Capecitabine is a newly designed oral fluoropyrimidine carbamate which is converted to 5FU in three steps, the first step is catalysed by carboxyl esterase located almost exclusively in the liver, the second step by cytidine deaminase expressed in the liver and various types of tumours, and the last by TP which is higher in tumours than in normal tissues thus ensuring an enhanced efficacy (Miwa et al, 1998). The gene discussed is CDA; the disease is neoplasm.