Palmar-plantar erythrodysesthesia in patients receiving capecitabine and intratumor thymidine phosphorylase and dihydropyrimidine dehydrogenase: is there a pharmacologic explanation?

Background: Palmar-plantar erythordysesthesia (PPE) is the most common toxicity of capecitabine. Preclinical studies have shown that radiation therapy (RT) upregulates thymidine phosphorylase (TP), which could in turn increase the efficacy of capecitabine. Capecitabine is degraded by dihydropyrimidine dehydrogenase (DPD), and a deficiency in this enzyme can increase the toxicity of capecitabine.