCC or UC with squamous divergent differentiation treated with EV/Pembro across Mayo Clinic sites. Best overall response was retrospectively adjudicated from heterogeneous routine-care CT, MRI, and PET reports rather than through uniform prospective RECIST 1.1 assessment. Overall survival (OS), progression-free survival (PFS), duration of response (DoR), and factors associated with OS were evaluated. Forty-nine patients were included; 35 (71.4

PurposeRadioligand therapy (RLT) with [177Lu] Lu-PSMA-617 has shown significant benefits in metastatic castration-resistant prostate cancer (mCRPC), including prolonged overall survival (OS) and progression-free survival (PFS), as well as improved quality of life. For patients previously treated with [177Lu]Lu-PSMA-617 who subsequently experience disease progression, retreatment with [177Lu] Lu-PSMA-617 has emerged as a potential approach, yet data on the outcomes of RLT retreatment remains limited. This study aimed to assess the efficacy and safety of retreatment RLT in mCRPC.MethodsClinical and imaging data of patients who underwent at least two cycles of [177Lu] Lu-PSMA-617, followed by a second course of treatment with [177Lu] Lu-PSMA-617 between March 2018 and December 2024, were retrospectively reviewed. Endpoints included biochemical response, imaging response, toxicity, PSA-PFS, rPFS, and OS. Radiologic and biochemical responses were evaluated using RECIST 1.1 criteria and PSA levels, respectively.ResultsA total of 589 patients underwent [177Lu] Lu-PSMA-617 RLT, of whom 20 (3.4%, 20/589) received RLT retreatment. The median age was 71.3 years (range: 63.7–95.2), and the median follow-up was 73.3 months (95% CI, 35.7–77.2 months) after the initial treatment and 21.7 months (95% CI, 16.9–26.0 months) after retreatment. The initial treatment involved a median of 4.5 cycles (range: 2–6). Following the first course of RLT, 15 patients (75%, 15/20) had exhibited a >50% decline in PSA levels, including 9 who achieved a >90% decrease. Additionally, 12 patients (60%, 12/20) had demonstrated a complete or partial imaging response, while 3 (15%, 3/20) patients had stable disease, and 5 (25%, 5/20) patients had progressive radiologic disease. Patients received a median of 4 retreatment cycles (range, 1–6), and the median interval between initial RLT and retreatment RLT was 33.1 months (IQR, 16.2–48.9 months; range, 10.7–58.8 months). A PSA decline of ≥50% was observed in 9 out of 20 patients (45%, 9/20). An imaging response was observed in 10 patients (50%, 10/20), with 4 achieving a complete response and 6 achieving a partial response, whereas 10 patients (50%, 10/20) showed progression. The median PSA-PFS was 9.8 months (95% CI, 4.1–17.9 months), and the median rPFS was 8.2 months (95% CI, 3.3–17.9 months). Eight deaths occurred during follow-up. The estimated Kaplan Meier OS rates were 83.6% at 12 months (95% CI, 57.3%–94.4%) and 53.7% at 24 months (95% CI, 28.3%–73.7%). Grade 2 renal toxicity was observed in one patient (5%, 1/20). Three patients (15%, 3/20) developed Grade 2 anemia. Notably, no grade 3 or grade 4 adverse events were observed during either treatment period.ConclusionIn our cohort, retreatment with [¹77Lu]Lu-PSMA-617 RLT was associated with biochemical and imaging responses in some patients, with observed survival outcomes that support further investigation. However, given the retrospective single-arm design and small sample size, large prospective studies are needed to more rigorously evaluate the safety, efficacy, and optimal patient selection for retreatment RLT.

Aim: Despite advances with immune checkpoint inhibitor (ICI)-based regimens in the past decade, patients with metastatic urothelial cancer (mUC) face a poor prognosis with few approved options. Platinum-based chemotherapy with paclitaxel and carboplatin (TC) +/– ICI may be a feasible choice. Methods: We generated an IRB-approved, HIPAA-compliant retrospective database of patients at Mayo Clinic Cancer Center with mUC who started TC +/– ICI after disease progression on ICI from January 2018 through December 2024. Baseline demographics, clinicopathologic features, and treatment outcomes were extracted from the electronic health record. Kaplan-Meier method was used to calculate median duration of response (DOR), progression-free survival (PFS) and overall survival (OS). Results: There were 32 patients who fit inclusion criteria, including 31 patients who had disease progression on ICI in the metastatic setting and 1 patient who developed metastatic disease on adjuvant nivolumab. Patients received a median of 4 cycles (range 1–14) of TC over median 12 weeks (range 3–53). Overall, 81% of patients received TC concurrently with an ICI, and 28% continued maintenance ICI after TC discontinuation (at the treating oncologist’s discretion due to adequate response or toxicity). The best objective response rate was 41% and disease control rate was 75%, with median DOR of 4.8 months (IQR 2.7–10.4), median PFS of 4.6 months (IQR 3.3–10.2), and median OS of 9.4 months (IQR 6.3–15.9). Some patients in this series had very durable responses with PFS > 12 months and OS > 24 months. TC +/– ICI was overall well tolerated with expected type and severity of adverse events. Conclusions: Strategies to overcome ICI resistance are needed, and TC +/– ICI after disease progression on an ICI shows promising tolerability and efficacy in this setting for patients with mUC. Our series was notable for some patients having a durable response. Validation in larger cohorts is warranted.

Non-muscle-invasive bladder cancer (NMIBC) comprises approximately 75% of new bladder cancer cases and generally carries a favorable prognosis, yet high rates of recurrence and progression necessitate close surveillance with frequent cystoscopies and repeated transurethral resections. Upfront treatment for high-risk disease is typically Bacillus Calmette-Guérin (BCG), although combinations with immune checkpoint inhibitors have reported results. Patients with BCG-unresponsive, intolerant, or refractory disease represent a subset of patients with high risk of progression, with early radical cystectomy being the standard approach for this setting. Global BCG shortages and the substantial impact of cystectomy on quality of life underscore the need for therapeutic alternatives. Over the past decade, investigational trials in immunotherapy have expanded treatment options for BCG-unresponsive NMIBC with CIS, leading to FDA approval of intravesical nadofaragene firadenovec, nogapendekin alfa-inbakicept, and systemic pembrolizumab. This narrative review summarizes developments in intravesical and systemic immunotherapies for NMIBC, highlights ongoing trials, and addresses controversies in trial design, treatment sequencing, comparative efficacy, and safety.

BACKGROUND:[177Lu]Lu-PSMA-617 (LuPSMA) improves survival and quality of life in men with metastatic castration-resistant prostate cancer but requires substantial healthcare involvement. Our analysis evaluated the time toxicity associated with LuPSMA, representing the first dedicated radioligand time toxicity assessment. MATERIALS AND METHODS:We conducted a multi-institutional retrospective study of patients initiating LuPSMA between April 2022 and March 2023. Patients were followed from first LuPSMA administration until 3 months after the final cycle, initiation of new systemic therapy, or death. Time toxicity was quantified as healthcare contact days during the at-risk interval. Associations with baseline characteristics were evaluated using negative binomial regression models. Univariate and multivariable models were performed. RESULTS:The median age of 135 patients included in the study was 69 years, and the median prior systemic therapies was 4. Patients completed a median of 5 LuPSMA cycles over 7.6 months. Median healthcare contact days were 20 (IQR, 15-28), representing 9.5% (IQR, 6.4-13.9) of at-risk days. Fifteen patients (11%) experienced high time toxicity (>1 contact day per 5 days), while 42 (31%) had low time toxicity (≤1 contact day per 14 days). Among the 57 patients who received both cycle 1 and cycle 6, the mean per cycle healthcare contact days were 4 and 3.6, respectively (paired Wilcoxon signed-rank test, P = .04). Routine oncology visits comprised 32.7% of contact days, compared with 8.8% from hospitalizations. Lower baseline hemoglobin was independently associated with greater time toxicity (RR = 0.87; 95% CI, 0.79-0.96; P = .004). CONCLUSION:In heavily pretreated patients, LuPSMA demonstrated relatively low time toxicity, supporting it as a time-efficient therapy.

Abstract Approximately 288,000 men are diagnosed with prostate cancer (PCa) in the United States each year, with cases expected to double by 2040. While metastatic PCa can be treated with androgen deprivation therapy (ADT) and AR pathway inhibitors (ARPI), it inevitably develops into treatment resistant, lethal disease. The most common ARPI resistance mechanism in PCa is the expression of AR splice variant AR-V7 that lacks the ligand binding domain and is constitutively active. Patients with PCa expressing AR-V7 experience inferior overall survival. Speckle-type POZ protein (SPOP) is an adaptor protein of the Cullin3-based E3 ubiquitin ligase that facilitates both degradative and non-degradative polyubiquitination of targets such as AR. Loss-of-function SPOP mutations occur in approximately 10-15% of prostate cancers, and SPOP-mutant PCa is a unique subtype that has been shown to be exquisitely sensitive to ADT and ARPI treatment. This sensitivity is mediated in part by increased androgen availability via upregulation of hydroxysteroid 17-beta dehydrogenase 4 (HSD17B4) and related steroid synthesis pathways, reduced AR degradation, and enhanced AR cofactor activity. The remarkable efficacy of ARPI in ADT-resistant SPOP-mutant prostate cancer is not well understood. We hypothesized a novel mechanism by which wild-type SPOP promotes AR-V7-mediated resistance to ARPI in PCa. This mechanism may explain the exceptional ARPI sensitivity of SPOP-mutant PCa, distinct from its susceptibility to ADT. We further proposed that clinical SPOP inhibition may broaden this enhanced ARPI susceptibility to the 85-90% of PCa expressing wild-type SPOP. Our results show that SPOP drives ARPI resistance in prostate cancer that can be reversed by SPOP inhibitor. Bulk RNA sequencing showed that SPOP inhibitor targets spliceosome machinery and more importantly, abrogated AR-V7 expression both at transcriptional and protein level. Further investigation revealed that wild-type SPOP ubiquitinates spliceosome regulator SFPQ, promoting AR-V7 alternative splicing and ARPI resistance. While SPOP loss is pathogenic in PCa, leveraging the weakness conferred by SPOP mutation in the 85% of patients with SPOP-wild type provides an innovative strategy to sensitize ARPI resistant disease to standard of care treatment and save lives. Citation Format: Joanina K. Gicobi, Susanna M. Gregory, Nicole A. Becker, Elizabeth A. Bering, Jacob J. Orme.. SPOP drives AR-V7-mediated ARPI resistance in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3904.

Immunotherapy has been effective in many cancer types but has failed in multiple clinical trials in prostate cancers, with the underlying mechanisms remaining largely unclear. Here, we demonstrate that androgen receptor pathway inhibitor (ARPI) plus irradiation (IR) triggered robust anticancer immunity in prostate cancers in both patients and mice. We show that androgen-activated AR suppressed innate immune signaling by inducing inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKBKE) gene repression through HDAC2 interaction with an IKBKE enhancer RNA (IKBKE eRNA, or IKBKE-e). ARPI treatment caused IKBKE derepression and enhanced an IR-induced innate immune response via action of RIG-I and MDA5 dsRNA sensors. IKBKE-e ablation largely enhanced innate immunity in prostate cancer cells in culture and anticancer immunity in mice. Our results revealed AR, HDAC2, and IKBKE eRNA as critical intrinsic immune suppressors in prostate cancer cells, suggesting that rejuvenating inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKKε) signaling by targeting IKBKE-e is an actionable strategy to elicit synthetic anticancer immunity in immunologically "cold" cancers such as prostate cancer.

BACKGROUND:The optimal management of biochemical recurrence (BCR) after radical prostatectomy (RP) remains controversial, particularly in the absence of clinical or radiographic evidence of disease. Salvage radiotherapy (SRT) remains standard of care, but it is unclear whether SRT benefits patients when modern imaging with a multiparametric magnetic resonance imaging (mpMRI) and prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA-PET/CT) are negative for local recurrence. Retrospective data comparing SRT to observation for such patients is fraught with selection bias, underscoring the need for a prospective randomised controlled trial. STUDY DESIGN AND METHODS:The Biochemical Recurrence Irradiation or Observation (BRIO) is a randomised study under the DIVINE trial framework (NCT06378866) enrolling men with BCR (prostate-specific antigen [PSA] level ≥0.2, up to 1.5 ng/mL) after RP with no radiographic evidence of recurrence on mpMRI and PSMA-PET/CT. Major inclusion criteria include age ≥18 years, biochemically recurrent prostate cancer after RP with a PSA level between 0.2 and 1.5 ng/mL, and no local or metastatic recurrence on imaging. A total of 312 patients will be enrolled. Participants are randomised 1:1 to standard-of-care SRT followed by surveillance (Group A), or initial observation with subsequent image-guided therapy at radiographic progression (Group B). Based on historical analysis, a total of 30 metastasis events provides 80% power to detect a significant improvement (hazard ratio 0.5 corresponding to a 5-year metastasis-free proportion of 80.7% in the control group and 89.8% in the experimental group with one-sided type I error rate of 0.15). All participants undergo baseline blood collection to measure prostate cancer-extracellular vesicles and cell-free DNA for biomarker development. Participants are followed in a 16-week cycle with serial PSA measurements, repeat imaging if PSA doubles, safety assessment, and patient-reported outcomes. ENDPOINTS:The primary endpoint is distant recurrence-free survival at 5-years using a 12-month landmark to mitigate bias arising from differing assessment schedules for patients receiving optional 6 months of androgen deprivation therapy. Key secondary outcomes include time to hormone therapy, quality of life measures, adverse effects, and novel blood and urine biomarkers. CONCLUSION:The BRIO study will clarify the clinical benefit of immediate SRT vs observation with image-guided intervention in mpMRI and PET-negative BCR after RP.

In this study, we aimed to identify oncofetal antigens expressed in prostate cancer and systematically examine their potential role using theranostic approaches. Cell surface oncofetal antigens are expressed to a limited extent in adult cells and may be variably expressed in tumor cells. The fact that oncofetal proteins are not expressed in healthy cells minimizes the risk of systemic toxicity, especially when using targeted therapies. Cell surface oncofetal proteins identified in prostate cancer are CEACAM5, Trop-2 (TACSTD2), Glypican-3 (GPC3), ROR1 (NTRKR1), and 5T4 (TPBG). In accordance with PRISMA guidelines, we conducted a systematic review of peer-reviewed articles indexed in Scopus, PubMed and Web of Science databases until February 10, 2025. Studies evaluating the expression, biological role, and therapeutic relevance of cell surface oncofetal antigens in PC were included. Data extraction focused on their functional role in prostate cancer, associated radiopharmaceuticals, and clinical or preclinical therapeutic strategies. Five key oncofetal proteins: CEACAM5, Trop-2, ROR1, GPC3, and 5T4 have been consistently identified in the literature. These proteins have been associated with aggressive PC subtypes, including neuroendocrine and castration-resistant forms; and are linked to key signaling pathways such as Wnt/β-Catenin, EMT, and PI3K/AKT. Several investigational agents targeting these antigens, including antibody-drug conjugates (ADCs), CAR-T cells and radiolabeled imaging probes (e.g. 68Ga, 89Zr, 64Cu, 225Ac) are being developed and evaluated in both preclinical and early clinical settings. CEACAM5, Trop-2, 5T4, GPC3, and ROR1 oncofetal proteins are variably expressed in advanced prostate cancer. Therapeutics and radiopharmaceutical imaging agents targeting these proteins are in development. Though provocative findings are apparent, considerable clinical research is needed to determine the value of targeting these proteins.

The introduction of antibody-drug-conjugates (ADC) that target HER2 has renewed interest in ERBB2 alterations in bladder cancer. Little is known about the frequency of ERBB2 copy number alterations in primary bladder cancer subtypes and regional nodal metastases, and the effect of amplification on protein expression. The objective of this study was to determine the frequency of ERBB2 copy number alterations and protein expression in a cohort of primary bladder cancer subtypes treated by cystectomy. Tissue microarrays (TMA) were constructed from 820 patients who underwent cystectomy at the Mayo Clinic between 2000 and 2020. In 209 patients, TMAs were constructed from a concurrent pelvic lymph node metastasis. ERBB2 copy numbers were assessed by fluorescence in situ hybridization (FISH) and protein expression by immunohistochemistry (IHC). In a subset of 756 patients, ERBB2 ploidy was compared to previously assessed NECTIN4 ploidy. ERBB2 amplification was present in 59 (7.4%) of 820 bladder cancers and amplification varied by subtype with amplification most frequently identified in micropapillary carcinoma (19%), conventional urothelial carcinoma (8%), urothelial carcinoma with squamous differentiation (7%) and pure squamous cell carcinoma (5%), and less frequently in nested (3%), plasmacytoid (3%), high-grade neuroendocrine (2%) carcinoma, and sarcomatoid carcinoma (0%). There was a significant association between ERBB2 amplification and protein expression in primary and nodal metastases (p < 0.0001). ERBB2 amplification occurred in 26 (12.4%) of 209 nodal metastases and there was concordance in amplification between primary and nodal metastases (kappa = 0.61). Discordance occurred in 15 cases (7.2%) most commonly due to gain of amplification in the nodal metastasis. There was agreement in protein expression between primary and lymph node metastases (kapp = 0.52), and the nodal metastases had a significantly higher expression (p < 0.001). In a subset of five patients with amplified primary tumors and distant metastases, the metastatic tumor was amplified in all cases. Co-amplification of NECTIN4 and ERBB2 occurred in 18 (2.4%) cases. The frequency of ERBB2 amplifications varied by bladder cancer subtype, and amplification resulted in increased protein expression. Nodal metastases had a higher frequency of amplification and protein expression than the primary tumors. A small subset of tumors exhibited co-amplification of ERBB2 and NECTIN4.

Abstract Background: Spatial cellular ecosystems in the tumor microenvironment (TME) form dynamic signaling hubs that critically influence cancer disease progression and response to therapy, including response to immune checkpoint inhibitors (ICIs). However, tumor sampling bias and the impracticality of acquiring serial tumor biopsies have made it challenging to profile the TME clinically. To address this challenge, we developed Liquid EcoTyper, a multi-analyte AI framework to quantify TME spatial cellular ecosystems—termed spatial ecotypes (SEs)—noninvasively from cell-free DNA (cfDNA) methylation data. Methods: In previous work, we discovered nine spatial ecotypes, including SEs associated with ICI response (e.g., SE7 with benefit, SE4 with resistance), and quantified them from 1,249 bulk tumor RNA-seq profiles of melanoma, non-small cell lung cancer (NSCLC), and bladder cancer (BC) patients (Cancer Res (2025) 85 (8_Supplement_1): 153). Here we trained Liquid EcoTyper, an interpretable deep learning model, to transfer SE profiling to cell-free DNA using CpG methylation profiles. Performance was quantified using simulated and real data, including methylation profiles (EM-seq) of plasma cfDNA paired with tumor biopsy-derived SE levels determined by EM-seq (n=20 pairs) or 10x Visium (n=15 pairs). Clinical outcome prediction was evaluated using pretreatment plasma from patients treated with ICI alone (n=78 melanoma pts), chemotherapy and ICI (n=25 NSCLC pts), and enfortumab vedotin and ICI (n=10 localized muscle-invasive BC (MIBC) pts). Tumor mutational burden (TMB), tumor PD-L1, or circulating tumor DNA (ctDNA) were profiled as a comparator where possible. Results: We observed striking concordance between plasma-derived SE levels and tumor biopsy-confirmed SE levels from the same patients, demonstrating that liquid biopsy analysis of cfDNA methylomes can recapitulate TME spatial biology. Underscoring specificity, no reliable SE signal was detectable from peripheral blood mononuclear cells. In pre-ICI plasma, liquid SE levels were significantly associated with ICI-based response (SE7) versus resistance (SE4) in patients with melanoma, NSCLC, and MIBC, with a mean cross-cancer area under the curve (AUC) of 0.87 for SE7 (range 0.8-0.97) and 0.81 for SE4 (range 0.76-0.85)—far surpassing TMB, tumor PD-L1, and ctDNA in evaluable patients, both in binary analyses of response and multivariable models of survival. Our results also showed potential to predict pathologic complete response in the neoadjuvant setting. Conclusion: Liquid EcoTyper is a scalable noninvasive AI-based framework for spatiotemporal assessment of the TME. By enabling TME-informed risk stratification without surgical biopsies, Liquid EcoTyper has potential to enable more precise and actionable decision making in patients with solid tumors. Citation Format: Erin L. Brown, Wubing Zhang, Abul Usmani, Noah Earland, Ayesha Hashmi, Chibuzor Olelewe, Anushka Viswanathan, Pradeep S. Chauhan, Minji Kang, Chloé B. Steen, Hyun Soo Jeon, Susanna Avagyan, Irfan Alahi, Nicholas P. Semenkovich, Matteo Bergsagel, Janella C. Schwab, Chloe M. Sachs, Faridi Qaium, Peter K. Harris, Antonella Bacchiocchi, Qingyuan Cai, Andrew J. Gentles, Rondell P. Graham, Peter C. Lucas, Ryan C. Fields, Jacob J. Orme, Aaron S. Mansfield, Mario Sznol, Ruth Halaban, David Y. Chen, Aaron M. Newman, Aadel A. Chaudhuri. Liquid biopsy profiling of the tumor microenvironment to determine response to immunotherapy regimens across solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 94.

OBJECTIVES:Sarcomatoid urothelial carcinoma (sUC) is associated with poor clinical outcomes. Herein, we evaluated clinicopathologic features (including PD-L1 expression) for institutional cases. METHODS:Sixty-five patients with sUC treated by radical cystectomy were matched for age, sex, and pathologic stage to 190 patients with pure urothelial carcinoma (UC). Outcomes were evaluated using the Kaplan-Meier method. Immunohistochemistry (IHC) results for tumor-specific PD-L1 expression in sUC were quantified using H-scores (range, 0-300). Cases with constitutive PD-L1 expression (cPD-L1; H-score ≥240) were evaluated for amplification events using fluorescence in situ hybridization (n = 28), mate-pair sequencing (Mpseq; n = 6), RNA sequencing (n = 5), and targeted next-generation sequencing (n = 8). PD-L1 regulatory pathways were evaluated using gene set enrichment analysis in the Cancer Hallmark dataset. RESULTS:Most patients with sUC had advanced disease (≥pT2, 62/65, 95%), without significant differences in overall and cancer-specific survival, when matched to pure UC. Median PD-L1 H-scores using different clones were 100 (SP142), 120 (SP263), and 195 (22C3). cPD-L1 was seen in 43% (28/65) of cases of sUC that were enriched for TP53, TERT, and CDKN2A/B alterations. PD-L1 amplification was identified in 7 (of 28, 25%) of these cases. Bionformatics analysis consistently identified IL6-JAK-STAT3 and interferon α/γ signaling in sUC with cPD-L1 expression. CONCLUSIONS:Our results suggest that cPD-L1 expression in most sUC occurs secondary to IL6-JAK-STAT3 and interferon α/γ signaling. This provides a biologic rationale for evaluating response to immunotherapy in this patient population.

Objectives/Goals: The impact of genetic alterations on survival in patients with neuroendocrine prostate cancer (NEPC) is unclear. This study assessed how genetic alterations and tumor mutational burden (TMB) affect overall survival (OS) in patients with NEPC treated at Mayo Clinic. Methods/Study Population: Demographic, clinicopathologic, and genomic data from patients with NEPC treated at Mayo Clinic (2015–2025) were abstracted from electronic medical records. Patients had consented to research and received at least one cycle of therapy. Descriptive statistics summarized patient characteristics, and survival was estimated with Kaplan–Meier analysis. OS was compared by disease type (de novo vs treatment-emergent NEPC), TMB (high vs low), and RB1, TP53, and PTEN alteration status. Results/Anticipated Results: Among 66 patients in the study, the average age at NEPC diagnosis was 67.5 years. There were no significant differences between the age at diagnosis of de novo and treatment emergent NEPC (t-NEPC). t-NEPC made up 77.3% of the cohort. Median follow-up was 46.5 months (IQR 28–120). The most common alteration was TP53. RB1 alterations were associated with significantly shorter OS compared to patients without RB1 alterations (mOS Not Reached (NR) vs 13.8 months; p = 0.0056). Similarly, patients with high TMB had worse overall survival (mOS NR vs 14.9 months; p = 0.077). We did not observe worse OS in patients with alterations in TP53 or PTEN. RB1 alteration and high TMB were the strongest predictors of worse survival. Discussion/Significance of Impact: RB1 alterations and high TMB predict poor survival in patients with NEPC, highlighting potential biomarkers for risk stratification. TP53 and PTEN did not significantly affect OS. Early genomic profiling and targeted management of actionable alterations such as BRCA and ATM may improve survival and inform future translational studies.

Purpose/objectives:Metastasis directed therapy (MDT) with stereotactic body radiotherapy (SBRT) has demonstrated clinical benefit among select oligometastatic prostate cancer (PCa) patients. The outcomes of SBRT to the left supraclavicular lymph nodes (SCLNs) are examined. Materials/methods:Between 2017 and 2024, 16 (3.8%) of 419 patients with PCa metastatic to lymph nodes were found by prostate-specific PET to have SCLN involvement. Survival, relapse patterns, and toxicity are analyzed. Results:At initial PCa diagnosis, median PSA was 6.7 ng/mL (range 2.1-315) with 50% of patients having Gleason score of 8-10. Mean time from initial diagnosis to SCLN metastasis was 10.4 years with median PSA of 2.0 ng/mL and median number of involved SCLNs of 1.5 (range 1-10). The most common fractionation scheme was 35 Gy in 5 fractions daily (44%) with 81% of patients receiving concurrent hormonal therapy. No grade ≥ 2 toxicities were reported. Local relapse-free survival at 5 years was 90.9%. Mean distant progression-free survival was 16.7 months (95% CI: 7.9-25.5). Mean prostate cancer-specific survival (PCSS) and overall survival were 4.6 years (95% CI: 3.6-5.6) and 4.0 years (95% CI: 2.8-5.1), respectively. Patients with castration-sensitive disease had 100% 5-year PCSS, and 58.3% for those with mCRPC. Conclusion:SBRT to SCLNs was well tolerated with no significant toxicity. Durable local control was satisfactory. The presence of SCLN metastases is frequently a harbinger of additional metastatic progression which suggests that patients require close monitoring and could benefit from the addition or intensification of systemic therapy.

BACKGROUND:Clival metastases are a rare and clinically aggressive manifestation of advanced prostate cancer, associated with cranial nerve palsy and poor survival. The molecular features of prostate cancers giving rise to clivus metastases remain unknown. PATIENTS AND METHODS:We performed a multi-center retrospective study across six institutions, identifying prostate cancer patients with radiographically confirmed clival metastases and available next-generation sequencing (NGS) data. Baseline characteristics and clinical outcomes were collected. Genomic alterations from tissue- and/or blood-based assays were aggregated at the patient level and compared with a publicly available metastatic castration-resistant prostate cancer (mCRPC) cohort (SU2C/PCF). RESULTS:Fifty-nine patients with clival metastases contributed 87 molecular assays. More than half of patients had Gleason grade group 5 cancer and presented with de novo metastatic (M1) disease. The median interval from initial prostate cancer diagnosis to clival metastasis was 71.4 months (95% CI, 42.0-101.7), while median overall survival following clival involvement was only 15.3 months (95% CI, 6.9-22.8). Compared with the SU2C/PCF mCRPC cohort, clival metastases showed significant enrichment of BRAF and CHEK2 alterations as well as homologous recombination repair (HRR) with relative depletion of AR-related, PI3K pathway, and G2-M pathway alterations. CONCLUSION:Prostate cancers giving rise to clival metastases exhibit a distinct molecular profile enriched for DNA damage-repair and RAF kinase alterations, suggesting unique metastatic biology and potential therapeutic vulnerabilities.