Chemotherapy sensitivity and resistance testing: to be "standard" or to be individualized, that is the question.

Radical surgery with extended lymph-node dissection is the treatment of first choice and the only curative treatment for locally advanced gastric cancer. While recent combination chemotherapy with S-1 (a combination of tegafur with two biomodulators, gimeracil and oteracil) has achieved high response rates, controversy still remains regarding the significance of adjuvant cancer chemotherapy after surgery. We have been applying chemosensitivity testing in evaluating the appropriate adjuvant cancer chemotherapy for advanced gastric cancer. Our multiple studies have indicated that this chemosensitivity testing would be useful to improve the results of adjuvant chemotherapy, by increasing survivals in the sensitive group. The chemosensitivity testing is approved as "advanced clinical medicine" by the Japanese Ministry of Health, Welfare, and Labor at 11 institutes at present. While complete lymph-node dissection and chemosensitivity test-guided adjuvant chemotherapy has been reported to result in a survival benefit for patients with advanced gastrointestinal cancer, the clinical utility of the testing should be established by means of prospective, randomized clinical trials. Two pivotal clinical trials have been initiated to clarify the utility of chemosensitivity testing in the selection of the appropriate adjuvant cancer chemotherapy for gastric cancer.