Outcomes in Pancreatic Adenocarcinoma (PDA) Patients (pts) with Genetic Alterations in DNA Damage Repair (DDR) Pathways: Results from the Know Your Tumor (KYT) Program.

191 Background: Up to 17% of PDAs harbor mutations in the DDR pathway. However, the purely prognostic relevance of these mutations is unclear. Furthermore, outcomes in response to platinum-based therapies in PDA pts harboring mutations in a broad range of DDR genes, particularly beyond BRCA1/2 and PALB2, remain unexplored. Methods: We evaluated PDA pts enrolled in the KYT registry for whom we collected cancer related exome sequencing and clinical outcomes. Pts were categorized as resected and advanced (LAPC and metastatic pts), and tumor genomic profiles were categorized as DDR mutated (DDRmut) based on the presence of pathogenic alterations in BRCA1/2, PALB2 (Group 1), ATM, ATR, ATRX (Group 2), or BAP1, BARD1, BRIP1, CHEK1/2, RAD50/51/51B, or FANCA/C/D2/E/F/G/L (Group 3). Tumors harboring no DDR mutations were labelled DDR proficient (pDDR). Median overall survival (OS) was measured from the date of diagnosis until death. Results: The OS was similar in all resected pts, irrespective of exposure to platinum therapy (see Table). However, for the pts with advanced disease, OS was significantly longer for DDRmut vs. pDDR pts, particularly in the platinum-treated group; but no such difference was identified in the platinum-naïve pts. Detailed outcomes for the 3 Groups will be presented, but in general the OS in pts with mutations in all 3 DDRmut Groups was greater than for the pDDR pts; but again this difference was lost in the platinum-naïve pts. Conclusions: Advanced DDRmut pts have an improved OS when treated with platinums, compared to pDDR pts. But, in the absence of platinum-based therapy, there is no OS difference observed in DDRmut vs. pDDR pts, suggesting that DDR status has no pure prognostic value. These findings support the need to test all pts with advanced PDA, to ensure that DDRmut pts are treated with platinum-based therapy. [Table: see text]