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88 Background: The VISION (NCT03511664) and PSMAfore (NCT04689828) clinical trials have demonstrated the effectiveness of 177 Lu-PSMA-617 in patients with mCRPC who have previously received androgen receptor pathway inhibitors (ARPIs) with or without taxane-based chemotherapy. Sipuleucel-T is used for treatment of mCRPC in routine clinical practice, particularly among community urologists; however, to date, there are no data available to understand the effectiveness of 177 Lu-PSMA-617 in patients previously treated with sipuleucel-T. Methods: This was a retrospective, observational study of adult patients with a diagnosis of mCRPC who received 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, and had a history of treatment with sipuleucel-T. Data were obtained from the PRECISION data platform, a harmonized dataset of patients with advanced prostate cancer in the US that integrates electronic health records and claims data from community, academic, urology, and medical oncology settings. The index date was the date of 177 Lu-PSMA-617 initiation. Patient characteristics and prostate-specific antigen (PSA) response rates were evaluated descriptively. Progression-free survival (PFS), defined as the time from 177 Lu-PSMA-617 initiation to disease progression or death, was analyzed using Kaplan–Meier curves. Results: A total of 290 patients met the inclusion criteria, of whom 72% were White and 12% were Black. At index, 32% of patients were treated in urology and 68% in oncology settings. The median age was 74 years, the median baseline PSA was 35.3 ng/mL (interquartile range [IQR] 10.0–99.2 ng/mL), and 57% of patients had a Gleason score of ≥8. In addition to sipuleucel-T, prior to 177 Lu-PSMA-617, 97% of patients had received ≥1 ARPI and 79% had received ≥1 taxane. The median follow-up for this cohort was 9.4 months (IQR 5.3–17.5 months). Among 144 patients with available PSA values both before and during 177 Lu-PSMA-617 treatment (representing 50% of the cohort), PSA response rates were as follows: a ≥50% reduction in PSA from baseline (PSA50) was observed in 60%, PSA80 in 42%, and PSA90 in 33% of patients. Overall, the median PFS was 15.2 months (95% confidence interval [CI] 11.6–19.4 months). Conclusions: In this real-world analysis of patients who received 177 Lu-PSMA-617 after sipuleucel-T treatment, the median PFS was similar to that observed in clinical trials, suggesting that 177 Lu-PSMA-617 can be sequenced after sipuleucel-T treatment in appropriate patients.

81 Background: In the PSMAfore clinical trial, 177 Lu-PSMA-617 achieved a PSA50 (defined as a ≥50% reduction in prostate-specific antigen [PSA] from baseline) response rate in 58%, a median radiographic progression-free survival (PFS) of 12 months, and a median overall survival (OS) of 25 months among taxane-naïve patients with mCRPC who had received one prior androgen receptor pathway inhibitor (ARPI). The aim of the present study was to evaluate the real-world effectiveness of 177 Lu-PSMA-617 in taxane-naïve patients with mCRPC who had received one or more prior ARPIs. Methods: This retrospective, observational study included taxane-naïve adults with mCRPC initiating 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, after ≥1 prior ARPI. All data for the study were extracted from the PRECISION data platform, a harmonized dataset of patients with advanced prostate cancer in the US treated in a variety of clinical settings. The index date was the date of 177 Lu-PSMA-617 initiation. Patient characteristics and PSA response rates were evaluated descriptively. PFS, defined as the time from 177 Lu-PSMA-617 initiation to progression or death, was estimated using Kaplan–Meier methodology. Results: A total of 500 patients were included. The median age was 75 years, 75% of patients were White and 8% Black, and 18% were treated in urology centers while 82% were treated in oncology centers. The most common site of metastasis was bone (77%), followed by lymph node (21%), visceral (12%), and unknown (5%). Overall, 51% had received 1 previous ARPI while 49% had received ≥2. The median baseline PSA was 26.7 ng/mL (interquartile range [IQR] 10−105 ng/mL) and the median time from mCRPC diagnosis to 177 Lu-PSMA-617 initiation was 23.6 months. The median number of 177 Lu-PSMA-617 cycles received was 4 (IQR 2−6). Among 219 patients with available PSA measurements both before and during 177 Lu-PSMA-617 treatment (representing 44% of the cohort), PSA response rates were as follows: PSA50 in 137 (63%), PSA80 in 86 (39%), and PSA90 in 56 (26%) patients. Overall, the median PFS was 13.5 months (95% confidence interval 11.7–14.7 months). Conclusions: The effectiveness of 177 Lu-PSMA-617 as a standard-of-care treatment in real-world, taxane-naïve patients with mCRPC who had received prior treatment with ≥1 ARPI is consistent with results from the PSMAfore trial, confirming the applicability of those findings to the real-world population now eligible for 177 Lu-PSMA-617. Further research on sequencing 177 Lu-PSMA-617 after one or more prior ARPIs in taxane-naïve patients with mCRPC is needed to guide optimal treatment sequencing in clinical practice.

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.

79 Background: In March 2025, the indication for 177 Lu-PSMA-617 was expanded to include prostate-specific membrane antigen (PSMA)-positive patients with mCRPC treated with ≥1 androgen receptor pathway inhibitor (ARPI) and considered appropriate to delay taxane-based chemotherapy. With 177 Lu-PSMA-617 moving earlier in the treatment journey, it is important to understand the clinical activity of other systemic therapies after 177 Lu-PSMA-617. The aim of this study was to evaluate the clinical outcomes among patients with mCRPC receiving a systemic therapy after 177 Lu-PSMA-617 treatment. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a proprietary dataset developed by Novartis representative of patients with advanced prostate cancer in the US from diverse clinical settings. Patients with mCRPC treated with 177 Lu-PSMA-617 who received a systemic therapy ≥14 days after treatment with 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, were included. Systemic therapies included ARPIs (abiraterone, enzalutamide, darolutamide, apalutamide); chemotherapy (cabazitaxel, docetaxel, carboplatin, cisplatin, etoposide, mitoxantrone); immunotherapy (pembrolizumab, sipuleucel-T); poly (ADP-ribose) polymerase (PARP) inhibitors (niraparib, olaparib, talazoparib, rucaparib); and radium-223. Patient characteristics and prostate-specific antigen (PSA) response were evaluated descriptively. Progression-free survival (PFS) from subsequent therapy initiation was estimated using Kaplan–Meier methodology. Results: A total of 442 patients receiving any subsequent systemic therapy after 177 Lu-PSMA-617 were included. Overall, 95% of patients received ≥1 ARPI and 76% ≥1 taxane pre- 177 Lu-PSMA-617. The median age was 73 years. Most patients received a taxane (n = 188), an ARPI (n = 176), or a PARP inhibitor (n = 33) as their subsequent therapy. The median time to subsequent therapy initiation was 70 days (interquartile range 38−137 days) from the last 177 Lu-PSMA-617 administration. Among 299 patients receiving a systemic therapy after 177 Lu-PSMA-617 with PSA values available both pre-index and during subsequent treatment, 48% achieved a ≥50% reduction in PSA from baseline (PSA50), 31% a PSA80, and 18% a PSA90. The median PFS from the initiation of subsequent therapy was 8.6 months in the entire cohort; this was 10.7 months with a subsequent ARPI, 7.2 months with a subsequent taxane, and 7.1 months with a subsequent PARP inhibitor. Conclusions: In this real-world analysis, meaningful clinical responses were observed in a subset of patients who received subsequent systemic therapies after 177 Lu-PSMA-617.

78 Background: 177 Lu-PSMA-617 is currently under investigation in combination with an ARPI in those with metastatic hormone-sensitive prostate cancer (PSMAddition trial: NCT04720157). This observational study was performed to assess the effectiveness of 177 Lu-PSMA-617 in combination with an ARPI in patients with mCRPC in the real-world setting. Methods: This was a retrospective cohort study of adults with mCRPC in the PRECISION data platform, a comprehensive database of prostate cancer patients compiled from diverse clinical settings in the US. Patients who received 177 Lu-PSMA-617 during March 23, 2022–June 27, 2025 were identified, among whom two cohorts were selected for inclusion: those who had evidence of ARPI use (apalutamide, darolutamide, abiraterone, or enzalutamide) at any time during 177 Lu-PSMA-617 treatment (concomitant ARPI cohort), and those who had no other treatment for mCRPC during 177 Lu-PSMA-617 treatment (no concomitant therapy cohort). The index date was initiation of 177 Lu-PSMA-617. Patient characteristics and prostate-specific antigen (PSA) responses were evaluated descriptively. Progression-free survival (PFS), defined as the time from 177 Lu-PSMA-617 initiation to disease progression or death, was estimated using Kaplan–Meier analysis. Results: A total of 1,880 patients treated with 177 Lu-PSMA-617 were identified, 140 in the concomitant ARPI cohort and 1,740 in the no concomitant therapy cohort. The median age was 74 years. Demographic characteristics were balanced between the groups, except that median baseline PSA was lower in the concomitant ARPI cohort when compared with patients in the no concomitant therapy cohort (18 ng/mL vs. 32 ng/mL). Before 177 Lu-PSMA-617 initiation, 94.3% and 73.6% of patients in the concomitant ARPI and 80.9% and 56.7% in the no concomitant therapy cohort had received ≥1 prior ARPI and ≥1 prior taxane, respectively. PSA response rates were broadly comparable between cohorts. The median (95% confidence interval) PFS was 14.7 (11.7–21.3) months among patients in the concomitant ARPI cohort vs 12.5 (11.5–13.6) months in the no concomitant therapy cohort. Ongoing follow-up aims to evaluate the impact of combining ARPI with 177 Lu-PSMA-617 on long-term clinical outcomes, including overall survival. Conclusions: The results of this study demonstrate that 177 Lu-PSMA-617 delivers clinical benefits inpatients with mCRPC with or without ARPI; however, addition of an ARPI may potentially improve these benefits. Prospective randomized controlled studies are needed to confirm this.

776 Background: There continues to be a significant unmet need for safe, effective, and bladder sparing treatment options for patients with non-muscle invasive bladder cancer (NMIBC). TARA-002 is a lyophilized biological preparation for intravesical instillation containing inactivated cells of Streptococcus pyogenes (Group A, type 3) Su strain. TARA-002 rapidly enters cancer cells, activating TLR2 and NOD2 to trigger innate immunity, inflammation, and potential immunogenic cell death. ADVANCED-2 (NCT05951179) is an ongoing Phase 2, open-label study to evaluate the safety and efficacy of intravesical TARA-002 in adults ≥ 18 years with high-grade (HG)-NMIBC CIS (± Ta/T1). Preliminary results showed promising complete response (CR) rates and durable responses in patients with HG NMIBC treated with TARA-002 (Jayram et al. AUA 2025). This abstract presents pooled safety data of TARA-002 from the BCG-naïve cohort and BCG-unresponsive cohort of the ADVANCED-2 study. Methods: The ADVANCED-2 study includes 2 cohorts of BCG-naïve (Cohort A) and BCG-unresponsive (Cohort B) participants. Key exclusion criteria include penicillin allergy; history of ≥ T2 bladder cancer, nodal, or metastatic disease; and concomitant prostatic or upper tract urothelial involvement. Each participant is treated with TARA-002 to receive induction (6 weekly doses), reinduction (if persistent disease at 3 months), and maintenance (through 24 months). Response is assessed every 3 months for 2 years. Long-term follow-up is conducted up to 60 months. Safety is monitored throughout the study. Results: As of 07-October-2025, 60 participants (median age: 74; range: 45 to 92), have been enrolled and exposed to TARA-002: 31 BCG-naïve (Cohort A) and 29 BCG-unresponsive (Cohort B). In both cohorts, 18/60 (30.0 %) participants reported drug-related treatment emergent adverse events (TEAEs). Related TEAEs were Grade 1 (18/60; 30.0%) and Grade 2 (3/60; 5.0%), with no reported Grade 3-5 related TEAEs. Commonly reported related TEAEs (≥ 5%) included bladder spasm (10.0%), dysuria (13.3%), fatigue (6.7%), and micturition urgency (6.7%). Most TEAEs were mild and transient. In both cohorts, 10/60 (16.7%) experienced serious AEs (SAEs); 4/60 (6.7%) were Grade 2 and 9/60 (15.0%) were Grade 3. No participants experienced drug-related SAEs or drug-related TEAEs leading to withdrawal or death. Conclusions: TARA-002 monotherapy was well tolerated, thus demonstrating a favorable tolerability profile to date for the treatment of BCG-naïve and BCG-unresponsive HG NMIBC with CIS (±Ta/T1). TARA-002 has a promising safety profile as a bladder-sparing treatment in HG NMIBC across BCG exposure status. Updated safety data will be provided based on evaluable time points at the time of the presentation. Clinical trial information: NCT05951179 .

77 Background: The incidence of metastatic hormone-sensitive prostate cancer (mHSPC) is increasing in the US, likely due to a decrease in screening practices. There has also been a rapid increase in recent years in the number of treatment options that can improve progression-free and overall survival (OS) for these patients. The objective of the current study was to evaluate the clinical outcomes among patients with mHSPC treated in contemporary US clinical practice (2020 to 2025). Methods: This retrospective, observational cohort study used data from PRECISION, a harmonized dataset on advanced prostate cancer in patients in the US treated in a range of clinical settings. Patients aged ≥18 years who were diagnosed with mHSPC during 01/01/2020–01/01/2024 and who initiated ≥1 therapy (index date = first-line [1L] treatment initiation) were included. The study period was from 01/01/2010 to 06/30/2025. Patient characteristics at mHSPC diagnosis and treatment utilization were evaluated descriptively. Castration resistance-free survival (CRFS; defined as the time to castration-resistant prostate cancer or death) and OS were evaluated from index using Kaplan–Meier analysis. Results: A total of 27,708 patients were included (median age, 72 years); 20,015 (72%) were treated in community urology, 4994 (18%) in community oncology, and 2669 (10%) in academic oncology centers at index. Almost half of patients (47%) initiated 1L treatment with androgen-deprivation therapy (ADT) monotherapy, 44% initiated a 1L doublet regimen (36% ADT + androgen receptor pathway inhibitor [ARPI], 5% 1L ADT + radiotherapy, 2% 1L ADT + docetaxel), and 5% a 1L triplet regimen (ADT + radiotherapy + ARPI or docetaxel); the remaining patients received other regimens. The 5-year CRFS rate was 41%; this was significantly higher in patients with a 1L doublet (45%) or triplet (58%) regimen compared with patients with 1L ADT monotherapy (31%; p<0.001). Similarly, the 5-year OS rate was 59% overall and was significantly higher in patients with a 1L doublet (61%) or triplet (59%) regimen compared with patients with 1L ADT monotherapy (55%; p<0.001) (Table). Conclusions: Though both CRFS and OS rates appear to be increasing among real-world patients with mHSPC, >40% of patients in this study died within 5 years of initiating 1L treatment. Patients who received guideline-recommended combined systemic treatment regimens experienced improved CRFS and OS, confirming the importance of implementing therapies in practice that prolong survival. CRFS and OS rates from start of 1L therapy, by therapy type. CRFS rate (%) OS rate (%) 1 y 2 y 3 y 4 y 5 y 1 y 2 y 3 y 4 y 5 y Overall 68 58 51 46 41 93 84 76 67 59 ADT monotherapy 59 49 41 36 31 92 83 74 65 55 Doublet therapy 72 62 55 49 45 94 85 76 68 61 Triplet therapy 85 77 70 68 58 94 89 82 74 59

75 Background: Although the number of life-prolonging treatment options for pts with mHSPC has increased, initial real-world evidence has demonstrated slow uptake. This study utilized a large, contemporary, real-world dataset to evaluate the characteristics and treatment utilization among US pts with mHSPC in recent years. Methods: This retrospective, observational study used data from PRECISION, a harmonized dataset on pts with advanced prostate cancer. Adult men who were diagnosed with mHSPC during 01/01/2020–01/01/2024 (index date) and who initiated ≥1 therapy were included; the study period was 01/01/2010–06/30/2025. Pt characteristics were described at index. Treatment utilization was evaluated from index until progression to metastatic castration-resistant prostate cancer, death, or last follow-up. If an androgen receptor pathway inhibitor (ARPI), docetaxel, or radiotherapy was started within 4 months of index/androgen-deprivation therapy (ADT) start, it was considered a first-line (1L) combination; if it was started after >4 months, it was considered treatment intensification. All analyses were descriptive. Results: Among the 27,708 pts who met the inclusion criteria in PRECISION, 72%, 18%, and 10% were treated in community urology, community oncology, and academic oncology centers at index, respectively. Median age was 72 years; 62% were White; 43% were from the US South; 53% had synchronous and 54% had metachronous metastases (2% unknown). Median prostate-specific antigen level was 9 ng/mL (mean, 130 ng/mL). Prior to mHSPC diagnosis, 19% of pts had a prostatectomy and 17% had radiotherapy. Almost half of pts (47%) initiated 1L treatment with ADT monotherapy; 36% initiated 1L ADT + ARPI, 5% 1L ADT + radiotherapy, 2% 1L ADT + docetaxel, 5% 1L ADT + radiotherapy + ARPI or docetaxel, and 5% other regimens. From 2020 to 2023, 1L ADT monotherapy use decreased, while 1L combination use increased (Table). In addition, 19% of pts with 1L ADT monotherapy had evidence of subsequent treatment intensification, mainly the addition of an ARPI. Conclusions: In this study, use of 1L ADT monotherapy declined over time, accompanied by an increase in 1L combinations and treatment intensification. Nonetheless, approximately 1/3 of pts still did not receive a combination or intensification. Further research is needed to understand treatment trends in pts with mHSPC. Treatment patterns by index year. Pts, % 2020(n=5278) 2021(n=6203) 2022(n=7701) 2023(n=8526) 1L ADT monotherapy* 54 52 45 40 Subsequent treatment intensification* 18 19 20 18 1L ADT + ARPI* 29 33 38 42 1L ADT + radiotherapy 5 5 5 6 1L ADT + docetaxel* 3 2 2 1 1L ADT + radiotherapy + ARPI or docetaxel* 3 3 5 7 *p<0.001 for trend across years.

712 Background: Bladder cancer is one of the most common malignancies of the urinary tract. Glucagon-like peptide-1 (GLP-1) receptor agonists are widely used for the treatment of type 2 diabetes and obesity. Their pleiotropic benefits including improved insulin sensitivity, potential anti-proliferative and anti- inflammatory benefits may significantly benefit these patients by potentially influencing tumor biology. Our study aims to evaluate the impact of GLP-1 receptor agonists on outcomes among patients with bladder carcinoma with comorbid obesity, exploring potential interactions between metabolic modulation and disease behaviour. Methods: A retrospective cohort study was conducted using the US Collaborative Network TriNetX, covering January 2000 to December 2023, encompassing data from 105 global healthcare organizations. Adult patients aged 18 and above with bladder cancer and comorbid obesity were identified and then stratified into two groups based on treatment with GLP-1 agonists or not. The two groups were then propensity-matched based on age, sex, race, and common comorbidities. We followed these patients for 5 years to assess outcomes, including overall mortality, myocardial infarction, heart failure, chronic kidney disease (CKD), ischemic stroke, risk of metabolic dysfunction associated liver disease and need for hemodialysis. Results: We identified 1282 patients with bladder cancer and obesity who received GLP-1 receptor agonists, and 10238 patients with bladder cancer and obesity who did not receive GLP-1 therapy. The average age was 67.3 years in the first cohort and 69 years in the second cohort. After propensity matching, each cohort consisted of 1282 patients with similar baseline characteristics and ethnicity distribution. Our analysis found that over 5 years, patients with bladder cancer and obesity who received GLP-1 receptor agonists had a significantly lower risk of overall mortality (Hazard Ratio (HR): 0.611, 95% CI: 0.515 to 0.725, p-value =0.04), myocardial infarction (Risk difference: -4.418%, 95% CI: -6.608% to -2.228%, p-value <0.001), heart failure (Risk difference: -5.226%, 95% CI: -8.883% to -1.569%, p-value =0.005), CKD (Risk difference: -7.193%, 95% CI: -10.675% to -3.711%, p-value <0.001). There was no statistically significant difference in the risk of metabolic dysfunction associated liver disease and need for hemodialysis between the two subgroups. Conclusions: Our study revealed that patients with bladder cancer and obesity who received GLP-1 receptor agonists had a significantly lower risk of mortality, myocardial infarction, heart failure and CKD. Further longitudinal cohort studies are imperative to better understand these associations and guide evidence-based clinical practice in this population.

703 Background: The association of circulating tumor DNA (ctDNA) reduction with treatment response has been investigated across multiple malignancies. This study aims to assess the impact of ctDNA response on survival outcomes in patients receiving enfortumab-pembrolizumab (EV-P). Methods: We identified 32 patients with advanced urothelial carcinoma who received EV-P and had ≥2 ctDNA assessments with ≥1 detectable level. Deep molecular response was defined as >2-log reduction from highest ctDNA detection. Radiographic progression was determined from radiology reports documenting progression by RECIST criteria. Kaplan Meier analyses were performed to compute Hazard Ratios (HR) with 95% confidence intervals (CI) for radiographic progression free survival (rPFS), defined as time from treatment start to radiographic progression or death and overall survival (OS) defined as time from treatment start to death were computed. Log-rank tests were performed to compare PFS and OS in patients with deep molecular response to those without response. A p-value <0.05 indicated a statistically significant association with response. Results: Thirty-two patients were included (median age 71 years; range 39–90). Median follow-up was 10.6 months. At cutoff (10/1/2025), 26 patients were alive and 6 had died. Seventeen (53%) achieved a ≥2-log ctDNA reduction (responders), while 15 (47%) did not (non-responders). Progression-free survival was significantly longer in responders (log-rank P < 0.001); median PFS was 5.9 months (95% CI 2.4–NR) in non-responders and not reached in responders (HR 0.09, 95% CI 0.02–0.44; P = 0.0026). Median overall survival was 12.7 months (95% CI 10.0–NR) in non-responders versus not reached in responders (log-rank P = 0.011; HR 0.11, 95% CI 0.01–0.88; P = 0.037). At cutoff, 94% of responders and 67% of non-responders were alive. Conclusions: Achieving a >2-log decrease in ctDNA during EV + Pembrolizumab therapy was significantly associated with improved progression free and overall survival. These findings support ctDNA kinetics as a potential early biomarker of response warranting prospective validation. Clinical outcomes by >2-log ctDNA reduction status. Endpoint > 2-log drop (n = 17 ≤ 2-log drop (n = 15) Log-rank p Median (mo) ≤ 2-log > 2-log HR (95% CI) P C-index PFS 2 events (12%) 10 events (67%) 0.0002 5.9 (2.4–NA) NR 0.09 (0.02–0.44) 0.0026 0.77 OS 1 event (6%) 6 events (40%) 0.011 12.7 (10.0–NA) NR 0.11 (0.01–0.88) 0.037 0.73