Unique action determinants of double acting topoisomerase inhibitor, TAS-103

Challenge for a better combination with basic evidence

5-Fluorouracil (5-FU) has been the most widely accepted and studied chemotherapeutic agent, and many combination chemotherapeutic regimens have been reported. However, until recently, a standard regimen for metastatic gastric cancer had not been established. The combination of S-1 and cisplatin is a good candidate as a standard first-line regimen for metastatic gastric cancer. On the other hand, interest in biochemical modulation has become wide spread recently. The low level of dihydropyrimidine denhydrogenase (DPD), thymidylate synthase (TS) activities, and a high level of orotate phosphoribosyl-transferase (OPRT) activity enhance the antitumor effect of 5-FU and S-1. Docetaxel is one of the agents that modulate these enzyme expressions and activities. Moreover, the response rate of combination therapy of docetaxel and S-1 for metastatic gastric cancer was 56.3% and median survival time was 14.3 months in a phase II study, showing it to be a good candidate for a new standard regimen for gastric cancer. A phase III collaborative study, START (S-1 and Taxotere for advanced gastric cancer randomized phase III trial), is now under way in Japan and Korea.

Future prospects of personalized chemotherapy in gastric cancer patients: results of a prospective randomized pilot study

In the present study, in order to evaluate the feasibility of personalized chemotherapy, a prospective randomized pilot study was performed in 30 advanced or recurrent gastric cancer patients. As we have demonstrated previously, the expressions of mRNA from tumor biopsy samples for seven molecular markers, i.e., dihydropyrimidine dehydrogenase (DPD), glutathione S-transferase (GST)-pi, beta-tubulin (tub), O6-methylguanine-DNA methyltransferase (MGMT), multiple drug-resistant protein (MRP)-1, NADPH/quinone oxidoreductase (NQO)-1, and cytochrome p450 (P450), were examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis and therapy was recommended in a flow chart that depended on the level of expression of these predictive molecular markers. We chose 12 therapeutic plans, including best supportive care (BSC). We treated 15 patients according to the gene expression profiles, and the remaining 15 patients (controls) were treated without recommended regimens, and the therapy was continued after the expression profiles were checked. Interestingly, 11 of 26 lesions (42.3%) responded after treatment given according to gene expression analysis; however, no clinical response was detected in the control group. The prediction of the response, including resistance, was successful in 75.9% by the gene expression profiles. Moreover, the survival of the patients with the recommended treatment was better than that of patients without a recommended protocol. These results indicate that personalized treatment may be beneficial for gastric cancer chemotherapy and further randomized trials should be carried out in the future.