Molecular subtyping of 90 gastric tumor tissues from these patients post-radiotherapy revealed that in 6 MSI-positive samples (6.7%), 3 had MLH1 promoter methylation, 2 had double somatic mutations in MMR genes, and 1 had a homozygous deletion involving MLH1 gene that was found in the tumor sample, but not in normal tissue. This evidence concerns the gene MLH1 and gastric neoplasm.