Genetic Characteristics Of Pannets, Rectal Nets, Thoracic Nets And Its Correlation With Efficacy Of Chemotherapy

Background: Neuroendocrine tumors (NETs) are clinical heterogeneous. To date, no studies have focused on the genetic characteristics of NETs at different anatomical sites in the Chinese cohort. We aim to explore the genetic similarities or differences between NETs at different sites, and evaluate the predictive indicators of chemotherapy based on Temozolomide. Methods: The patients were from a prospective clinical study STEM (from a single institute, NCT03204032, NCT03204019). This cohort included 47 patients with NETs, including 14 Pancreatic NETs (PanNETs), 11 Rectal NETs, 14 Thoracic NETs, and 8 Others. Whole exome sequencing (WES) was performed. Results: A total of 76,057 somatic mutations were detected in 16,510 genes. The median tumor mutation burden (TMB) was 13.4, 10.5, 11.0 and 11.9 in PanNETs, Rectal NETs, Thoracic NETs and Others, respectively. After sequencing depth filtering, they were 3.5, 3.9, 3.3 and 3.6, respectively. Low intra-tumoral heterogeneity (ITH) was observed in NETs. The median ITH index was 2, 2.5, 2.5 and 2 in PanNETs, Rectal NETs, Thoracic NETs and Others, respectively; the median Shannon diversity index (SDI) was 0.23, 0.13, 0.23 and 0.24, respectively. The driver gene mutations varied in NETs at different sites. The recurrently mutated driver genes were MEN1, ATM, TSC2, PLXNB2, MUC6, AMER1 and USP9X for PanNETs; APC, APOB and FAT1 for Rectal NETs; KMT2B and CACNA1A for Thoracic NETs. Copy number analysis showed that copy number loss frequently occurred in all NETs. The median copy number variation burden (CNV burden) was 34.0, 10.9, 16.1 and 11.6 in PanNETs, Rectal NETs, Thoracic NETs and Others, respectively. The CNV burden of PanNETs was higher than others. Based on the results of CNVs, NETs at different sites could be distinguished by linear discriminant analysis (LDA). We analyzed the correlation between genetic characteristics and progression-free survival (PFS). As a result, NETs with higher TMB (\u003e10 /Mb, P=0.043) or higher CNV burden (\u003e20, P=0.047) showed statistically longer PFS. More patients should be included to find a correlation between genetic characteristics and PFS. Conclusions: NETs at different sites harbored different somatic driver mutations, and copy number loss was widespread in NETs. NETs with higher TMB or higher CNV burden showed statistically longer PFS. Citation Format: Yihebali Chi, Weili Liu, Lijie Zuo, Yuehua Wang, Weijing Cai, Susheng Shi, Yanying Ge, Rui Li, Lijie Song, Yiqi Yang, Zheng Liu, Xiaowu Dou, Hong Zhao. Genetic characteristics of PanNETs, Rectal NETs, Thoracic NETs and its correlation with efficacy of chemotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4743.