Prediction of the effect of capecitabine in gastric cancer by immunohistochemical staining of thymidine phosphorylase and dihydropyrimidine dehydrogenase

The objective of this study was to investigate the relationship between the expression of thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) and the response to capecitabine in patients with advanced/recurrent gastric cancer. TP and DPD expression in paraffin-embedded specimens of primary lesions, obtained from 25 patients before capecitabine chemotherapy, were evaluated by immunohistochemical staining with anti-TP and anti-DPD monoclonal antibodies. The patients (19 male and six female) had a median age of 65 years (range 37-74). All had a good performance status [Eastern Cooperative Oncology Group (ECOG) 0 or 1]. Overall response rate to capecitabine therapy was 32%. TP was positive in 19 tumors (76%) and DPD was positive in 13 tumors (52%). The response rate (RR) was significantly higher (Fisher's exact test, P=0.028) in patients with TP-positive and DPD-negative tumors (RR=60%, 6/10) than in the remaining patients (RR=13%, 2/15). TP and DPD expression profiles are useful for predicting a response to capecitabine.