Relationship between treatment modality and prognosis The prognosis of colorectal cancer is influenced by many factors, not only involving the biological characteristics of the tumor, but also related to the patient’s physical quality (physical and psychological quality) and other self conditions. However, the most important thing is still the comprehensive treatment measures mainly based on surgery. In terms of surgical quality, although there is no significant difference between manual suturing and anastomosis surgery in affecting prognosis, recent studies have proposed the surgeon as an independent factor in the prognosis of colorectal cancer. The degree of surgical standardization and proficiency of the surgeon directly affects the degree of cure and recurrence rate of surgery. This is particularly important in the surgical management of rectal cancer. mcArdle surveyed 13 Scottish consultant surgeons and the variation in 10-year survival rates of their surgical patients ranged between 20% and 63%. The German colorectal group (German colorectal cancer group) also reported significant differences in surgical outcomes for colon and rectal cancer. The reasons for this are not yet explained, but for rectal cancer the main reason seems to be the ability to adequately remove the local tumor based on the rectal mesenteric layer. To improve the cure rate and obtain the best prognosis for treatment, early detection, early diagnosis and treatment remain the key to improving survival. Precancerous lesions of the colorectum should not be ignored, and polyps or adenomas should be treated promptly according to clinical and pathological features. Comprehensive treatment, such as adjuvant radiotherapy, chemotherapy and immunotherapy, should be provided to preoperative and postoperative patients with the aim of improving the chance of radical cure by surgery or further eliminating local cancer foci or distant micrometastases after surgery to further improve the survival rate. Currently, preoperative radiotherapy is gaining more and more attention, but preoperative radiotherapy for colon cancer is not widely carried out. Among the many factors affecting prognosis, radiotherapy has a close relationship with the prognosis of rectal cancer. In the past, it was thought that rectal cancer was only mildly sensitive to radiotherapy, probably as a result of the fact that radiotherapy was mostly used in the past for patients who could not be surgically resected or had recurrence after surgery. With the development of radiotherapy technology, especially the research on the sensitizing effect of intracavitary contact radiation as well as chemotherapy and thermotherapy on radiotherapy, it has been confirmed that early, surgically resectable rectal cancer has better sensitivity to preoperative radiotherapy. It has been reported that in 25 patients with rectal cancer who were preoperatively irradiated with 40Gy/ 3 weeks photon beam and then underwent radical surgery, the survival rate and local recurrence rate of this group were significantly different than the control group. Their 5-year survival rate reached 60% to 70%, and the local recurrence rate was significantly lower. There was also a difference in the 5-year survival rate and local recurrence rate between surgery with and without radiotherapy [1] (Table 16-3-8). Postoperative radiotherapy is mainly used for T3 and T4 rectal cancers that have undergone radical surgery; patients with pathologically confirmed lymph node metastases; and patients with residual lesions or recurrence after surgery. For rectal cancer that can be resected surgically, postoperative radiotherapy can play a role in reducing pelvic recurrence, and it is controversial whether it can improve the postoperative survival rate. Postoperative radiotherapy is an effective comprehensive treatment for patients with recurrence of rectal cancer. Postoperative radiotherapy can shrink lesions, rapidly relieve pain and improve survival quality. Domestic studies have reported that complete remission (CR) can be achieved with stereotactic radiotherapy, heat therapy and chemotherapy, and there are even long-term survivors. At present, most of the adjuvant treatment for colorectal cancer is postoperative systemic chemotherapy, except for preoperative radiotherapy and chemotherapy for rectal cancer, and very rarely preoperative chemotherapy is administered because colorectal cancer is a tumor with relatively poor sensitivity to chemotherapy, and the effect of chemotherapy is not satisfactory. The efficiency of a single drug rarely exceeds 20%. Also, preoperative chemotherapy may cause toxic side effects and delay the timing of surgery. However, postoperative adjuvant chemotherapy for colorectal cancer as part of a combination therapy can improve survival by 15% to 30%, especially for patients with Dukes B or C stage. Recently, a combination regimen based on 5-fluorouracil (5-FU) has been affirmed. 5-FU plus aldehyde folic acid (Leucovorin, CF) has been established as the standard postoperative adjuvant treatment regimen for patients with Dukes B2 and C stage. After surgery for Dukes B or C stage rectal cancer, the postoperative local recurrence rate ranges from 15% to 60%, and if the tumor has invaded the intestinal wall or nearby tissues and has lymph node metastasis, postoperative adjuvant radiotherapy or radiotherapy is often used to reduce the local recurrence rate, for this reason, adjuvant radiotherapy and chemotherapy after radical rectal cancer surgery has become the standard treatment mode for stage II and III rectal cancer. Lindblad (1988) reported that the survival rate of the postoperative radiotherapy group was significantly higher than that of the surgical group, 54% and 27%, respectively.