Cros, Jerome F.

ABSTRACT This international, multidisciplinary consensus report represents the first effort to systematically define and characterize fatty pancreas. A key outcome of this endeavor was the recommendation to adopt “fatty pancreas” as the standardized and inclusive term to describe all forms of fat accumulation in the pancreas. This terminological consensus provides a critical foundation for unified reporting and clinical communication. Another major contribution of the report is the consensus on diagnostic imaging findings, which was based on radiological and endoscopic modalities. The proposed criteria aim to enhance consistency in clinical assessment and support the development of standardized research protocols. In addition to establishing terminology and diagnostic frameworks, the report also synthesizes current knowledge across a wide range of relevant domains. These include the etiology and epidemiology of fatty pancreas, as well as its associations with alcohol consumption, smoking, acute and chronic pancreatitis, pancreatic exocrine insufficiency, type 2 diabetes mellitus, and surgical outcomes. The potential links between fatty pancreas and neoplastic conditions such as intraductal papillary mucinous neoplasms and pancreatic cancer are also addressed, alongside the current understanding of its metabolic implications (beta‐cell function and glucose homeostasis) and treatment strategies. Throughout the consensus process, a consistent theme emerged: the limited availability of high‐quality, prospective clinical data. Therefore, many of the recommendations in this report are based on expert consensus rather than strong empirical evidence. As such, the statements require rigorous prospective validation before they can be adopted into routine clinical practice. This underscores a critical need for further research, particularly studies aimed at clarifying causal relationships, validating diagnostic tools, and determining the clinical relevance of fatty pancreas across diverse patient populations. This report serves as both a summary of our current understanding and a roadmap for future investigations, aiming to close existing knowledge gaps and guide evidence‐based clinical practice in this emerging field.

662 Background: Alkylating-based chemotherapy (ALK) is one of the main treatments used in patients with advanced pancreatic neuroendocrine tumors (PanNETs). Its use has been associated with an increased risk of grade progression and acquisition of a hypermutator phenotype, associated with frequent alterations of the mismatch repair (MMR) genes. This suggests a potential benefit of immune checkpoint inhibitors (ICI) that are otherwise ineffective in ALK-naïve PanNETs, which are mostly hypomutated. We aimed to describe the efficacy of ICI in patients with advanced PanNET pretreated with ALK. Methods: We assembled an international retrospective cohort of patients with advanced PanNET who received at least one cycle of ICI, and who had previously received at least 3 months of ALK. Patients with poorly-differentiated neuroendocrine carcinoma were excluded. The primary endpoint was progression-free survival (PFS) and the secondary endpoint was the objective response rate (ORR). The impact of tumor mutational burden (TMB, high being defined by >10 mut/Mb) and MMR alterations (mutations or IHC) was explored. Results: We included 39 patients (median age 58.7, male sex 62%). All PanNETs were progressive at baseline and presented a median of 3 (IQR, 2-4) metastatic sites. Tumors were predominantly classified as G2 (47%) or G3 (42%), with a median Ki-67 of 18.5% (IQR, 12-35). 23/27 patients with tumor tissue or ctDNA NGS testing had high TMB (median, 35 mut/Mb; IQR, 24-106) and 12/22 had MMR alterations. Patients had previously received an average of 14 cycles (IQR, 7-25) of ALK (temozolomide 78%, streptozotocin 18%, dacarbazine 4%), which had yielded objective response in 72% of cases. In addition, patients had received a median of 4 (IQR, 3-5) other treatments (including platinum drugs in 80% and PRRT in 51%). ICI mainly consisted in an anti-PDL1/PD1 + anti-CTLA4 combination (85%) or a monotherapy (15%), with a median of 3 (IQR, 2-8) cycles. The ORR was 18% and the disease control rate was 46%. Median PFS was 2.8 months (95% CI, 0.62-4.96) and 6-month PFS rate was 31%. 19% of patients had grade 3-4 toxicity. Patients with high TMB had higher ORR (30% vs. 0%, p=0.03) and longer median PFS (4.9 vs. 2.1 months, p=0.004) compared with patients with low/unknown TMB. Patients with altered MMR had higher ORR (42% vs. 7%, p=0.02) and longer median PFS (8.9 vs. 2.5 months, p=0.014) compared with patients with no/unknown MMR alterations. Conclusions: While ICI shows limited efficacy in unselected patients with advanced PanNETs pretreated with ALK, it may be an effective treatment option in case of high TMB and MMR alterations.