In a study of 94 cancer patients, De Luca et al., 47 showed that the detection of rare DPYD variants (MAF < 0.05) by exon sequencing resulted in a 2.5% improvement in the identification of patients with DPD deficiency, compared to screening only the four recommended DPYD variants, which identified 20% of DPD-deficient patients. Here, DPYD is linked to dihydropyrimidine dehydrogenase deficiency.