Analysis of DNA damage repair pathway genes as a predictive biomarker for HAIC in hepatocellular carcinoma.

e16159 Background: Hepatocellular carcinoma (HCC) is a leading cause of cancer mortality worldwide.Hepatic arterial infusion chemotherapy (HAIC) with oxaliplatin, fluorouracil, and leucovorin (FOLFOX) is one of the effective treatment for advanced HCC patients. DNA damage repaired (DDR) pathway has been widely researched in many cancers recent years, which was a promising predictive biomarker for the response to platinum-based chemotherapy and Immunotherapy. But the DDR characteristics of different subset pathways in HCC, and its correlation with HAIC efficacy were unknown. Methods: Whole exome sequencing (WES) data of 366 HCC patients was obtained from the Cancer Genome Altas (TCGA). Next generation sequencing (NGS, panel on 381/733-gene) was performed on FFPE tumor samples from 2092 Chinese HCC patients (Chinese cohort). Germ-line or somatic mutations of 32 DDR pathway genes (including Mismatch Repair and Homologous Recombination) were classified as DDR gene mutations. TMB was defined as total number of somatic non-synonymous mutations in coding region. Whole exome sequencing (WES) data and clinical data of 21 HCC advanced patients treated with HAIC were obtained to survival analysis. Results: In total, 59.84% (219/366) of HCC patients in TCGA harboring DDR mutation and 67.38% (1316/2092) in Chinese cohort. In Chinese HCC cohort, the mean TMB level of DDR mutant group was significant higher than wild-type group (mean TMB, mutation vs wild-type = 8.12 vs 6.42 Muts/Mb, P < 0.0001). The top three mutation frequency DDR genes were BRCA2 (17%), ATM (13%) and BARD1 (12%), respectively. The highest mutation frequency DDR subset pathways were Fanconi anemia (FA, 44.14%, 862/2092), homologous recombination repair (HRR, 38.71%, 756/2092) and check point factors (CHP, 17.31%, 338/2092) come in second and third, respectively. Next we compared the TMB level between different DDR subset pathways, the mutant of nucleotide excision repair (NER) pathway harbored the highest medium TMB level (7.26 Muts/Mb). The survival analysis was performed on HCC patients treated with HAIC with FOLFOX. There was no difference in clinical baseline information between DDR mutation group (n = 6) and wild-type group (n = 15). The progression-free survival (PFS) of DDR mutation group were significantly longer than wild-type group (median PFS, mutation vs. wild-type = 8.9 vs. 4.5 months; HR 0.34[95% CI 0.13-0.85]; P = 0.0349), and an extending trend on overall survival (OS) without significant difference (median OS, 15.7 vs 8.9 months; HR 0.37[95% CI 0.13-1.00]; P = 0.0921). Conclusions: The DDR pathways was associated with higher TMB level. Preliminary data from clinical cohorts suggested better treatment outcomes of HAIC with FOLFOX in DDR mutation HCC patients.