How many days is a cycle of cancer chemotherapy?

Different chemotherapy regimens may be selected for different tumors and different chemotherapy drugs. Generally, the doubling time of tumor cells is 21 days, so chemotherapy regimens are often selected for 21-28 days. For esophageal cancer, chemotherapy is often performed once a week, cisplatin is used, and gemcitabine or paclitaxel is used once a week. If capecitabine is used for chemotherapy, the chemotherapy regimen is to choose to take the drug for 14 days, then rest for 1 week, and then continue to take it for another week.