LAUSR

Even though Pancreatic Ductal Adenocarcinoma (PDAC) has a 5-year survival rate of 9%, there is a minority of patients that survive more than 5 years (Long Term Survivors, LTS). Genomic studies have not shown a particular signature on those patients, suggesting the potential relevance of extrinsic non-genetic factors in survival. Also, higher number of tumor infiltrating CD8+T cells and neoantigens with similarities to microbes are predictive of better outcomes. Studies have linked microbiome with tumorigenesis and treatment responses in many cancers, including PDAC, a tumor that contains bacteria. We have analyzed intratumoral microbial content and found that LTS have higher microbial diversity and a unique microbial signature. We have also found that some of the intra-tumoral bacteria originates in the intestines. Fecal microbial transplants resulted in modulation of tumoral microbiome, immune infiltration and tumor growth. Direct bacterial immune activation or indirect effect by bacterial metabolites may be some of the mechanisms implicated. Future clinical work is needed to further understand how to modulate tumors immune status by manipulating bacteria. A clinical trial with this goal is now being developed. Citation Format: Florencia McAllister. Role of the gut-tumor microbial axis in pancreatic ductal adenocarcinoma (PDAC) [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr IA-01.