Lumish, Melissa

733 Background: Glucagon-like peptide-1 receptor agonists (GLP-1 RA) have advanced the treatment of type 2 diabetes mellitus (T2DM) yet their association with cancer risk remains subject of ongoing research. While case reports and pharmacovigilance data have linked GLP-1RA’s to pancreatitis, large randomized trials and observational studies have not consistently shown an increased risk of pancreatic cancer. Chronic pancreatitis (CP) is a well-established risk factor for pancreatic cancer, yet the impact of GLP-1 RA therapy in this high-risk population is unknown. In this study, we aim to evaluate the association between GLP-1 RA use and pancreatic cancer incidence among patients with CP, and among those with CP and T2DM. Methods: We performed a retrospective cohort study using ICD-10 codes within TriNetX, a healthcare database of over 150 million patients in the United States. In the first analysis, adult patients with pre-existing CP were identified, and the 5-year incidence of pancreatic cancer between GLP-1 RA (semaglutide, dulaglutide, tirzepatide, exenatide, liraglutide, and lixisenatide) users and non-users was compared from 2015-2025. In the subsequent analysis, we restricted the cohort to adults with CP and T2DM and repeated the comparison. Patients with prior diagnosis of pancreatic cancer were excluded from both analyses. All cohorts were propensity score matched (PSM) on age, sex, race, tobacco use, alcohol use, hypertension, hyperlipidemia, obesity, and pancreatic cysts. Results: We identified 95,391 with CP, including 3,139 GLP-1 RA users and 92,252 non-users. After PSM, GLP-1 RA use was associated with a lower incidence of pancreatic cancer (0.6% vs. 1.5%, OR 0.39 [0.22, 0.67]). Similarly, amongst patients with CP and T2DM, GLP-1 RA use was associated with a lower incidence of pancreatic cancer (0.7% vs. 1.6%, OR 0.44 [0.25, 0.75]). Conclusions: GLP-1 RA use was associated with a significantly reduced incidence of pancreatic cancer in all patients with CP and in those with CP and T2DM. Given the elevated cancer risk in CP, these findings suggest a potential protective effect of GLP-1RA use in this high risk population. Prospective studies will be important to further analyze and confirm this potential benefit.

605 Background: Multiple treatment modalities are available for localized hepatocellular carcinoma (HCC), and current Barcelona Clinic Liver Cancer (BCLC) guidelines recommend ablation for patients with a limited number of small tumors, not amenable to resection or transplantation. However, in recent years, stereotactic body radiation therapy (SBRT) has been increasingly used for localized disease. Patient outcomes based on treatment modality are not well understood. Methods: We conducted a retrospective analysis using the National Cancer Database (NCDB) to identify patients with a history of stage I/II HCC with tumors ≤ 5 cm who had received local therapy with either radiofrequency ablation (RFA) or SBRT between 2006 and 2021. A propensity score matched analysis was conducted accounting for patient demographics, facility region and tumor level characteristics, as well as an inverse probability of treatment weight-adjusted (IPTW) analysis. Overall survival was estimated using the Kaplan-Meier method. Results: We identified 14,516 patients meeting inclusion criteria, including 13,036 who received RFA and 1,480 who received SBRT. Demographic factors associated with receipt of SBRT included age >50 years, female sex, and treatment in the Middle Atlantic and East North Central regions, as well as clinical factors including larger tumor size (>3 to 5 cm), severe fibrosis/cirrhosis, and stage II disease ( p <0.05 for all). Factors associated with receipt of RFA include black race, higher Charlson-Deyo Comorbidity Scores, treatment at a comprehensive cancer program or integrated network cancer program, and treatment in the East South Central, West North Central, West South Central, Mountain, and Pacific Regions ( p <0.05 for all). Median time from diagnosis to treatment initiation was longer for those who received SBRT (66.3 vs 84.6 days, p <0.001). In a propensity matched analysis, mOS was 45.1 months for those receiving RFA vs 30.8 months for those receiving SBRT ( p <0.001). An IPTW analysis showed similar survival benefit with RFA over SBRT (mOS 51.0 vs 30.5 months, p <0.001). This OS benefit was observed in subset of patients with tumors <3cm in size. Conclusions: In this propensity matched analysis controlling for relevant patient and tumor factors, RFA was associated with improved survival. Prospective studies will be important to further analyze differences in patient outcomes.

759 Background: BRAF V600E mutations are present in 5-10% of patients with advanced colorectal cancer (CRC) and associated with poor prognosis. Recently, there was tumor agnostic FDA approval of dabrafenib + trametinib for BRAF V600E mutated solid tumors. However, the frequency of BRAF alterations ( BRAF alt), especially non-V600E, in other gastrointestinal (GI) cancers are not well described. This study characterizes BRAF alt in CRC vs other GI cancers (non-CRC). Methods: De-identified records from 51,560 patients diagnosed with GI cancers were retrospectively analyzed from the Tempus database. The molecular landscape including presence of pathogenic/likely pathogenic BRAF alt was evaluated by panel-based tissue DNA, RNA or ctDNA NGS sequencing (Tempus Labs, Inc.). The frequency of BRAF alt, co-mutations, MSI, TMB and MMR were compared between CRC and (non-CRC) by Chi-squared/Fisher’s Exact or Wilcoxon rank-sum tests. False-discovery rate correction was used for multiple testing. Results: BRAF alt were identified in 8.9% of CRC and 2.2% of non-CRC cohort. BRAF alt frequency varied by tumor type with the highest observed in colon (11%), jejunum (9.6%), intrahepatic bile duct (5.3%), rectal (4.5%), and ampulla of vater (4.5%) and lower in esophageal (0.9%) and gastric (1.6%). BRAF alt CRC had higher frequency of females (57% vs 45%, p <0.001) and older age at diagnosis (67 vs 66 yrs, p=0.029) compared to non-CRC group. Race was also significantly different, with white patients being more predominant in both groups (85% CRC,77% non-CRC). Among the BRAF alt, fusions (12% vs 2.2%, p <0.001) and amplifications (3.1% vs 0.3%, p <0.001) were higher in non-CRC vs CRC (Table). BRAF V600E was most common in all GI tumors, but higher in CRC vs non-CRC (75% vs 27%, q<0.001). Mutations higher in non-CRC vs CRC (q<0.009) included class II (G469A, K601E, BRAF-SND1, and BRAF amplification) and class III (D594N & N581S) BRAF alt. BRAF co-occurring mutations in CRC were TP53 (70%), APC (42%), RNF43 (30%), SMAD4 (22%), and PIK3CA (21%), and in non-CRC: TP53 (52%), CDKN2A (32%), CDKN2B (20%) SMAD4 (17%) and MTAP (16%). Among tissue samples, MSI-H (30% vs 4.%, p <0.001) and TMB-H ≥10 mut/MB (32% vs 6.7%, p <0.001) were more frequent in BRAF alt CRC vs non-CRC. Conclusions: Meaningful differences were found between the groups in terms of demographics, frequency, and type of BRAF alt and co-occurring mutations. In particular, certain BRAF fusions were present in a higher proportion of other GI cancers and could be an important therapeutic target for this patient population.[Table: see text]

736 Background: Patients with dMMR/MSI-H gastrointestinal (GI) cancer occasionally receive neoadjuvant immunotherapy (NIT) due to various clinical considerations. To systematically evaluate the outcome of these patients, we initiated the DREAM-GI national database, intending to harness real-world data to provide crucial insights into the outcomes, safety profile, and response patterns of dMMR/MSI-H GI cancer patients undergoing NIT. Herein, we present the initial findings. Methods: We developed a centralized database to collect de-identified clinical data from patients with dMMR/MSI-H GI cancers receiving NIT. We collected data retrospectively and prospectively through September 15, 2023. Results: The current report includes 50 patients with a median age of 67 years (range 32 to 90); 21 (42%) were female, 9 (18%) were Black, and the remaining were White. The cohort included the following tumor types- 31 (62%) colorectal, 7 (14%) gastroesophageal, and 12 (24 %) pancreaticobiliary. Most patients had localized disease (34, 68%), while the rest had oligometastatic disease. NIT consisted of pembrolizumab monotherapy in 40 (80%) patients, ipilimumab plus nivolumab in 8 (16%), and nivolumab plus chemotherapy in 2 (4%) patients. Most patients, 33 (66%), were treatment-naive. The median duration of NIT was 6 months (range: 1.5 to 55), with a time to best response of 3 months (range: 1.5 to 12). Among 47 evaluable patients, the best responses were as follows: an overall response rate of 75% (35/47), consisting of radiologic complete response (CR) in 20 (43%), pathologic CR in 4 (9%), and partial response in 11 (24%). The median progression-free survival and overall survival were not reached after a median follow-up of 14 months (range: 2-80), calculated from the date of the first immunotherapy dose to the last follow-up or death. Among 24 patients achieving CR, all remained progression-free after a median follow-up of 25.5 months (range: 3-80). Stable and progressive diseases were observed in 7 (15%) and 5 (10%) patients, respectively. Only 5 (10%) patients underwent surgery following NIT, with 4 (80%) achieving pathologic CR. The reasons for not proceeding with surgery were comorbidities in 40 (80%) patients, disease extent in 4 (8%), and patient refusal in 1 (2%). Out of the 12 patients who expired at the data cut-off, 1 was due to immunotherapy-related pneumonitis, 6 due to disease progression, and the remainder from underlying comorbidities. Conclusions: Our study underscores the remarkable response rates and durability of responses achieved with NIT in patients with dMMR/MSI-H GI cancers. Progression on NIT was infrequent. These real-world data support further investigation into non-operative approaches for patients with dMMR/MSI-H GI cancers.