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e21521 Background: Outcomes following tumor-infiltrating lymphocyte (TIL) therapy vary in real-world practice, and accessible predictors are needed to inform patient selection and timing of referral. We evaluated whether baseline disease burden, metastatic distribution, and treatment delivery factors are associated with outcomes following TIL therapy. Methods: We retrospectively analyzed patients with metastatic melanoma treated with TIL therapy across Mayo Clinic sites (N = 27 infused). Baseline disease burden was characterized using AJCC metastatic stage and organ-specific involvement. A composite high visceral burden variable was defined as the presence of M1d disease and/or liver metastases. Bridging therapy use prior to infusion was recorded. Post-infusion IL-2 exposure was categorized as low (0-2 doses) vs. high (3-6 doses). Best overall response (BOR) was summarized using RECIST-based standard criteria. Overall survival (OS) and progression-free survival (PFS) were measured from TIL infusion and estimated using Kaplan–Meier methods with univariable Cox regression. Results: Median age at infusion was 62.0 years; 59.3% were male. Melanoma subtypes included cutaneous (81.5%) and mucosal (18.5%). Bridging therapy was used in 48.1%. Baseline metastatic stage was M1a/M1b in 18.5%, M1c in 63.0%, and M1d in 18.5%. Median follow up was 8.3 months. BOR included complete response (18.5%), partial response (37.0%), stable disease (22.2%), and progressive disease (22.2%), yielding an objective response rate of 55.6% and disease control rate of 77.8%. Patients with high visceral disease burden experienced inferior OS vs. those without high visceral burden (median 5.2 vs 13.4 months; HR 4.77, 95% CI 1.22–18.63; p = 0.014). Bridging therapy was not associated with OS or PFS. Higher post-infusion IL-2 exposure (seen in 77.8% of patients) was associated with improved OS (median 9.0 vs 3.7 months; HR 0.16, 95% CI 0.04–0.67, p = 0.005), likely reflecting early post-infusion clinical tolerance rather than a causal treatment effect. Median PFS for the cohort was 3.6 months and did not differ by IL-2 exposure ( p = 0.3), metastatic stage ( p = 0.8), bridging therapy ( p = 0.7), liver metastases ( p = 0.2), or LDH above upper limit of normal ( p = 0.1). Conclusions: The above findings are hypothesis generating and will support evaluation in larger cohort. In this real-world cohort of patients treated with TIL therapy, baseline visceral disease burden was strongly associated with survival outcomes, while bridging therapy did not compromise post-infusion efficacy among patients proceeding to infusion. Post-infusion IL-2 exposure correlated with OS and likely reflects early treatment tolerance. These readily available clinical features may inform patient counseling, referral timing, and sequencing decisions as TIL therapy enters broader clinical use.

9573 Background: Clinical Stage III (cSIII) melanoma patients are at high risk of recurrence following therapeutic lymph node dissection (TLND) and adjuvant therapy. Neoadjuvant immunotherapy based regimens have shown promising results in this setting, with pathological response being the best predictor of recurrence free survival (RFS) and distant metastases free survival (DMFS). T-cell Receptor (TCR) abundance and clonality are being explored as biomarkers. Methods: In the phase II NeoACTIVATE (NCT03554083) trial, patients were treated based on BRAF status with 12 weeks of neoadjuvant atezolizumab, vemurafenib and cobimetinib (Arm A, BRAF-mutated) or atezolizumab and cobimetinib (Arm B, BRAF wildtype), followed by TLND and 6 months adjuvant atezolizumab. TCR sequencing (n=23) was performed on the pretreatment involved lymph node (iLN) and on the same node, along with an adjacent uninvolved node (uiLN) after TLND. The fraction productive of T cells (fpTC) was defined as the percentage of in-frame TCR sequences (capable of encoding a functional expressed receptor protein) of all TCR sequences identified. Simpson Clonality Index (SCI) was used to measure relative abundance of specific clones, with a higher score indicating a more monoclonal repertoire. Comparisons were made using the Wilcoxon Rank Sum test. Results: 30 patients were enrolled, 15 in each arm. 2 patients were not operated on, and one did not receive adjuvant treatment, leaving 27 patients for outcome analysis. 3-year RFS was 55.6% (95% CI 9.5%-77.8%), median of 62.2 months (95% CI 19-NR); DMFS was 64.3% (95% CI 48%-86.3%), median 62.2 months (95% CI 33.9-NR). The fpTC was higher in the pretreatment iLN for those without an RFS event (p=0.04) with a trend in the uiLN as well (p=0.06). Patients without a DMFS event had a higher fpTC in the uiLN (p=0.03) but not in the iLN. The SCI was significantly higher only in the post treatment iLN for patients without an RFS event (p=0.03) and was not significantly different when compared based on DMFS status. When performing pairwise comparisons of nodes based on recurrence status, we found that patients who did not suffer an RFS event had a significantly higher SCI in the post treatment iLN compared to the uiLN (p=0.02). Conclusions: Neoadjuvant immunotherapy and targeted therapy for cSIII melanoma can lead to durable RFS. Higher pretreatment fpTC as well as higher post-treatment iLN TCR clonality were both associated with improved RFS. These data indicate that TCR repertoire characteristics within iLN and uiLN may reflect differential immune responses to neoadjuvant therapy and could inform future studies evaluating biomarkers to stratify risk of recurrence and allow personalization of therapy. Clinical trial information: NCT03554083 . fpTC Simpson Clonality Index RFS event DMFS event RFS event DMFS event Pretreatment iLN 0.04 0.12 0.43 0.11 Posttreatment iLN 0.09 0.09 0.03 0.12 uiLN 0.06 0.03 0.79 0.48 Δ iLN (post-pre) 0.79 0.37 0.07 0.41 Δ posttreatment iLN – uiLN 0.21 0.21 0.02 0.08

9567 Background: Resected stage IIB/C and microscopic stage IIIA/B/C/D melanoma presents a significant risk of recurrence risk of 37 to 62% at 5 years (yrs). While 1 year of adjuvant PD1 therapy reduces this risk by approximately half, the individual patient’s baseline risk without treatment and their specific benefit from adjuvant PD1 remain unknown. We aimed to generate two separate predictive models for recurrence – one for untreated and one for treated pts - to calculate the individualised benefit of adjuvant PD1. Methods: Pts with resected stage IIB/C or microscopic stage IIIA/B/C/D melanoma, either treated with adjuvant PD1 or untreated at 13 major melanoma centres, and with at least 2 years of follow-up from surgery were included. We analysed pts demographics, disease characteristics, blood parameters, pathological and imaging data at baseline, and clinical outcomes. Propensity scores were estimated using logistic regression with covariates associated with treatment in univariate screening (p<0.05). Separate penalised multivariable logistic regression models were built to predict recurrence for treated and untreated pts. A tool based on these models was created to calculate the individual patient benefit from adjuvant PD1. Results: A total of 3560 pts was included, divided into untreated (discovery n=2384 and validation n=597) and treated (discovery n=404 and validation n=175) cohorts. The model for untreated pts included age, gender, primary site, histological subtype, Breslow thickness, ulceration, mitosis, number and site of regional lymph nodes (LN), mutation status and LDH (AUC 0.70 in discovery, 0.69 in validation). The model for treated pts included age, gender, Breslow thickness, site of regional LN, and mutation status (AUC 0.69 in discovery, 0.61 in validation). ADAPT-M (ADjuvant Anti-PD-1 Tool for Melanoma) calculates the individualized benefit of adjuvant PD1. For example, patient A, a woman ≤45 years old with a primary head & neck melanoma (superficial spreading, thickness >1-2 mm, no ulceration, 1 mitosis/mm 2 ), 2 clinically occult LN metastases in the neck, NRAS mutant, and normal LDH, has a 12-month recurrence risk of 21.9% untreated vs 2.3% treated (benefit 19.6%), and a 24-month risk of 41.1% untreated vs 6.4% treated (benefit 34.7%). While, patient B, a man ≤45 years old with a primary melanoma in the lower limb (nodular, thickness >1-2 mm, no ulceration, 1 mitosis/mm 2 ), 2 clinically occult LN metastases in the groin, BRAF V600 mutant, and normal LDH, has a 12-month recurrence risk of 14.2% untreated vs 11.8% treated (benefit 2.5%), and a 24-month risk of 28.0% untreated vs 30.1% treated (no benefit). Conclusions: ADAPT-M, a clinical tool that estimate individualized recurrence risks with and without adjuvant anti-PD1 therapy, quantifies the absolute benefit of treatment for pts with high-risk resected melanoma, facilitating personalized adjuvant therapy decisions.

9568 Background: Stage IIB/C cutaneous melanoma is associated with high recurrence risk, however stratification of risk in relation to time after surgery has not been comprehensively evaluated. We evaluated recurrence-free survival (RFS) at key time points, stratified by clinicopathologic factors, to identify patients (pts) at higher recurrence risk and personalize postoperative surveillance strategies. Methods: In this multi-institutional, international retrospective cohort study from the Sentinel Lymph Node Working Group database, we included pts with pathologic T3b/T4a/T4b and N0 disease who underwent surgical resection and sentinel node biopsy from 1994-2025. The type of first recurrence (local, regional, distant) was characterized based on time category (0-12, 12-24, 24-60, and 60+ months after surgery). Restricted mean survival time (RMST) analysis was used to measure the average survival time up to a specified time point (6-, 12-, 24-, and 60-months after surgery), and associations of clinicopathologic variables (age, sex, Breslow thickness, ulceration and lymphovascular invasion [LVI]) with RFS. Results: We included 2514 stage IIB/C pts from 19 sites in 4 countries, with a median follow-up of 53 (stage IIB) and 49 (stage IIC) months. 675 (27%) pts experienced a recurrence (92 [14%] local, 238 [35%] regional and 345 [51%] distant), and 400 (59%) recurrences occurred within 24 months. The proportion of distant recurrences as the first recurrence increased significantly with time, comprising 39%, 50%, 62%, and 59% of recurrences in the 0-12, 12-24, 24-60, and 60+ month time categories respectively (χ 2 p<0.001). No significant differences were observed for the included clinicopathologic variables for 6-month RMST estimates. At 12 months, RMST estimates for thickness ≥4 mm (11.2 vs 11.6 months for thickness 2-3.99 mm, p<0.001) and presence of LVI (10.7 vs 11.4 months, p=0.009) were significantly different. 24-month RMST estimates differed for male sex (20.7 vs 21.5 months vs females, p=0.002), thickness ≥4 mm (20.5 vs 21.9 months, p<0.001), and presence of LVI (19.0 vs 21.1 months, p<0.001). Lastly, 60-month RMST estimates differed for male sex (42.0 vs 45.2 months, p=0.001), thickness ≥4 mm (41.5 vs 46.2 months, p<0.001), LVI (36.0 vs 43.7 months, p<0.001), and age >65 years (41.5 vs 46.4 for age <42, p=0.022). Conclusions: In this real-world, multi-center analysis of pathologic stage IIB/C melanoma pts, recurrence patterns varied based on time after surgery. Breslow thickness, LVI, male sex, and age were significantly associated with earlier recurrence at different time intervals on RMST analysis. Additionally, given that >50% of first recurrences 12+ months after surgery were distant, active surveillance for distant relapses may be warranted.

9524 Background: Unresectable melanoma in-transit metastases (ITM) can pose a significant clinical challenge. Our recently published data comparing first-line treatments for ITM, isolated limb infusion or perfusion (ILI/ILP), immune checkpoint inhibitors (ICI) and intralesional talimogene laherparepvec (TVEC), found superior outcomes with TVEC. However, TVEC was used more often in patients with lower disease burden and earlier stage (IIIB vs. IIIC/D). Therefore, we sought to better investigate these differences with a propensity score-matched (PSM) analysis. Methods: A multi-institutional, international IRB- approved retrospective analysis was conducted for unresectable melanoma ITM from 2016-2022. PSM analysis comparing first-line ILI/ILP, ICI, and TVEC for was performed. Patients were matched for stage, number of ITM, anatomical site, CLND status, gender and age. Kaplan-Meier curves (OS, PFS, DMFS) and Cumulative incidence function (MSS) were used to visualize time-to-event outcomes in the PSM cohort, though both methods do not account for the matched structure. Results: 274 patients were identified, 120 female/154 male; 96 treated with ILI/ILP, 111 with ICI, and 67 with TVEC. Median follow-up was 40 months (range, 1-80). PSM was performed and identified 36 TVEC–ICI pairs and 27 TVEC–ILI pairs. These were combined resulting in a final cohort of 108 observations (45 TVEC, 36 ICI and 27 ILI). The groups were well balanced. No statistical difference was found for metastasis-free survival (DMFS), progression-free survival (PFS), melanoma-specific survival (MSS), and overall survival (OS) between treatment modalities. TVEC was associated with significant improvement in local PFS (median was 2.2 years (y) for ILI/ILP, 1.5y for ICI and not reached for TVEC, p=0.048). While not statistically significant, a clinical benefit was seen in PFS being longer for TVEC (2.1y for TVEC vs. 1.2y for ILI/ILP and 1.1y for ICI; p=0.2) and OS (not reached vs 2.9y for ILI/ILP and 5.2y for ICI; p=0.2). On mixed effect Cox regression proportional hazard model using the matched data set, there were no significant differences in any of the survival and recurrence outcomes. Conclusions: When patients are propensity-matched, there were no significant differences in first-line treatment modalities for unresectable melanoma ITM. Treatment with TVEC did result in clinically meaningful improved overall and local PFS and OS. This supports that selection of ITM therapy should incorporate an individualized approach, incorporating disease distribution, stage, burden, treatment side effects and patient priorities.

11064 Background: Local and state paid sick leave (PSL) mandates have been associated with increased use of preventive services, including cancer screening, and reduced emergency care utilization. Little research has examined PSL policies and cancer after diagnosis. This study evaluates associations of PSL policies and timely treatment initiation among women with early-stage breast cancer. Methods: We identified patients aged 18-64 years newly diagnosed with stages 0-II breast cancer from the National Cancer Database in 2004-2023 and linked then to area-level policy implementation, measured as the month and year the state, county, or city required PSL. Primary outcomes were receipt of definitive surgery or neoadjuvant therapy within 30, 60, and 90 days of diagnosis. We compared changes in treatment initiation between patients residing in areas with and without PSL policies during and after the month and year of diagnosis. We used a staggered difference-in-differences design to account for differential timing of implementation, adjusting for patient demographics, clinical, and area-level characteristics. Random errors were clustered at the state level. Supplemental analyses stratified by county-level unemployment rates and individual insurance coverage. Results: The study included 1,891,411 patients, of whom 249,313 (13.2%) resided in an area with PSL policies at diagnosis. Patients in areas with PSL policies were more likely to have Medicaid, reside in higher-income and metropolitan areas. PSL policy implementation was significantly associated with a 3.4 percentage point (PPT) increase in the probability of treatment ≤30 days (95% CI: 1.1-5.7), 3.0 PPT increase ≤60 days (95% CI: 1.6-4.3), 1.3 PPT increase ≤90 days (95% CI: 0.5-2.1) (Table). Improvements in timely treatment were concentrated in low-unemployment areas; no significant improvements were observed in high-unemployment areas. The magnitude of associations between PSL policies and treatment initiation was stronger among patients without private insurance than with private insurance. Conclusions: Local and state PSL mandates were associated with earlier treatment initiation among working-age patients with early-stage breast cancer, especially in areas with low female unemployment rate. Findings suggest that PSL policies play an important role in timely cancer treatment for employed women who may not have PSL through their jobs. Association of paid sick leave policies and breast cancer treatment initiation. Time from diagnosis to surgery/neoadjuvant therapy (days) DID PPT Lower 95% CI Upper 95% CI P-value Overall ≤30 3.4 1.1 5.7 0.004 ≤60 3.0 1.6 4.3 0.000 ≤90 1.3 0.5 2.1 0.001 Low female unemployment ≤30 2.2 -0.7 5.0 0.136 ≤60 3.8 1.8 5.8 0.000 ≤90 1.2 0.3 2.2 0.012 High female unemployment ≤30 1.8 -0.6 4.2 0.145 ≤60 -1.2 -4.5 2.0 0.459 ≤90 -1.4 -3.7 0.9 0.232

Background Patients with substance use disorder (SUD) have high rates of hospitalization, readmission, and prolonged lengths of stay. Objectives To conduct a systematic review and meta-analysis of the impact of addiction consult services in the inpatient setting for patients with SUD. Methods Five databases were systematically searched from their earliest available records through January 2025. Two authors independently screened articles, extracted data, and assessed the quality of each study with the Newcastle-Ottawa Scale for observational studies and the Cochrane risk-of-bias tool for randomized clinical trials. Pooled odds ratios (ORs) with 95% CIs were calculated for dichotomous outcomes, and mean differences were calculated for continuous outcomes. Results The search retrieved 20 studies that met inclusion criteria. The intervention for all studies was an addiction medicine consult, but the definition of this consult varied. The meta-analysis did not detect statistically significant differences in hospital length of stay, hospital readmission, or emergency department visits at 1 year among patients who received the consult compared with those who did not; however, many of these outcomes were likely underpowered. However, addiction medicine consults significantly improved the odds of inpatient initiation of medication for SUD (OR, 7.30; 95% CI, 3.30-16.13; P <.001) and postdischarge SUD treatment linkage and adherence (OR, 3.31; 95% CI, 2.06-5.32; P <.001). Conclusion Inpatient addiction consult services are associated with increased inpatient initiation of medication for SUD treatment and postdischarge treatment linkage and adherence. No clear association was identified between the consult and readmissions, emergency department utilization, or length of stay.

Abstract Background For many evidence criteria within v3.0 of the ACMG/AMP guidelines, methodologies have been developed to empower their use outside the stipulated evidence strengths. However, no such methodology has been established for case-control data (PS4). With the release of large-scale unselected case-control datasets and expansion of nationally-collected laboratory datasets enriched for pathogenic variant carriers, there is potential to combine datasets across ascertainment contexts in a more quantitative manner using novel likelihood ratio tools. Methods Using our published PS4-LR-Calculator, we calculated a combined log likelihood ratio (PS4-LLR) across five datasets (three unselected, and two enriched), and estimated enrichment of pathogenic variants in clinically-ascertained laboratory data using truncating variant prevalence. Results Data were combined for 10,817 missense variants from 325,345 female breast cancer patients and 671,006 controls of Western European ancestry for five breast cancer susceptibility genes ( BRCA1, BRCA2, PALB2, ATM, CHEK2 ). A combined LLR was produced for 4,690 missense variants; 927 variants received evidence towards pathogenicity (LLR≥ 1), and 3,242 received evidence towards benignity (LLR≤ -1). Conclusion This flexible, variant-level methodology combines nationally-collected ‘enriched’ datasets with unselected case-control cohorts, expanding the available information for case-control analysis, boosting power, enabling exploration of atypical penetrance and empowering variant classification.