Antitumor effect of paclitaxel for gastric cancer is AUC dependent

Paclitaxel (PTX), which is used for ovarian cancer, lung cancer, breast cancer and gastric cancer, is administered at a dose of 210 mg/m(2) once every three weeks. However, WHO grade 3-4 hematological and non-hematological toxicity occurred frequently in this manner. In recent studies about ovarian cancer and lung cancer, a schedule in which PTX was given weekly could have the same or better efficacy, with fewer side effects. The response rate of PTX administered every three weeks for gastric cancer, was 23.3 to approximately 28.0%, while that of PTX administered weekly was 24.0 to approximately 25.8%. Because of fewer adverse events, weekly PTX is widely used for gastric cancer in Japan. To prove the validity of PTX weekly administration, we performed a study using six specimens removed surgically and one specimen collected from ascites. A chemosensitivity test was performed on the basis of two assumptions: a high concentration for a short time, and a low concentration for a long time. A similar PTX effect was obtained when the AUC was equal. In this study, we demonstrated that the effect of low-dose PTX was equal to the effect of high-dose PTX in gastric cancer.