DPYD and dihydropyrimidine dehydrogenase deficiency: Confirmation of impaired DPD activity in homozygous carriers of rs72728438 would be of paramount importance; considering that in our sample cohort, the GG genotype was present in 5/40 (12.5%) of PM subjects and no other no-function variants were detected in such subjects, the validation of this marker could drastically improve the genotype-based prediction of DPD deficiency.