The chemotherapy interval and the number of chemotherapy cycles vary according to different chemotherapy regimens for rectal cancer, such as the common clinical CF (calcium folinic acid for injection) plus fluorouracil regimen, which is usually repeated once every 4 weeks, probably using about 6 weeks, i.e. 6 cycles; the two more common chemotherapy regimens, FOLFOX and FOLFIRI, are usually repeated once every 2 weeks in the clinic, probably requiring 12 cycles. The interval of chemotherapy for patients taking oral Siroda is approximately 3 weeks repeated. Patients with bowel cancer are treated with multiple chemotherapy cycles, and before each chemotherapy treatment, blood routine, liver and kidney function, cardiopulmonary function tests, etc. should be tested, and then patients should be evaluated, and they also need to be tested regularly after the chemotherapy treatment is finished, so as to minimize the harm of chemotherapy side effects occurring to patients.