TYMS and esophageal cancer: However, we did not observe any strong association between the tested genotypes and tumor response, except a trend reflective of potential associations for XRCC1 and MDR1. Similar negative results have been reported from retrospective analyses of TYMS and non-TYMS genotypes in relation to the histopathological tumor responses in patients with gastric and esophageal cancers [39], [41], [49].