Do not give up treatment after colorectal cancer recurrence. Local recurrence after colorectal cancer resection, also known as locally recurrent colorectal cancer, is one of the main reasons for failure of surgical treatment and death of colorectal cancer patients. In recent years, with the advancement of colorectal cancer research, development of surgical techniques and accumulation of experience, a series of measures to control local recurrence have emerged, including total mesorectal excision (TME), total pelvic lymph node dissection, intraoperative tumor-free operation, intraoperative adjuvant radiotherapy and chemotherapy, and preoperative neoadjuvant chemotherapy. Even so, the recurrence rate of colorectal cancer after surgery is still high, the quality of life with tumor survival after recurrence is poor, and surgical re-treatment is difficult, and recurrent colorectal cancer has been a difficult problem for surgeons. I. Recurrence rate and factors affecting it The local recurrence rate of colorectal cancer after surgery varies from 5% to 50%. Why is there such a big difference in the postoperative recurrence rate of colorectal cancer patients reported by different countries? We believe that the main influencing factors are the length and quality of follow-up, the number of cases, the criteria for defining recurrence, the patient’s tumor stage, the surgical method, the adjuvant treatment and the operating level of the surgeon. The difficulty in unifying the influencing factors is an important reason for the large disparity in recurrence rates, and the lack of routine autopsy verification in most of the clinical studies, the local recurrence rate may be underestimated. There are many factors that influence local recurrence, and many of those known to influence survival also influence local recurrence. the worse the Dukes stage, the greater the likelihood of local recurrence. In a bulk case survey after abdominoperineal resection, the rate of local recurrence was 9.1% in Dukes stage A, 16.7% in stage B, and 40.8% in stage C. Similarly the extent of tumor infiltration outside the intestine also influenced recurrence, with higher local recurrence rates of 14.5% when the tumor was located in the lower 1/3 of the rectum, 8.3% when it was located in the middle 1/3 of the rectum, and a lower rate of 5.2% in the upper 1/3 of the rectum. Local recurrence after surgery in colon cancer patients is more common in the hepatic flexure, splenic flexure and transverse colon of the colon. In addition, patient’s age, tumor size, shape (mass type or infiltrative type), biological characteristics, differentiation degree, whether the tumor is fixed, whether there is infiltration of vasculature and nerves, whether there is obstruction perforation and whether there are tumor infiltrative lymphocytes are all important factors affecting the recurrence of tumor after surgery. The chance of local recurrence and metastasis is often seen in patients with relatively young age, hypofractionated adenocarcinoma and indolent cell carcinoma, and intraventricular thrombus in clinical practice. There is no doubt that surgeon’s experience and surgical skills directly affect the rate of local recurrence after surgery for colorectal cancer patients. Dr. Heald’s pioneering advocacy and application of TME technique in the anterior resection of low rectal cancer has reduced the rate of local recurrence after resection of low rectal cancer to 2.6%, which is a good example. Clinical manifestations and diagnosis of local recurrence About 65-80% of recurrences of colorectal cancer occur within 2 years after surgery, and only 6-8% of recurrences occur after 5 years. Since early recurrence symptoms may be quite insidious, regular follow-up review within 2-5 years is an important measure for early detection of recurrence foci. Any follow-up review should include history taking, colonoscopy, vaginal perineal examination, local ultrasound and tumor markers such as CEA. Sacrococcygeal pain, bloody stools, abdominal distension, and localized masses are common symptoms of local recurrence. When the recurrent tumor invades adjacent organs, corresponding symptoms will appear, such as hematuria, difficulty in urination, urinary urgency and frequency, vaginal bleeding when invading the vesicoureter and vagina; if invading the duodenum and pancreas, corresponding symptoms such as obstruction will appear. Imaging examinations such as in vitro and intracorporeal ultrasound, CT, MRI play an important role in diagnosing local recurrence of colorectal cancer after surgery, not only because they can directly obtain imaging evidence of local recurrence, but also because puncture biopsy is feasible under ultrasound and CT guidance to obtain pathological evidence. Currently, advanced equipment such as PET and PET/CT can detect local recurrence of tumors early and accurately. tumor markers such as CEA and CA19-9 can be used as indicators of early recurrence, and several studies have shown that an increase in CEA significantly precedes positive imaging findings. persistently elevated CEA may have recurrence in 58%-95% of asymptomatic patients. In addition, the form of CEA elevation also reflects the characteristics of recurrence. A slow increase in CEA is often indicative of local recurrence or limited metastasis, while a steep increase or stepwise increase often indicates disseminated lesions. Treatment of local recurrence (a) Surgical treatment of local recurrence For most patients with clinical symptoms of local recurrence, either radiotherapy or systemic chemotherapy is only palliative. If possible surgical resection is still curable for some cases, unfortunately only 5-20% of recurrence patients are resectable. Early diagnosis is important to improve the resection rate of local recurrences, especially in patients with asymptomatic recurrences, and Schiessl et al. reported that early detection resulted in resection of 49% of locally recurrent lesions, with the aim of re-curing them, and 30% survived for at least 35 months. In another study, the determination of CEA-guided surgery resulted in a complete resection rate of 60% and a 5-year survival rate of 30% for local recurrences. At this stage, the consensus is that aggressive reoperative intervention with extended salvage surgery can greatly improve the prognosis of patients with local recurrence after colorectal cancer surgery. However, due to the relatively high mortality and complications of this type of surgery, there are still different views on the timing and mode of surgical intervention for local recurrence after radical resection of colorectal cancer. Indications for recurrence surgery after colorectal cancer resection: ①Good general condition and nutritional status, no important organ insufficiency. ② Relatively limited recurrent tumor and no extensive metastasis in the abdominal cavity. ③No extra-hepatic distant metastases, such as lung, brain and bone metastases. ④ Relatively limited recurrent tumor in perineum and pelvis, no invasion of pelvic wall, no lower limb lymphedema and no sciatica. The ways to operate again for local recurrence of colorectal cancer after resection include: 1. Expanded local resection again For isolated non-anastomotic recurrent lesions, the lesions can be completely removed together with some surrounding normal tissues. For recurrent lesions located at the anastomosis, the anastomosis can be performed again under the premise of ensuring complete resection of recurrent lesions and safety of the incision margin. If this requirement is not met or if the recurrent tumor is fixed and invades the surrounding tissues, Miles surgery should be performed. Special attention should be paid to the fact that the normal anatomical structure has been changed during the second surgery, and care should be taken to protect the surrounding organs, such as ureter, vagina, duodenum and pancreas, while removing the lesion. The lymph node dissection during the secondary surgery should be implemented according to the specific intraoperative conditions and completed as much as possible under the premise of safety. If there is no extensive implantation metastasis or extrahepatic metastasis in the abdominal cavity, joint organ resection can be considered. Postoperative recurrence of colon cancer often invades ureter, kidney, liver, spleen, pancreas and duodenum, and if the patient’s condition allows, one, two or even three combined organ resections can be considered, which can still achieve the purpose of prolonging survival after surgery. For recurrent cases of rectal cancer, combined resection of pelvic organs, including bladder, rectum, uterus, vagina, prostate, urethra, and related adjacent tissues, can be considered if the surrounding organs are invaded. For recurrent rectal cancer lesions that invade surrounding structures and organs, pelvic organ resection or combined sacrocolpopexy is the only surgical option. In female patients, posterior pelvic organ resection is often performed because the uterus serves as a barrier and the bladder is relatively less likely to be involved. In male patients, the bladder, prostate, urethra, and ureter are often invaded, often requiring total pelvic organ resection. To ensure the safety of the lateral margins, the lateral lymph nodes must be cleared and the involved organ must be removed in its entirety, 2 cm from the edge of the tumor. Recurrent pelvic tumors located posteriorly are often closely related to the sacrum, and sacral resection is often required to ensure that there is no residual tumor at the incision margin. The 5-year survival rate of cases with combined pelvic organ resection can reach 20%-30%, while the 5-year survival rate of cases with palliative surgery only is 0, suggesting that pelvic organ resection can significantly improve the prognosis. 3.Sacral partial resection In cases of postoperative recurrence of rectal cancer, the tumor often invades the sacrum, and the purpose of radical cure cannot be achieved without joint resection of the affected sacrum. The scope of tumor invasion to sacrum can be clarified by CT and MRI examination before surgery, if it is below S2 level, it can be jointly resected, if it involves sacral spinal cord and invades above S2 level, it cannot be resected. Note that it is not necessary to free the tumor during the operation, and 2 cm away from the tumor and the affected sacrum can be removed together with the whole block. 4.Palliative surgery When the above surgery cannot be completed, palliative surgery should be paid attention to, which can achieve the purpose of partial symptom control and effectively improve the quality of patients’ survival with tumor. (2) Non-surgical treatment for local recurrence of colorectal cancer after resection Non-surgical treatment includes radiotherapy and chemotherapy. Radiotherapy can be divided into radical radiotherapy and palliative radiotherapy. If surgery has achieved the requirement of radical treatment, radiotherapy can be added after postoperative recovery to irradiate the tumor bed, which can reduce the chance of recurrence. Intraoperative radiotherapy or/and postoperative radiotherapy can also be adopted. Intraoperative radiotherapy can achieve direct and accurate irradiation of the tumor bed under direct vision and reduce the damage to the surrounding tissues and organs. If the chance of surgery has been lost or palliative surgery has been performed, radiotherapy can also be adopted to significantly reduce local symptoms, such as pain and bleeding, and to improve the quality of survival with tumor. It is well recognized that chemotherapy can reduce the recurrence rate of colorectal cancer patients, and it is still an effective treatment for recurrent colorectal cancer patients. Especially neoadjuvant chemotherapy, with the continuous improvement and updating of chemotherapy drugs and protocols, can shrink the originally unresectable lesions and create the time for surgical resection. Many new methods such as intraoperative implantation of slow-release chemotherapeutic drugs in the tumor bed and unresectable tumors and regional arterial infusion chemotherapy are increasingly applied to recurrent colorectal cancer cases and have also achieved certain results. After rectal cancer surgery, especially after radical abdominoperineal resection, the appearance of perineal mass is often a manifestation of local recurrence of tumor, accompanied by local sensation of falling, persistent distension and pain and dispersion to the lower limbs, and some may have hematuria, difficulty in urination, vaginal bleeding and edema of the lower limbs. Patients with anterior rectal resection may present with blood in the stool and difficulty in defecation. CT examination can clarify the diagnosis and indicate the extent of recurrent tumor and the involvement of surrounding organs. If necessary, puncture biopsy can be performed to clarify the diagnosis. Local recurrence of perineum after rectal cancer surgery is mostly found in cases of Dukes stage B and C. Low differentiation of tumor, intraoperative tumor penetration, reluctant ultra-low anastomosis and failure to follow the principle of TME are factors of recurrence. Postoperative perineal masses of rectal cancer are still treated with comprehensive treatment based on surgical resection. For patients who do not have extensive metastasis and can tolerate surgery, surgical resection should be pursued first, and neoadjuvant chemotherapy can also be taken before surgery in order to reduce the tumor and improve the efficacy. In cases of local recurrence after anterior rectal resection, for isolated non-anastomotic recurrent lesions, the lesions can be completely excised together with some surrounding normal tissues. For recurrent lesions located at the anastomosis, anastomosis can be performed again under the premise of complete resection of recurrent lesions and safety of the incision margin, and anal preservation surgery can be performed again. If the recurrent tumor is relatively isolated and does not invade the surrounding organs, and the location is not too high, we can consider enlargement of perineal resection, but there are more complications in this surgery, and the damage to urethra, bladder, vagina and small intestine may occur. If the location of the recurrent tumor is slightly higher than sacral 2 by CT examination before surgery, and the tumor does not invade the organs in front, and the patient cannot tolerate a larger operation, transsacral resection of the tumor can be considered, and if the tumor invades the sacrum below S2 backward, it can be removed together. If the tumor is in a higher position and the patient is in good general condition, transabdominal surgery can be performed, and if necessary, partial or total combined pelvic organ resection can be performed. Postoperative treatment is supplemented by chemotherapy and radiotherapy.