Chemotherapy for colorectal cancer patients is divided into adjuvant chemotherapy after radical surgery, neoadjuvant chemotherapy for some locally advanced stages, and chemotherapy regimens for patients with advanced stages. For the selection of adjuvant chemotherapy, there are the following factors to be referred: For stage 2 colorectal cancer, adjuvant chemotherapy is recommended if accompanied by high-risk factors (number of cleared lymph nodes less than 12, nerve invasion, choroidal carcinoma embolism, preoperative obstruction, perforation, positive cut margins, and poor histological differentiation (excluding high instability of microsatellite). Chemotherapy regimen for this group of patients: single agent oral capecitabine is recommended, usually for six months. Studies have shown that for patients with stage 2 with high-risk factors, adding oxaliplatin to single-agent fluorouracil does not provide a survival advantage, but increases chemotherapy side effects. However, it is reasonable to recommend the combination chemotherapy regimen FOLFOX (oxaliplatin + calcium folinate + fluorouracil) for stage 2 colorectal cancer combined with multiple high-risk factors. Colorectal staging pattern diagram For stage 3 colon cancer (patients with lymph node metastasis), postoperative adjuvant chemotherapy with a standard chemotherapy duration of six months is warranted. However, according to the latest research, and also written in the treatment guidelines (NCCN guidelines), for patients with low-risk stage III colon cancer (stage pT1-3N1) adjuvant chemotherapy for three months survival prognosis is not worse than chemotherapy for six months. In terms of specific chemotherapy regimens, the 3-month XELOX (intravenous oxaliplatin + oral capecitabine) regimen was not worse than 6-month chemotherapy in terms of recurrence-free survival, but similar conclusions were not obtained for the FOLFOX regimen. However, for patients with high-risk stage III colon cancer (stage T4N1-2 or TanyN2), studies have shown that the 3-month FOLFOX regimen is inferior to 6-month chemotherapy in terms of recurrence-free survival, but no similar conclusions were obtained for the application of the XELOX regimen. Overall, for patients with high-risk stage III colorectal cancer, both the XELOX and FOLFOX regimens are currently recommended to be given with standard six-month adjuvant chemotherapy. Neoadjuvant chemotherapy regimen for some patients with locally advanced or potentially resectable solitary hepatopulmonary metastases: For patients with locally advanced tumors, such as invasion of neighboring organs or tissues, or potentially resectable distant metastases, 2-3 cycles of neoadjuvant chemotherapy can be administered first, followed by review and evaluation of the results to assess whether radical surgery is possible. Neoadjuvant chemotherapy regimens are generally similar to postoperative adjuvant chemotherapy regimens, commonly the XELOX regimen or FOLFOX regimen. If the chemotherapy is effective, the patient is converted to radical surgery and the original regimen is continued after surgery. If the tumor does not shrink and chemotherapy is ineffective, a change of chemotherapy regimen is required, along with combination of targeted drug therapy. Chemotherapy regimen for patients with advanced diagnosis, inoperable or no potential surgical opportunity: For this group of patients, there is basically no chance of radical surgery. The aim of treatment is to achieve a tumor-free state and prolong patient’s survival as much as possible through drug therapy, combined with necessary local treatment (radiofrequency ablation or interventional therapy or cryotherapy). At the beginning of treatment, it is recommended to improve the genetic testing of KRAS/NRAS/BRAF/HER-2 and select the appropriate targeted drugs according to the genetic mutations. For this group of patients, the following treatment options are recommended: FOLFOX regimen combined with cetuximab or panitumumab (for KRAS/NRAS wild type only); or XELOX chemotherapy regimen combined with bevacizumab; or FOLFIRI regimen (irinotecan + fluorouracil + calcium folinic acid) combined with bevacizumab for patients in good health. For patients who are too weak to tolerate combination chemotherapy and targeted therapy, fluorouracil or capecitabine or irinotecan are recommended as single agents. With common chemotherapy regimens: (1): Single-agent oral capecitabine (3-week regimen) Based on body surface area, general height and weight, 850-1250 ml/m2, twice a day, orally half an hour after meals in the morning and evening, for 14 consecutive days orally, stopping for 7 days, for one cycle. It is recommended to complete 8 cycles. (2): XELOX regimen (also called Capeox regimen) (3-week regimen): intravenous oxaliplatin, 130 mg/m2 body surface area, day 1, oral capecitabine, 1000 mg per m2 body surface area, days 1-14, stopping for 7 days for one cycle. (3): FOLFOX regimen (2-week regimen): This regimen is a systemic intravenous infusion with no oral chemotherapeutic agents. Specific dosing: Oxaliplatin 85mg per square meter, day 1, intravenous drip; L-calcium folinic acid, 400mg per square meter, day 1, intravenous drip; 5-FU, 400mg per square meter, day 1, intravenous push; 5-FU, 2400mg per square meter, continuous pump 46-48 hours