<qa>  What is the maximum dose of a combination chemotherapy?A phase III study is conducted to determine the maximum-tolerated dose MTD, dose-limiting toxicity DLT, and efficacy of a combination chemotherapy using docetaxel, cisplatin and 5-fluorouracil TPF in Pre-treated patients with metastatic esophageal cancer. The usefulness of the this regimen is evaluated by response rate, median survival time, and progression free survival. 