Tran, Nguyen H.

593 Background: TP53 and CDKN2A are the most frequently mutated tumor suppressors in BTC, each linked to poor outcomes. Their co-alteration remains unexplored due to the current single-gene classification. Methods: This is an international multicenter study involving 35 institutions across 3 continents (North America, Asia, South America). Genomic profiling was performed on tissue or blood samples using NGS. Patients (pts) were categorized as wild-type (wt) TP53/ wt CDKN2A (WT/WT) (42%), mutated (mut) TP53 /wt CDKN2A (45%), wt TP53 /mut CDKN2A (5%), mut TP53 /mut CDKN2A (8%). Associations between TP53 / CDKN2A status , clinical and genomic features were evaluated using Chi-squared/Kruskal-Wallis tests adjusted for multiple comparisons. Overall survival (OS) from start of first-line systemic therapy was analyzed by Kaplan–Meier and multivariate Cox regression (covariates: age, sex, stage, primary site, first-line treatment, TP53/CDKN2A status), p or q<0.05. Results: We included 1079 pts with BTC. Median age 66 years with intrahepatic BTC (46%), gallbladder cancer (25%), extrahepatic BTC (22%), undefined (6%), ampullary cancer (< 1%). Most had de novo metastatic disease (54%), followed by recurrent (38%) and locally advanced disease (8%). Treatment regimens included chemotherapy (87%), chemo-immunotherapy (12%) and immunotherapy alone (<1%). The most frequently actionable genes were HER2 (8%), IDH1 (7%), BRAF (6%), FGFR2 fusions (4%), MSI-High (H) (3%). HER2 alterations were prevalent in mut TP53 /wt CDKN2A vs WT/WT (11 vs 4%, q = 0.002). IDH1 alterations were more frequent in WT/WT vs TP53 mut/wt CDKN2A (10 vs 4%, q < 0.001). FGFR2 fusions were more common in wt TP53 /mut CDKN2A vs WT/WT (17 vs 6%, q < 0.001), mut TP53 /mut CDKN2A (17 vs 3%, q = 0.001) and mut TP53 /wt CDKN2A (17 vs 1%, q < 0.001). MSI-H was enriched in mut TP53 /mut CDKN2A vs wt TP53 /mut CDKN2A (11 vs 2%, q = 0.035), mut TP53 /wt CDKN2A (11 vs 3%, q = 0.002) and WT/WT (11 vs 2%, q < 0.001). TMB-H was more prevalent in mut TP53 /mut CDKN2A vs mut TP53 /wt CDKN2A (16 vs 8%, q < 0.001) and WT/WT (16 vs 3%, q < 0.024). There was no significant difference in ORR, DCR and PFS among the four groups. mut TP53 /mut CDKN2A had the shortest median OS, while WT/WT had the longest (Table). Only 14% of mut TP53 /mut CDKN2A received regimens including immunotherapy. Conclusions: mut TP53 /mut CDKN2A represents a high-risk subset enriched with MSI-H and TMB-H pts, underscoring the need to prioritize the development of immunotherapy strategies. TP53 / CDKN2A status is prognostic, stratifying patients into distinct survival groups and supporting NGS use in the first-line setting. mOS (months) (95% CI) HR (95% CI) P-value WT/WT 21.4 (19.0-24.4) reference wt TP53 /mut CDKN2A 17.3 (12.4-25.9) 1.16 (0.79-1.71) 0.442 mut TP53 /wt CDKN2A 17.4 (16.0-19.2) 1.21 (1.01-1.45) 0.040 mut TP53 /mut CDKN2A 13.8 (11.5-18.1) 1.54 (1.13-2.09) <0.001

567 Background: IDH2 mutation is rare (1%) in patients (pts) with cholangiocarcinoma and there are no data on prognosis in these pts and response to first line (1L) chemotherapy or off-label IDH2 inhibitor enasidenib. Methods: This IRB approved retrospective study included consecutive pts 18 years or older with IDH2 mutated biliary cancer identified between 2010-2024 at 4 large academic centers. Pt characteristics, systemic therapy(ies), next-generation sequencing (NGS) and survival data were obtained via review of electronic medical records. Survival probabilities were estimated using the product-limit method of Kaplan-Meier using SAS (v9.4, Cary, NC). Results: In 40 pts who met criteria, 9 (22.5%) underwent curative intent resection/ ablation, 34 (85%) had recurrent or de novo locally advanced or metastatic stage and of them 33 (82.5%) received any therapy for advanced cancer. Of these 33 pts, 25 (75.7%) were female, 29 (87.9%) non-Hispanic White and 32 (97%) had intrahepatic subtype with a median (range) age of 65 (28-82) years. NGS on tissue (51.5%), plasma (21.2%) or both tissue and plasma (27.3%) identified IDH2 R172* in 28 (84.8%), I98T in 1 (3%), F278fs in 1 (3%) pts and not reported/missing in 1 (3%) pt. Most common co-altered genes included TP53 (27.5%), ARID1A (17.5%), PBRM1 (12.5%), CDKN2A (10%), BAP1 (10%). FGFR2 fusion or N/KRAS mutation was present in 2 (5%) pts each. Of 33 pts with advanced stage, 1L therapy was gemcitabine/platinum +/- devimistat or durvalumab in 84.9%. Median (95% CI) progression-free survival (PFS) on 1L chemotherapy and overall survival were 6.6 (4.1-7.8) and 16.3 (12.1-28.9) months, respectively. Eight of 33 (24.2%) pts with advanced stage received off label enasidenib as Nth line therapy with median PFS (95% CI) 3.9 (1.1-5.1) months. Conclusions: Most pts with IDH2 mutation had advanced ds with median survival similar to those with IDH1 mutated advanced cholangiocarcinoma. Off label enasidenib had modest benefit in this rare subset of pts and should be investigated further.

561 Background: For patients with aHCC, second-line treatment options are not well established. The primary aim of this study was to evaluate the efficacy of Futi, an FGFR 1-4 inhibitor, in combination with Pem as a second line therapy in patients with FGF19-expressing aHCC. Methods: Patients aged ≥ 18 years, with histological/cytological diagnosis or radiological diagnosis of HCC, Child-Pugh (CP) class A-B7, Barcelona Clinic Liver Cancer (BCLC) A, B or C, ECOG performance status of 0-2, and FGF19+, by in-situ hybridization or immunohistochemistry, received Futi 20 mg once daily plus i.v. Pem 200mg every 3 weeks. The primary endpoint was progression-free survival at 6 months (PFS6). Secondary endpoints include overall survival (OS). The study was designed to enroll 22 evaluable patients to detect PFS6 from 25% (historical control) to 47%, assuming a 1-sided alpha of 0.1 with 80% power. All patients provided written consent. Eligible patients with consent who started treatment are considered evaluable. Results: The study was closed to enrollment early at the request of funding agency due to poor accrual. Between 8/2021 and 3/2024, 14 patients enrolled with 1 patient withdrawing consent before beginning protocol treatment. Among 13 evaluable patients, median age was 72 (range: 60-87) years, 7 (53.8%) were male, 12 CP A (92.3%), 7 BCLC C (53.8%), with 7 (53.8%) having received prior liver directed therapy. Median PFS was 15 weeks (95% confidence interval [CI]: 9.0-Not Estimable) and PFS6 was 23.1% (95% CI: 8.6%, 62.3%). Objective response rate was 0% (95% CI: 0%, 24.71%) and stable disease occurred in 7 (53.9%) of patients. Median OS was 55.7 weeks (95% CI: 47.3-NE). Nine (69.2%) patients experienced at least 1 grade 3+ adverse event (AE), and 2 (15.4%) patients experienced at least a grade 4+ AE. One patient had a grade 5 AE unrelated to study treatment (acute kidney injury). Most commonly reported AEs (occurring in more than 31% of patients) were hyperphosphatemia (76.9%), fatigue (69.3%), diarrhea (61.6%), AST (53.9%) and ALT (46.2%), dry eye (38.5%), nail changes (38.5%), rash-maculo-papular (38.5%), and mucositis oral (38.5%). Conclusions: This prospective study evaluated the use of a targeted treatment in combination with immunotherapy following first line immune-based therapy. This combination had modest activity as a second line therapy for patients with aHCC but did not meet the primary endpoint. The safety profile was acceptable and consistent with prior reports. An optimal second-line regimen remains a critical need. Clinical trial information: NCT04828486 .

554 Background: Atezo/Bev is the 1 st -line standard for advanced hepatocellular carcinoma (aHCC). Optimal 2 nd -line therapy post-Atezo/Bev remains undefined. This study evaluates continuation of atezolizumab with a MKI versus MKI alone in the 2 nd -line setting. Methods: This multicenter, randomized phase II trial enrolled patients with unresectable aHCC who progressed on Atezo/Bev. Patients were randomized 2:1 to atezolizumab plus MKI (cabozantinib or lenvatinib; Arm A) or MKI alone (Arm B). Stratification factors included MKI choice, viral etiology, and alpha-fetoprotein levels. Dual primary endpoints were overall survival (OS) and progression-free survival (PFS). Secondary endpoints included objective response rate (ORR), duration of response (DOR), and safety. With 84 death and 89 PFS events, from 122 patients, this trial had 80% power to detect a hazard ratio (HR) of 0.556 in OS and HR of 0.571 in PFS with a one-sided type I error (alpha) of 0.05 for each endpoint. Results: Twenty patients were accrued across 5 U.S. centers, between 01/2022 and 03/2025, before early closure due to slow accrual. Eighteen received treatment (Arm A: n=13; Arm B: n=5). Baseline characteristics: median age 68 yr, extrahepatic 56%, Hep B+ 0%, Hep C+ 33%, NASH 33% and CP A (5 to 6) 100%. MKIs used were cabozantinib (Arm A: 6/13; Arm B: 4/5) and lenvatinib (Arm A: 7/13; Arm B: 1/5). Median follow-up was 28.0 months (mo), with 14 deaths reported. Median (95% CI) OS were 13.9 (7.1-Not Estimable [NE]) and 6.2 (5.1-NE) mo (Arm A and B respectively); and that of PFS 4.3 (2.3-NE) and 4.1 (3.7-NE) mo. ORR was 7.7% (1/13) in Arm A (responder received lenvatinib) and 0% (0/5) in Arm B. Grade ≥3 adverse events (at least possibly related) occurred in 46.2% of Arm A and 60.0% of Arm B patients. G3+ events occurring in >10% of patients included hypertension, fatigue, anorexia, and ALT elevation in Arm A; and hypertension, hallucination, nausea, hypomagnesemia, hypokalemia, mucositis, AST increased and colitis in Arm B. Conclusions: In this limited cohort, continuation of atezolizumab with MKI showed relative activity and manageable safety in aHCC post-Atezo/Bev. The AE profile for atezo/MKI is consistent with the known profile of respective agents. These findings support further investigation of immunotherapy-based combinations in the 2nd-line setting. Clinical trial information: NCT05168163 .

PURPOSE Neoadjuvant immune checkpoint inhibitors (nICIs) have demonstrated high response rates in deficient mismatch repair/microsatellite instability–high (dMMR/MSI-H) gastroesophageal adenocarcinoma (GEA). The NEONIPIGA and INFINITY trials demonstrated high rates of pathologic complete response (pCR) in this patient population. Furthermore, the INFINITY trial explored the feasibility of managing these patients nonoperatively, demonstrating promising results. This study aimed to evaluate clinical outcomes of nICIs in resectable dMMR/MSI-H GEA, with a focus on the feasibility of nonoperative management (NOM). MATERIALS AND METHODS This retrospective cohort study included patients with resectable dMMR/MSI-H GEA and treated with nICIs ± surgery at the Mayo Clinic. Patients were identified from institutional records, and clinical data were retrospectively reviewed. Primary outcomes were clinical complete response (cCR) and pCR. Secondary outcomes included event-free survival (EFS), radiologic complete response (rCR), and immune-related adverse events (irAEs). RESULTS A total of 26 patients treated between April 1, 2017, and July 30, 2025, were identified. Nine patients (34.6%) underwent surgery, of whom six (66.7%) achieved pCR. Seventeen patients (65.4%) pursued NOM, with 10 (71.4%) of 14 evaluable patients achieving cCR and 14 (82.4%) of 17 evaluable achieving rCR. One patient who initially achieved cCR had a local recurrence on surveillance endoscopy and underwent salvage endoscopic resection. At a median follow-up of 19.3 months, 15 (88.2%) of 17 patients in the NOM cohort were alive and metastasis-free, with EFS rates of 87.3% at 12 and 24 months for all patients. irAEs occurred in nine patients (34.6%), with no grade ≥3 toxicities. CONCLUSION In this retrospective cohort study, nICIs led to high cCR and pCR rates in resectable dMMR/MSI-H GEA, supporting the use of immune checkpoint inhibitors in this setting and the feasibility of NOM in select patients.

Background: Immunotherapy-based regimens have expanded the treatment landscape for unresectable hepatocellular carcinoma (uHCC); however, real-world data are limited. Methods: This retrospective, observational study used data from electronic medical records from Mayo Clinic sites across the United States. Patients with uHCC who initiated a first-line (1L) systemic therapy between June 2020–October 2022 with ≥2 follow-up visits were included. Treatment patterns, overall survival (OS), and post-index gastrointestinal (GI) bleeding were assessed by GI bleeding risk defined by Child–Pugh Class B or C, pre-index GI bleeding, uncontrolled hypertension, or significant varices and band ligation. Results: Of 186 included patients, 68.8% had GI bleeding risk and 31.2% did not. Atezolizumab plus bevacizumab was the most common 1L systemic therapy in patients with or without GI bleeding risk (72.7% and 29.3%, respectively). Median OS (95% confidence interval) with atezolizumab plus bevacizumab was 12.8 (8.0–19.3) months and not reached in patients with and without GI bleeding risk, respectively. OS rates with atezolizumab plus bevacizumab in patients with or without GI bleeding risk, respectively, were 52.3% and 70.6% at 12 months, 41.6% and 57.8% at 18 months, and 34.6% and 51.3% at 24 months. Post-index GI bleeding with atezolizumab plus bevacizumab occurred in 19.4% and 5.9% of patients with and without GI bleeding risk, respectively. Conclusions: During this study period, atezolizumab + bevacizumab was the most common 1L therapy for patients with uHCC, regardless of GI bleeding risk. OS rates with atezolizumab + bevacizumab were lower in patients with versus without GI bleeding risk. Findings highlight the unmet need for guidance on characteristics-driven treatment decisions.

Our study examined healthy human MASH and MASH-associated hepatocellular carcinoma (MASH-HCC) livers using bulk and scRNA sequencing, spatial transcriptomics, and immunohistochemistry. We found that ACSLs displayed differential and spatially heterogeneous expression. ACSL4 was abundant in tumor tissues, whereas ACSL5 was elevated in noncancerous MASH tissues. ACSL4 was mainly found in immune cells like natural killer cells and natural killer T cells in murine MASH-HCC, suggesting its role in tumor immune microenvironment modulation.

Objective: To develop and validate a risk score for predicting post-transplant recurrence in perihilar cholangiocarcinoma (pCCA) patients. Background: pCCA is an aggressive malignancy with a poor prognosis. Although neoadjuvant chemoradiation (CRT) followed by liver transplantation (LT) offers a potential cure for patients with unresectable, early-stage de novo or primary sclerosing cholangitis (PSC)-associated pCCA, post-transplant recurrence negatively impacts survival. Currently, no risk stratification tools exist. Methods: This retrospective study included consecutive patients with unresectable de novo or PSC-associated pCCA who underwent neoadjuvant CRT followed by LT at Mayo Clinic (1993–2024). Predictors of post-transplant recurrence were identified using multivariable Cox regression with LASSO variable selection. The Perihilar Cholangiocarcinoma Risk Estimation of Tumor Recurrence after Transplant (PRETREAT) risk score was created by assigning points from model coefficients. Score performance was evaluated by discrimination (c-statistic), internally validated with 10-fold cross-validation, and externally validated in a separate cohort. Survival outcomes were compared across 3 PRETREAT risk groups and between 2 time periods. Results: This study included 399 patients (development: 301; validation: 98). The 5-year cumulative incidence of post-transplant recurrence was 29.7% in the development cohort and 27.6% in the validation cohort. Multivariable analysis identified 4 independent predictors: macroscopic residual tumor on explant [hazard ratio (HR): 12.4], vascular encasement (HR: 2.18), lymphovascular invasion (HR: 2.04), and radial tumor diameter (HR: 1.02/mm). The PRETREAT score (0–22), based on these factors, demonstrated excellent performance in both internal and external validation (C-index 0.83 and 0.85, respectively). Patients were stratified into low-risk (0–7), moderate-risk (8–15), and high-risk (16–22) groups. The 5-year recurrence-free survival rates significantly differed across low-risk, moderate-risk, and high-risk groups (89.0%, 38.3%, and 15.4%, respectively; P<0.001). Over the last decade, overall survival improved significantly only in moderate-risk patients (70.4% vs 46.9%, P=0.024), without significant improvement in recurrence-free survival. Conclusions: The PRETREAT score provides a valuable tool for guiding post-transplant management of pCCA, enabling risk-stratified surveillance, and laying the foundation for future clinical trials.

Objective: This study aimed to evaluate the characteristics, clinical outcomes, and resource use of patients with unresectable hepatocellular carcinoma (uHCC) treated with first-line (1L) atezolizumab plus bevacizumab (A+B) at five United States (US) institutions: the Mayo Clinic, Houston Methodist, Moffitt Cancer Center, Mays Cancer Center, and University of Arizona. Methods: Treating oncologists extracted data from medical charts of patients with uHCC who were treated with A+B after 1 January 2019. Real-world progression-free survival (rwPFS) and overall survival (OS) were assessed using the Kaplan–Meier method for the overall cohort and for a “trial-like” subgroup with characteristics similar to those in the IMbrave150 trial (Eastern Cooperative Oncology Group Performance Status [ECOG PS] 0–1, Child–Pugh [CP] class A, albumin–bilirubin grade 1–2). Results: Of the 300 patients in the overall cohort (median age of 68 years; 12% ECOG PS ≥ 2; 73% CP A; 26% CP B; median follow-up of 8.7 months), the median rwPFS was 6.8 (95% confidence interval [CI]: 5.8, 8.4) months, and the median OS was 14.4 (95% CI: 12.3, 18.2) months. In the trial-like subgroup (n = 194), the median rwPFS was 8.8 (95% CI: 7.6, 12.1) months and the median OS was 19.5 (95% CI: 14.6, 24.7) months. A significantly lower proportion of patients with CP A compared with CP B (39.7% vs. 73.4%) experienced hospitalization within one year of A+B initiation, whereas hospitalizations due to treatment-related adverse events were similar. Conclusions: This study provides insights into the real-world effectiveness of 1L A+B in a diverse US patient cohort, with results from trial-like patients supporting the reproducible efficacy of A+B in clinical practice.

e16265 Background: The pivotal TOPAZ-1 trial established durvalumab plus gemcitabine and cisplatin (GC) as a new first-line standard of care for advanced biliary tract cancer (ABTC). However, weekly administration of GC can lead to significant toxicity limiting its tolerability in clinical practice. Based on previous studies, we implemented biweekly regimen of GC on days 1 and 15 together with durvalumab on day 1 of each 28-day cycle to optimize the treatment delivery and improve tolerability. Here, we report the Mayo Clinic experience with biweekly GC with monthly durvalumab in patients with ABTC. Methods: At our three-site institution, we retrospectively identified patients with ABTC between January 2021 and August 2024, who received biweekly GC with monthly durvalumab. Patient demographics, tumor characteristics, treatment details - treatment related adverse events (trAEs) graded according to the NCTCAE V5.0 were collected. Outcomes included median progression-free survival (mPFS), median overall survival (mOS) and clinically assessed overall response rate (ORR) and disease control rate (DCR). Results: 57 patients were included in our analysis, median age was 68 years (range 35-90), and 57.9% were females. 91.2% of patients had ECOG performance status of 0-1. 71.9% had intrahepatic cholangiocarcinoma, 19.3% extrahepatic cholangiocarcinoma and 8.7% gallbladder carcinoma. 70.2% had metastatic disease, 21 % locally advanced unresectable disease and 8.7% recurrent metastatic disease. Patients were followed for a median of 9.1 months (2.3-28.5). 91.2% of the patients received biweekly GC plus monthly durvalumab while 8.8% switched from weekly to biweekly GC plus monthly durvalumab due to treatment toxicities. Median number of treatment cycles was 5. Maintenance regimens included durvalumab (19.3%), gemcitabine/durvalumab (8.8%) and GC/durvalumab (8.8%). Median duration of follow up was 9.1 months (range 2.3 – 28.5). ORR was 36.9% and DCR was 72% (complete response 5.3%, partial response 31.6% and stable disease 35.1%). mPFS was 7.2 months, while mOS was 16 months. Grade(G) 3 or 4 trAEs included abnormal liver function tests (15.7%), infections (11.5%), anemia (8.7%), thrombocytopenia (5.2%), peripheral neuropathy (1.7%), acute kidney injury (1.7%). Immune-related AEs were noted in 6 patients (10.5%) including colitis, gastritis, hepatitis, myocarditis and hypothyroidism. There was no patient with severe neutropenia or febrile neutropenia. Only 5 patients (8.8%) stopped treatment due to trAEs. Conclusions: Biweekly GC on days 1 and 15 plus durvalumab on day 1 of each 28-day cycle is associated with a more favorable toxicity profile while maintaining efficacy similar to that observed in the TOPAZ-1 trial indicating that a de-escalation strategy is feasible with improvement in patient centered outcomes.