Citations

TPS577 Background: Pembrolizumab (pembro) for one year following resection of localized high risk clear cell renal cell carcinoma (ccRCC) in a phase 3 trial resulted in improvement in relapse-free survival and overall survival (Choueiri, NEJM 2024). However, 20% of patients still experienced a relapse within 2 years with no biomarker yet identified to predict who will respond to or needs adjuvant therapy. Addition of a tyrosine kinase inhibitor (TKI) to immunotherapy (IO) is a standard of care in metastatic ccRCC, but to date no studies have addressed the addition of a TKI to IO in the adjuvant setting. Subsequently, phase 3 STRIKE! was developed to explore the benefit of 6 months of tivozanib (tivo) added to pembro vs pembro alone in the adjuvant setting for resected high risk ccRCC. Methods: Eligible patients have an ECOG performance status ≤2 and a histologically confirmed diagnosis of RCC with clear cell component with or without sarcomatoid features after complete resection of the primary tumor, with pathology revealing pT2 grade 4 disease or any grade ≥ T3 or TxN1. Patients are also eligible if they developed metastasis within a year after resection and then underwent resection, definitive radiation or ablation of solid, isolated, soft tissue metastases (excluding brain and bone lesions) with no evidence of active disease (M1NED). Patients will be randomized 1:1 to intravenous pembro for 48 weeks with or without the addition of tivo 1.34 mg by mouth daily D1-21 q28D for 6 months stratified by stage (T2T3 vs T4/N1 vs M1NED) . With no limit on dose holds or interruptions of tivo, dose reductions of tivo to 0.89 mg D1-21 q28D or tivo 0.89 mg every other day are allowed. No dose reductions of pembro are permitted. Following baseline imaging to confirm no disease, imaging is performed every 12 weeks for first year, every 16 weeks for second year, every 24 weeks for third year and then annually until 5 years after registration or progression. The primary endpoint will be disease-free survival (DFS) as assessed by investigator, with secondary endpoints being overall survival, safety and tolerability. The study will enroll 1040 patients to detect a minimum detectable hazard ratio of 0.67 (24-month DFS 84% in experimental arm) with 90% power. Quality of life analysis will compare global quality of life and fatigue between the two arms. Imaging and specimens will be banked for future research. The study opened to accrual in April 2025 and at this time 106 patients have enrolled. Clinical trial information: NCT06661720 .

LBA630 Background: Enfortumab vedotin (EV) + pembrolizumab (pembro) is the established first-line standard of care for locally advanced/metastatic urothelial carcinoma and represents a novel neoadjuvant and adjuvant treatment strategy for patients with muscle-invasive bladder cancer (MIBC) who are ineligible for cisplatin-based chemotherapy. The randomized phase 3 KEYNOTE-B15/EV-304 study (NCT04700124) evaluates neoadjuvant and adjuvant EV + pembro followed by radical cystectomy plus pelvic lymph node dissection (RC + PLND) vs neoadjuvant chemotherapy followed by RC + PLND in participants (pts) with MIBC who are eligible for cisplatin-based therapy. Methods: Pts with clinical stage T2-T4aN0M0 or T1-T4aN1M0 MIBC (confirmed by central pathology and central imaging assessment) who were eligible for cisplatin-based chemotherapy and RC + PLND were randomized 1:1 to receive either 4 cycles neoadjuvant EV 1.25 mg/kg IV on days 1 and 8 + pembro 200 mg IV on day 1 Q3W, followed by RC + PLND, and adjuvant 5 cycles EV + 13 cycles pembro (EV + pembro arm) vs 4 cycles neoadjuvant gemcitabine 1000 mg/m 2 on days 1 and 8 + cisplatin 70 mg/m 2 on day 1 Q3W, followed by RC + PLND (cis + gem arm). The primary endpoint was event-free survival (EFS) by blinded independent central review. Key secondary endpoints were pathological complete response (pCR) rate by blinded central pathological review and overall survival (OS). Safety was a secondary endpoint; AEs of special interest were based on distinct prespecified lists for each drug. Results: A total of 405 and 403 pts were randomized to EV + pembro and cis + gem, respectively. Median time from randomization to the data cutoff date of October 27, 2025 was 33.6 months (range, 22.5–53.6). Baseline characteristics were generally balanced between groups. EV + pembro significantly improved EFS (median NR vs 48.5 mo; 24-mo estimated EFS rate 79.4% vs 66.2%; HR 0.53, 95% CI 0.41–0.70; 1-sided P <.0001), OS (median NR vs NR; 24-mo estimated OS rate 86.9% vs 81.3%; HR 0.65, 95% CI 0.48–0.89; 1-sided P =.0029), and pCR rate (55.8% vs 32.5%; estimated difference 23.4%, 95% CI 16.7–29.8; 1-sided P <.0001) vs cis + gem. Grade ≥3 treatment-emergent AEs occurred in 75.7% of pts with EV + pembro and 67.2% with cis + gem. Most common grade ≥3 drug-related AE of special interest for EV was skin reactions (14.1%); most common grade ≥3 AE of special interest for pembro was severe skin reactions (13.9%). Conclusions: Neoadjuvant and adjuvant EV + pembro significantly improved EFS, OS, and pCR rate compared with neoadjuvant gem + cis in pts with MIBC who were eligible for cisplatin-based chemotherapy. The safety profile of EV + pembro was consistent with prior experience with the combination. These results support EV + pembro as an effective perioperative treatment option in this setting. Clinical trial information: NCT04700124 .

794 Background: HER2 protein, encoded by ERBB2 gene, is the target of emerging therapies for patients (pts) with advanced urothelial carcinoma (aUC). High HER2 IHC expression (IHC 3+) is present in ~15% of pts with aUC, while >50% of pts have HER2 IHC 1+/2+/3+ expression. EVP is the preferred 1 st line regimen for pts with aUC, but the impact of HER2 status on EVP outcomes is unclear. Methods: We identified pts from the UNITE study with tumor samples tested for HER2 by IHC and another cohort with next-generation sequencing (NGS) data available. Outcomes were compared by HER2 IHC status (HER2 IHC 0/1+ vs 2+/3+) and separately based on ERBB2 status (alteration vs wild-type). X 2 test was used to compare observed response rate (ORR) and logistic regression was used to compare disease control rate (DCR). Duration of response (DOR), progression-free survival (PFS) and overall survival (OS) from EVP start were evaluated using log-rank test and Cox proportional hazards models. Multivariate analysis (MVA) included age, sex, race, ECOG PS, neutrophil:lymphocyte ratio, albumin, hemoglobin, primary tumor site, tumor histology, prior lines of treatment, and metastatic sites as covariates. Results: Among 521 pts treated with EVP from 16 sites, 112 had HER2 IHC data and 313 had NGS. Median age was 71, 74% were men, 84% Caucasian, 82% had ECOG PS 0-1, 65% pure urothelial histology, and 73% received frontline EVP. HER2 IHC distribution (n=112) was 27%/21%/37%/15% for 0/1+/2+/3+, respectively. ERBB2 alterations were present in 14% (44/313). Baseline characteristics were similar in HER2 0/1+ and 2+/3+ pts, except more primary bladder tumors in 2+/3+ pts (83% vs 63%, p=0.01). For the overall cohort (n=521), with a median follow up of 7.3 mos from EVP start, ORR was 54%, DCR 81%, median DOR (mDOR) 8.5 mos, median PFS (mPFS) 8.5 mos, and median OS (mOS) 19.8 mos. Pt outcomes by HER2 IHC status are shown (Table). In univariate analysis (UVA), pts with HER2 IHC 0/1+ had longer mOS compared to HER2 IHC 2+/3+, but this was not significant in MVA (HR: 0.5; CI: 0.2–1.3, p=0.17). No significant differences were observed in other outcomes. Evaluating clinical outcomes by ERRB2 status, no significant differences were seen for ERBB2 -altered vs wild-type pts. Conclusions: In this retrospective study, no significant differences were seen in EVP treatment outcomes based on HER2 IHC status or ERBB2 status. These findings are hypothesis-generating and require validation in larger and prospective cohorts. HER2 0/1+ (n=54)* HER2 2+/3+ (n=58) OR (95%CI, p) HR UVA (95%CI, p) HR MVA (95%CI, p) ORR 49% (23/47) 55% (27/49) 1.3 (0.6-2.9, p=0.5) - - DCR 79% (37/47) 88% (43/49) 1.9 (0.7-6.2, p=0.2) - - mDOR 11.7 mos 10.4 mos - 1.3 (0.7-2.4, p=0.4) 1.2 (0.4-3.3, p=0.8) mPFS 5.9 mos 7.1 mos - 0.8 (0.5-1.4, p=0.5) 1.1 (0.5-2.5, p=0.9) mOS 42.4 mos 18.7 mos - 2.3 (1.1-4.5, p=0.02) 2.0 (0.8-5.4, p=0.2) *HER2 0/1+ used as reference.

160 Background: To our knowledge, no tools are available to guide care in oligometastatic prostate cancer (omPC). Here, we leveraged individual patient-level data pooled from 8 randomized trials in the X-Met collaboration to construct CEREBRO, a tool for predicting patient-specific responses to various treatment scenarios. Methods: Patients with omPC from the STOMP, ORIOLE, SABR COMET, EXTEND continuous ADT, EXTEND intermittent ADT, ARTO, RADIOSA, and RAVENS trials were included. 6 patients (1%) with missing data were excluded. Treatment scenarios were defined as active surveillance (AS), metastasis-directed therapy (MDT), systemic therapy (ST), or MDT+ST. To account for varying baseline hazards, Weibull models were fit for overall survival (OS); progression-free survival (PFS); and castration-resistance free survival (CRFS) for patients with hormone-sensitive disease. Endpoint definitions were harmonized per X-Met framework. Results: Of 600 patients included (treatment scenarios: AS=50; MDT=153; ST=172; MDT+ST=225), 405 (67%) had hormone-sensitive omPC. With median follow-up of 38 months, median PFS, CRFS, and OS of all patients were 18, 70, and 84 months. In order of relative contribution, inputs for predicting outcomes were: treatment scenario, stage, prostate-specific antigen annotated by ADT status, metachronous vs synchronous presentation, imaging type, number of metastases, hormone sensitivity, and age. The model for each endpoint showed robust fit, calibration, superiority against the null model (per the likelihood ratio test), and risk stratification (Table). Median PFS times for model-defined low-, intermediate-, and high-risk strata were 46 months, 18 months, and 7 months ( p <0.0001). In addition, the PFS and OS models also showed strong discrimination via c index and a large interval of risk probabilities with additive clinical utility per decision-curve analysis (Table). A public webpage will be made available to facilitate prospective trial stratification, patient counseling for patient-specific outcome predictions for each potential treatment scenario, and forecasts comparing outcomes between treatment scenarios. Conclusions: CEREBRO is a high-performance tool, trained on robust prospective data from 8 randomized trials with routinely collected clinical variables, for predicting risk and treatment outcomes in omPC. Given the uncertainties in optimal timing of MDT and combination with ST, this tool has been built to facilitate current decision making. External validation is planned. Model summary. Endpoint C index (95% CI) Calibration Likelihood ratio p Risk strata p Net clinical utility observed between thresholds PFS 0.72 (0.70-0.75) 1.04 <0.0001 <0.0001 0.2-1.0 CRFS 0.63 (0.60-0.70) 1.01 0.02 0.004 0.2-0.5 OS 0.81 (0.76-0.86) 1.01 <0.0001 <0.0001 0.05-1.0

TPS890 Background: Although first-line (1L) EV + pembrolizumab has improved outcomes for patients with la/mUC, most experience disease progression, highlighting an unmet need for novel therapies. TROP2 is a glycoprotein highly expressed in several epithelial tumors, including UC. Dato-DXd is a TROP2-directed antibody–drug conjugate comprising an anti-TROP2 monoclonal antibody, a tetrapeptide-based cleavable linker, and a topoisomerase I inhibitor payload (DXd), designed to induce selective tumor-cell death and reduce systemic exposure to the payload. Dato-DXd has demonstrated durable efficacy and a manageable safety profile in patients with la/mUC both as monotherapy (TROPION-PanTumor01 [NCT03401385]) and in combination with immunotherapy (TROPION-PanTumor03 [NCT05489211]). We describe a phase 2/3 trial comparing the efficacy and safety of Dato-DXd + platinum CT (carboplatin or cisplatin) vs gemcitabine + platinum CT in participants with la/mUC with disease progression on or after EV + pembrolizumab. Methods: TROPION-Urothelial03 (NCT07129993) is a global, multicenter, randomized, open-label, phase 2/3 trial. In part A (phase 2), ~60 participants will be randomized 1:1 to receive Dato-DXd 4 or 6 mg/kg + platinum CT. In part B (phase 3), ~570 participants will be randomized 1:1 to receive Dato-DXd at the recommended phase 3 dose (determined using part A data) + platinum CT vs gemcitabine + platinum CT. Randomization in part A is stratified by assignment of platinum CT (carboplatin vs cisplatin), and in part B, by assignment of platinum CT, presence vs absence of liver metastasis at screening, and time to progression on 1L EV + pembrolizumab ( < 6 vs ≥6 months). Study treatment continues until disease progression, unacceptable toxicity, withdrawal of consent, death, loss to follow-up, or other reasons per protocol. Radiographic tumor assessments occur every 6 weeks for 54 weeks, then every 12 weeks. The primary endpoint of part A is objective response rate (ORR) by investigator per Response Evaluation Criteria in Solid Tumours, version 1.1 (RECIST 1.1). The dual primary endpoints of part B are progression-free survival (PFS) by blinded independent central review (BICR) per RECIST 1.1 and overall survival (OS). Secondary endpoints include duration of response by investigator per RECIST 1.1 (part A), and PFS by investigator per RECIST 1.1 and ORR by BICR and investigator per RECIST 1.1 (part B). In part A, ORR will be summarized with 2-sided 95% exact confidence intervals using the Clopper–Pearson method by trial group. In part B, PFS and OS will be compared between trial groups using a log-rank test stratified by randomization stratification factors, with hazard ratios from the stratified Cox regression model. Clinical trial information: NCT07129993 .

TPS290 Background: Landmark randomized trials established the survival benefit of adding D to ADT in mCSPC. Building on this foundation, subsequent trials (PEACE-1 and ARASENS) demonstrated further survival improvements when androgen receptor pathway inhibitors (ARPI) were added to the ADT + D backbone. However, the independent contribution of D within the triplet regimen remains unclear given lack of prospective evaluation. Additionally, tumor suppressor gene (TSG) alterations involving TP53, PTEN, and RB1 are frequently observed in PC and are associated with aggressive biology and poor outcomes, providing an opportunity to enhance prognostic accuracy and optimize selection of candidates for treatment intensification. We hypothesize that adding D to ADT plus A will improve survival compared to ADT + A in mCSPC and stratification by TSG status may identify different treatment effects across molecular subgroups. Methods: ASPIRE is an open-label, two-arm, randomized phase 3 study to assess the benefit of D added to ADT plus A for patients with mCSPC. Eligible patients include those with confirmed adenocarcinoma of the prostate with evidence of distant metastatic disease on conventional imaging and are appropriate to receive D. Patients with metachronous low-volume disease or PSMA-PET only disease are excluded. Candidates must have next-generation sequencing (NGS) results from a CLIA-certified tissue test available for TSG status stratification at registration. Eligible patients will receive ADT plus A (240 mg PO daily) +/- D for up to 6 cycles until progression of disease by PCWG3/RECIST version 1.1 criteria. Prior therapy with ADT (with or without ARPI) initiated within 120 days before registration is permitted. The primary endpoint is overall survival (OS). Secondary endpoints include OS by TSG status; radiographic progression-free survival (rPFS); time to castration resistance; symptomatic skeletal event–free survival; time to worsening of disease-related symptoms (NCCN-FACT FPSI-17); safety and tolerability (CTCAE v5.0); PSA90 response at 6 weeks and 6 months; time to PSA progression; and objective response rate in patients with measurable disease. The study will enroll 1200 patients and is currently actively accruing patients. Clinical trial information: NCT06931340 .

TPS277 Background: Recent advances in genomic sequencing have deepened our understanding of the molecular complexity of metastatic castration-resistant prostate cancer (mCRPC), revealing multiple actionable alterations that now inform biomarker-driven treatment strategies. Accordingly, germline and somatic tumor profiling is recommended for all patients with mCRPC. Beyond DNA aberrations, gene expression profiling can uncover additional therapeutic targets and pathway activations. The phase 2 PREDICT trial is leveraging both DNA and RNA alterations to guide rationally designed, biomarker-based therapeutic approaches for patients with mCRPC. Methods: This multi-center, multi-arm, biomarker-driven phase 2 umbrella trial is evaluating rationally selected therapies for patients with metastatic castration-resistant prostate cancer (mCRPC). The primary endpoint is objective response rate in patients with measurable disease, with secondary endpoints including radiographic progression-free survival, PSA response, time to first symptomatic skeletal event, overall survival, safety, and correlative biomarker analyses. Eligible patients must have progressive mCRPC of any histology, prior treatment with an androgen receptor pathway inhibitor (ARPI), and either prior or declined taxane chemotherapy, with both measurable and non-measurable disease permitted. Enrollment requires standard-of-care next-generation DNA sequencing from tissue or circulating tumor DNA performed in a CLIA-certified laboratory, and RNA-based allocation will use the CLIA-certified Caris MI Tumor Seek assay (whole exome and whole transcriptome sequencing) on tissue obtained within 12 months of study entry, with a real-time molecular tumor board reviewing results to confirm arm assignment. Patients with RB1 loss (DNA), an RB functional loss signature (RNA), or an NEPC signature (RNA) will receive the EZH1/2 inhibitor valemetostat; those with ≥2 of 3 tumor suppressor gene alterations (TP53, RB1, PTEN), FANC alterations (DNA), or SLFN11 overexpression (RNA) will receive cabazitaxel plus carboplatin; and those without study-defined alterations will receive physician’s choice of cabazitaxel, ARPI, or 177Lu-PSMA-617. The design permits incorporation of additional biomarker-defined arms, and up to 158 patients per arm (64 with measurable and 94 with non-measurable disease) will be accrued under a Simon two-stage minimax design, providing a one-sided type I error of 0.05 if the true response rate is 0.20 and 90% power if the response rate is 0.37 (Clinical trial information: NCT06632977). Clinical trial information: NCT06632977 .

696 Background: EVP is the preferred 1st-line therapy for patients (pts) with aUC. Upfront EV dose reductions may be utilized to enhance tolerance and minimize treatment-related toxicities when intolerance is anticipated. Prior studies of EV monotherapy suggest that starting dose 1.25 mg/kg resulted in exposure that maximized chance of response. We hypothesize that upfront EV dose reductions would not compromise EVP efficacy. Methods: Pts with aUC treated with EVP in the multi-site UNITE database were analyzed. Upfront dose reduction was defined as starting dose < 1.25 mg/kg. Correlation between clinical features and EV dose reduction were assessed using Fisher’s Exact test. Endpoints include progression-free survival (PFS) and overall survival (OS) from EVP initiation, assessed by Kaplan-Meier analysis and Cox models. Multivariable Cox analysis (MVA) included age (< 75 vs ≥ 75), ECOG performance status (PS) (0-1 vs 2-3), hemoglobin level (< 10 vs ≥ 10), and liver metastases (present vs absent), chosen in accordance with Bellmunt criteria. Correlation with investigator-assessed observed response rate (ORR) was determined using logistic regressions. All tests were 2-sided with p < 0.05 considered significant. Results: A total of 456 pts across 17 sites were included (median age 72; 77% Caucasian; 75% male; 26% upper tract primary; 66% pure UC; 77% ECOG PS 0-1; 17% with liver metastasis; 89% 1 st line EVP). Upfront dose reduction occurred in 96 pts (21%); 76 pts (79%) started at 1.0 mg/kg and 20 pts (21%) at 0.75 mg/kg. Upfront dose reduction was significantly associated with age ≥ 75 (p = 0.002), ECOG PS 2/3 (p = 0.04), and hemoglobin < 10 (p = 0.01) but not with liver metastasis (p = 0.9). Lower starting EV dose correlated with shorter median PFS (5 vs 6 months) and OS (9 vs 10 months), and lower ORR (28% vs. 60%) when compared to full dose (Table). In MVA adjusting for prognostic factors for PFS and OS, these associations were no longer statistically significant. Conclusions: In this real-world analysis, upfront EV dose reductions were most frequently used in pts with factors associated with frailty and poor prognosis, e.g. older age and ECOG PS 2/3, and were associated with lower ORR. When adjusted for these factors, upfront EV dose reductions were not associated with shorter PFS/OS though a trend towards inferior outcomes persisted. These differences in outcomes may reflect baseline risk factors rather than dose intensity; however, prospective investigation is required to validate our hypothesis-generating results. Association of upfront EV dose reduction with outcomes. Outcome (Upfront dose reduction vs no upfront dose reduction) Univariable analysis Multivariable analysis PFS: HR (95% CI), p 1.50 (1.11 – 2.02), 0.008 1.33 (0.95-1.86), 0.09 OS: HR (95% CI), p 1.56 (1.11-2.20), 0.01 1.41 (0.96-2.06), 0.08 ORR: OR (95% CI), p 0.35 (0.21-0.60), 0.0001 0.38 (0.21-0.67), 0.0009

496 Background: Approximately 10% of patients with renal cell carcinoma (RCC) have an associated venous tumor thrombus (VTT), the presence of which impacts surgical management and increases perioperative risk. Historical systemic therapy regimens had limited success in downsizing VTT; however, the impact of immune checkpoint inhibitors (ICIs) on VTT shrinkage is unknown. Our primary objective is to assess VTT shrinkage comparing responses to ICI versus non-ICI regimens. Methods: This multicenter retrospective cohort study included patients with RCC and VTT from 2006-2024 who received upfront systemic therapy. Patients were evaluated at tertiary referral centers across Mayo Clinic Rochester, Florida, and Arizona. Systemic therapies were categorized as ICI versus non-ICI regimens. VTT length was quantified by distance relative to the superior border of the renal vein ostium. The primary outcome was change in VTT length on serial imaging as measured by absolute length reduction (cm), RECIST version 1.1 criteria, and Mayo VTT level reclassification. Linear mixed-effect models (LMMs) identified associations with VTT shrinkage and clinicopathologic features. Results: A total of 108 patients with median age 65 years (IQR 57-71) were included, of whom 49 (45%) received ICI regimens. ICI regimens were associated with greater VTT shrinkage (1cm vs 0.1 cm, p=0.025), increased RECIST responses (51% vs 32%, p=0.046), and a higher rate downstaging per Mayo VTT level (33% vs 12%, p=0.008) compared to non-ICI regimens. On multivariable LMM analysis, ICI regimens remained more likely to result in VTT shrinkage compared to non-ICI regimens (-0.12 cm/month, 95% CI –0.24-0.00, p=0.046). Absence of abdominal lymphadenopathy was also associated with VTT shrinkage (-0.18cm/month, 95% CI -0.06- -0.30, p=0.004). Initial Mayo VTT level, IMDC risk, and number of metastatic sites were not associated with VTT shrinkage. Conclusions: Treatment with ICI-regimens resulted in VTT shrinkage and Mayo VTT level reduction. This is a particularly important area of exploration as radical nephrectomy and tumor thrombectomy carry up to a 40% risk of peri-operative major complications. These data support using ICI regimens for patients with RCC with VTT who are not candidates for upfront surgery and prioritizing ICI regimens in neoadjuvant clinical trials.

BACKGROUND: Left ventricular (LV) dysfunction is a potential cardioembolic source of ischemic stroke, but its role in recurrent stroke risk and treatment response remains unclear. We explore whether LV injury associates with the risk of recurrent stroke and modifies the association between anticoagulation and stroke recurrence using real-world data. METHODS: We performed a multicenter, retrospective study of Cardiac Abnormalities in Stroke Prevention and Recurrence cohort across 27 US sites. Patients with LV ejection fraction ≥20% were included. LV injury, defined as LV ejection fraction 20% to 40% and wall motion abnormality, was the primary exposure and treatment effect modifier. The treatment of interest was anticoagulant versus antiplatelet therapy. The composite outcome included recurrent stroke, major bleeding, or death. Outcomes were evaluated using unadjusted and inverse probability weighting adjusted Cox proportional hazards models, with treatment effect modification tested by LV injury status. RESULTS: Among 2685 patients enrolled, 2328 with complete data were analyzed (median age, 65 years; 49.8% female; median follow-up, 1.6 years). LV injury was present in 310 patients (13.3%). Overall, 535 events occurred: 258 recurrent ischemic strokes, 28 hemorrhagic strokes, 67 major hemorrhages, and 256 deaths. LV injury was associated with a higher unadjusted risk of the primary outcome (hazard ratio [HR], 1.51 [95% CI, 1.21–1.87]), though nonsignificant after inverse probability weighting adjustment (adjusted HR, 1.29 [95% CI, 0.97–1.70]). In the LV injury subgroup, anticoagulation versus antiplatelet therapy was associated with a lower risk of the primary outcome (adjusted HR, 0.24 [95% CI, 0.10–0.59]), relative to the non-LV injury subgroup (adjusted HR, 1.28 [95% CI, 0.83–1.95]; p[LV-interaction], 0.001). Similar interactions were seen for EF 20% to 40% (versus >40%; adjusted HR, 0.19 [95% CI, 0.04–0.86]; p[LV-interaction], 0.001) and wall motion abnormality (versus no wall motion abnormality; adjusted HR, 0.33 [95% CI, 0.15–0.73]). CONCLUSIONS: After cryptogenic stroke, anticoagulation in those with LV injury was associated with lower rates of recurrent stroke, major bleeding, and death. These findings warrant confirmation in a dedicated randomized controlled trial. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT06398366.