Moreover, we showed that the low methylation levels of cg sites (cg02269161, cg03226737, cg08185661, cg16437728, cg18560328, cg22723056, and cg24678137) of SYT9 were associated with an unfavorable PFS (P < 0.001, P = 0.044, P = 0.002, P = 0.015, P = 0.004, P = 0.028, and P = 0.005, respectively) (Figure 7(a–f) and 7(g)), whereas other methylation cg sites (cg08913010, cg14243481, and cg26945996) were not associated with a prognostic value for GC patients (P = 0.564, P = 0.075, and P = 0.122, respectively) (Figure S7D, S7E, and S7F). This evidence concerns the gene SYT9 and gastric cancer.