TYMS and Decreased total leukocyte count: Two studies found no significant genetic type was observed in conjunction with TS polymorphism [21,27]; but Goekkurt et al. reported that carriers of at least one 3R haplotype were at lower risk for developing grade 3/4 leukopenia with an OR of 0.12 (95% CI: 0.02-0.88) [31].