Colorectal cancer, as one of the most common tumors in China, has been on the rise in recent years. Surgery is still the only means of cure, but half of the patients face the problem of recurrence and metastasis. Adjuvant treatment for colorectal cancer Adjuvant treatment after colorectal cancer surgery includes adjuvant chemotherapy and adjuvant radiotherapy. The ultimate goal of adjuvant therapy is to eliminate the remaining micro-metastatic lesions, reduce the chance of tumor recurrence and metastasis, and improve the cure rate. Adjuvant chemotherapy: Surgery is the only radical treatment for stage I-III colorectal cancer, but 35%-50% of patients still experience tumor recurrence after radical surgery. The results of numerous clinical studies have confirmed that adjuvant chemotherapy with 5-fluorouracil alone combined with the sensitizer calcium folinic acid after radical surgery reduces the risk of early recurrence of colorectal cancer by about 40% and improves overall survival by about 7%. Studies have also confirmed the equivalence of oral fluorouracil analogs (e.g., capecitabine) to intravenous 5-fluorouracil, and capecitabine is becoming more widely used in clinical practice because of the convenient mode of administration and good tolerability of oral drugs. On top of single-agent fluorouracil-based therapy, two-drug chemotherapy in combination with oxaliplatin can further improve overall survival by 3.0%. Therefore, adjuvant chemotherapy after radical surgery for colon cancer can effectively reduce the recurrence rate and extend the overall survival of patients. However, not all patients with colon cancer need to receive adjuvant chemotherapy after radical surgery. Stage I colon cancer has early tumor stage and high cure rate, and the 5-year survival rate of patients who underwent radical surgery alone is over 90%, so adjuvant chemotherapy is not recommended; stage IV colon cancer, except for a small number of patients with resectable liver and/or lung metastases, about 85% of patients lose the opportunity to undergo radical surgery, and this group receives palliative chemotherapy, which does not meet the definition of adjuvant chemotherapy. Therefore, the indications for adjuvant chemotherapy are limited to patients with stage II and stage III colon cancer. All patients with stage III colon cancer are recommended to receive adjuvant chemotherapy. There is some controversy whether stage II colon cancer patients should receive adjuvant chemotherapy or not. Currently, it is recommended to divide stage II colon cancer into two categories based on the combination of high-risk recurrence risk factors: high-risk stage II and non-high-risk stage II, and adjuvant chemotherapy is recommended for stage II colon cancer with high-risk factors, while stage II colon cancer without high-risk factors is recommended to be followed up or given with single-agent fluorouracil drugs, including 5-fluorouracil alone combined with calcium folinic acid or capecitabine adjuvant chemotherapy. According to the “Colorectal Cancer Diagnosis and Treatment Standards” of China’s Health and Family Planning Commission, high-risk factors include poor histological differentiation (grade III or IV), T4 stage in TNM staging, invasion of blood vessels and/or lymphatic vessels, preoperative combined intestinal obstruction and/or intestinal perforation, and insufficient lymph nodes (less than 12) detected in surgical resection specimens; the National Comprehensive Cancer Network (NCCN), which is widely recognized internationally. In the National Comprehensive Cancer Network (NCCN) guidelines, the risk factors for stage II colon cancer also include tumor invasion of nerves, positive tumor margins, suspicious positive tumor margins, or too close to the tumor. Adjuvant radiotherapy: In colon cancer, postoperative radiation therapy is generally not performed unless there is clear tumor invasion of local organs. As for rectal cancer, because even for radical surgery, the local recurrence rate can still be as high as 20-30%. Especially for rectal cancer of the lower and middle segments, the tumor is usually located below the peritoneal reflex, and due to the special anatomical structure of the rectum, radiotherapy has become an important part of comprehensive perioperative treatment. Therefore, the current NCCN guidelines recommend that adjuvant radiotherapy should be considered if the postoperative pathological stage is T3 or above or lymph node metastasis (+). Although most clinical studies on adjuvant radiotherapy for rectal cancer have shown that radiotherapy does not significantly prolong the survival time of patients, it can significantly reduce the risk of local recurrence to 5-7%. Therefore, if there is no obvious contraindication to radiotherapy or the patient explicitly refuses, radiotherapy should be given to the primary site for both stage II and III rectal cancer. In addition, with the rapid development of medical imaging, pelvic-enhanced MRI and rectal endoluminal ultrasound can perform preoperative staging more and more accurately, so for rectal cancer with preoperative diagnosis of T3/T4 or N+, the current international guidelines advocate preoperative neoadjuvant radiotherapy. However, due to the varying medical standards and cultural differences in China, it will take time to fully promote preoperative neoadjuvant radiotherapy for low to intermediate rectal cancer. Notes on adjuvant therapy: There is no definite time to start adjuvant chemotherapy, in principle, it can be started as long as the patient’s physical condition can tolerate it, mostly 4-8 weeks after radical surgery; the whole adjuvant therapy time frame usually does not exceed 6 months. For elderly colon cancer patients aged >70 years and other patients with complicated concomitant diseases should be given combination chemotherapy, single-agent fluorouracil-based chemotherapy or regular follow-up under the guidance and close monitoring of a specialist. The use of irinotecan (CPT-11), the molecularly targeted drug bevacizumab, and cetuximab as adjuvant therapy is not currently recommended for patients with high-risk stage II and III colorectal cancer. In addition, local radiotherapy should also be given electively if preoperative radiotherapy has not been given for low and intermediate rectal cancer, and in principle, adjuvant radiotherapy should be started within 3 months after surgery. Simultaneous administration of oral capecitabine and 5-Fu sensitization can be considered at the time of radiotherapy. Overall, adjuvant therapy has been shown to reduce the risk of local recurrence and distant metastasis in colorectal cancer and prolong overall survival. However, a reasonable comprehensive management plan should also be designed for each individual patient under the guidance of a multidisciplinary team after a comprehensive assessment of the benefits and risks of patients receiving adjuvant radiotherapy. Rehabilitation of colorectal cancer The postoperative rehabilitation of colorectal cancer patients mainly includes physiological rehabilitation and psychological rehabilitation. Physiological aspects: Due to permanent changes in the anatomical structure of the patient’s digestive tract, there will be significant changes in eating and defecation habits. For example, adhesional intestinal obstruction is likely to occur within 6 months after surgery, so the diet usually tries to choose nutritionally balanced and easily digestible food as much as possible. In addition, due to partial resection of the large intestine, many patients have more frequent and diluted bowel movements, while some patients may experience alternating diarrhea and constipation because the peristaltic function of the intestine has not fully recovered. The vast majority of patients will return to a normal diet and bowel habits within a year. In addition, some patients may have a temporary or permanent stoma in the abdomen according to their condition. Stoma bag replacement and routine stoma care are important aspects of a smooth postoperative recovery. Patients and their families should learn how to change the stoma bag, care for the stoma and the skin around the stoma, and observe the exhaustion and defecation under the guidance of a professional stomatologist. Patients undergoing postoperative adjuvant radiotherapy should also be aware of the associated GI reactions during treatment. If there is significant weight loss, loss of appetite, or severe diarrhea during treatment, treatment should be suspended, and timely communication with oncologists should be made to adjust the treatment plan and dose, as well as to enhance supportive therapy. Psychological aspect: When patients learn that they are suffering from malignant tumor, the psychological shock is huge, and they may have various bad emotions such as irritability, anxiety, insomnia, depression and frustration. In addition to the support and encouragement from family members, it is also very necessary to ask professionals for psychological counseling and psychological guidance at the right time. Psychologists can help patients to vent their bad emotions correctly through counseling, physical or pharmacological means, which can help to increase patients’ confidence in curing the disease and also help to cooperate with doctors to carry out anti-tumor treatment more actively. In particular, we should pay attention to patients who cannot retain their anal function because of their condition. The artificial anus (stoma) can have a great impact on the patient’s spirit and normal life after surgery. Understanding and support from family and friends, professional services from psychiatrists, and proper guidance from medical staff are all beneficial to alleviate the shadow of embarrassment and low self-esteem brought by the stoma. On top of this, mutual support meetings and timely communication among patients will also relieve patients’ mental stress and negative emotions. Finally, proper guidance of patients’ post-operative habits is also an important part of their physical and mental recovery. This includes: smoking cessation, weight control, moderate exercise, change in diet structure (reduce the intake of red meat and processed meat, increase the intake of vegetables, fruits, fish and white meat), etc. Follow-up of colorectal cancer Several large-scale clinical studies have shown that after radical surgery, 80% of recurrent metastases occur within 3 years after surgery, and 95% of recurrent metastases occur within 5 years after surgery. Therefore, regular standardized postoperative follow-up can help to detect recurrent metastatic lesions in a timely manner and provide the possibility of reoperation for radical treatment or long-term survival with tumor. Currently, according to the NCCN guidelines, patients with postoperative stage I colorectal cancer should be reviewed by colonoscopy at 1 and 3 years postoperatively, and then every 5 years. Patients with stage II and III colorectal cancer should usually undergo chest CT and abdominopelvic enhanced CT or MRI and CEA at 4-6 weeks postoperatively, followed by repeat examinations every 3-6 months for 2 years postoperatively. These examinations can be completed every 6 months from the 3rd to the 5th year after surgery, and should be repeated every year after the 5th year. The frequency of colonoscopy can be referred to the follow-up requirements for stage I patients. However, special attention should be paid to the fact that if a patient has not completed a complete colonoscopy before surgery due to intestinal obstruction or other reasons, a colonoscopy should be performed about 6 months after surgery if there are no special circumstances. In addition, according to the available evidence-based medical evidence, PET-CT is not yet supported as a routine postoperative periodic imaging examination. However, PET-CT may be considered to look for recurrent metastases if the patient’s postoperative reexamination CEA level continues to be progressively elevated and there are no positive findings on enhanced CT and/or MRI. Or when recurrent or metastatic lesions are present and it is necessary to help determine whether the lesions are isolated and whether reoperation for radical treatment is possible, PET-CT may be considered to help with the overall condition.