Previous studies, reviewed elsewhere [57,130], have indicated the potential association between response to nCRT in rectal cancer and SNPs in several genes including TS, EGFR, epidermal Growth Factor (EGF), coiled-coil protein DIX1 (CCD1), superoxide Dismutase 2 (SOD2), IL13, 8-oxoguanine DNA glycosylase (OGG1) and methylenetetrahydrofolate reductase (MTHFR). The gene discussed is MTHFR; the disease is rectal cancer.