The results revealed that C5aR1 expression was enhanced in GC tissues compared to normal gastric tissues, and that patients with high expression of C5aR1 had a worse 10-year overall survival compared to those showing low expression of C5aR1. Functional analysis revealed that C5aR1 is a gene related to the immune system and may play a crucial role in inflammatory and tumor immune responses. The gene discussed is C5AR1; the disease is neoplasm.