TYMS and metastatic neoplasm: In metastatic disease, low TS levels have consistently been found to be predictive of responsiveness to 5-FU-based chemotherapy (Peters et al, 1994; Johnston et al, 1995; Kornmann et al, 1997; Leichman et al, 1997, Leichman, 1998; Lenz et al, 1998; Aschele et al, 1999; Bathe et al, 1999; Cascinu et al, 1999; Paradiso et al, 2000; Allegra, 2002).