Decafloxuridine is one of the most studied antiproliferative oligomers showing a potent antitumoral activity in leukemias, glioblastoma and colon cancer [74] by inhibition of thymidylate synthase and DNA topoisomerase [75,76] with lower toxicity than FU as the formation of the toxic α-fluoro-β-alanine metabolite [77] is highly reduced compared with the use of FU [78]. The gene discussed is TYMS; the disease is colonic neoplasm.