[A case of recurrent gastric cancer showing partial response to capecitabine/CDDP after treatment with S-1/CDDP].

S-1 and capecitabine are orally administered fluoropyridines reported to be effective in the treatment of advanced gastric cancer(AGC). In fact, both S-1/CDDP and capecitabine/CDDP are considered to be the standard first-line treatments for AGC.However, no information concerning on the activity of capecitabine in S-1-pretreated patients with AGC has been reported. Here, we present a case of recurrent gastric cancer that showed a partial response resulting in 6 months of progres-sion-free survival, thanks to capecitabine/CDDP after the failure of multiple anticancer drugs such as S-1/CDDP. S -1 and capecitabine may exhibit cross-resistance because they both have the same final active metabolite: 5-fluorouracil(5-FU). Dihydropyrimidine dehydrogenase(DPD)is the rate-limiting enzyme in the degradation of 5-FU, and S-1 contains the inhibitor of DPD. Thus, S-1, but not capecitabine, is active against tumors with high DPD expression. On the other hand, capecitabine is activated to 5-FU by thymidine phosphorylase(TP)within the tumor tissue and is more effective against tumors with high TP expression. The present case suggests that S-1 and capecitabine do not always exhibit cross-resistance, and that capecitabine may be effective in S-1-pretreated patients with AGC.