Presence of RB1 or Absence of LRP1B Mutation Predicts Poor Overall Survival in Patients with Gastric Neuroendocrine Carcinoma and Mixed Adenoneuroendocrine Carcinoma.

Purpose: Neuroendocrine carcinomas (NECs) of the stomach are extremely rare, but fatal. However, our understanding of the genetic alterations in gastric NECs is limited. We aimed to evaluate genomic and clinicopathological characteristics of gastric NECs and mixed adenoneuroendocrine carcinomas (MANECs).

Materials and methods: Fourteen gastric NECs, 3 gastric MANECs, and 1381 gastric adenocarcinomas were retrieved from the departmental next-generation sequencing database between 2017 and 2019. Clinicopathological parameters and next-generation sequencing test results were retrospectively collected and reviewed.

Results: Gastric NECs and MANECs frequently harbored alterations of TP53, RB1, SMARCA4, RICTOR, APC, TOP1, SLX4, EGFR, BRCA2, and TERT. In contrast, gastric adenocarcinomas exhibited alterations of TP53, CDH1, LRP1B, ARID1A, ERBB2, GNAS, CCNE1, NOTCH, and MYC. Mutations of AKT3, RB1, and SLX4; amplification of BRCA2 and RICTOR; and deletion of ADAMTS18, DDX11, KLRC3, KRAS, MAX, NFKBIA, NUDT7, and RB1 were significantly more frequent in gastric NECs and MANECs than in gastric adenocarcinomas. The presence of LRP1B mutation was significantly associated with longer overall survival (OS), whereas RB1 mutation and advanced TNM stage were associated with shorter OS.

Conclusion: We identified frequently mutated genes and potential predictors of survival in patients with gastric NECs and MANECs.