DNA damage repair (DDR) gene mutations (mut) are predictors of response to platinum-based chemotherapy in advanced pancreatic cancer (PC) patients (pts)

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Background: Somatic DDR mut have been reported in close to 10% of PC samples. In this study we investigate their predictive value for response to platinum-based chemotherapy. Methods: Case-control study with pts deriving response to oxaliplatin-based treatment (partial or complete response at any line) [n = 30] versus no response (progression in first restaging at 1st line) [n = 18]. An in-house NGS panel test of 420 genes was performed on tumor samples. DDR mut were classified in 2 subgroups: (a) functional BRCA1, BRCA2 or PALB2; and (b) any functional DDR gene mut, including those in (a). Results: 48 pts were included, median ages was 54.5 years (30-74), 29 male, 26 were diagnosed with stage IV, 36 pts (75%) received FOLFIRINOX and 37 received platinum-based chemotherapy as 1st. line treatment. Prevalence of DDR mut are described in the table. Among responders, 3 tumors had BRCA2 mt, 3 BRCA1, 2 ATM, and 1 each with BRCA2 + MSH2, PALB2, PMS2, MUYTH, RECQL4 + MDC1. Among non-responders 1 tumor each had ATM, FANCD2 and BLM. Median progression-free survival (PFS) with oxaliplatin-based chemotherapy in pts with BRCA1, BRCA2 or PALB2 mut tumors was 21.7 months (95% CI 12.3-NA); among those with any DDR mt was 12.3 months (95% CI 9.13-NA); while in pts whose tumors had no DDR mut was 6.4 months (95% CI 3.07-13)(Log-rank P-value = 0.02 comparison subgroup [a] vs. others; P-value = 0.1 subgroup [b] vs. others). Conclusions: The subgroup of pts with PC whit tumors harboring DDR gene mut, particularly functional BRCA1, BRCA2 or PALB2, have higher response rate and longer PFS with oxaplatin-based chemotherapy. [Table: see text]