In the second half of the 20th century, local resection of rectal cancer has the advantages of less surgical trauma, faster postoperative recovery, lower complication and death rate, avoidance of permanent colostomy, normalization of bladder function and sexual function, and similarity of postoperative physiological activities to those of normal people. The advantages of local resection for rectal cancer, such as less invasive surgery, faster postoperative recovery, lower complications and death, avoidance of permanent colostomy, normal bladder function and sexual function, and similar physiological activities to normal people after surgery, attracted attention. If the case selection is appropriate, the long-term outcome is not significantly different from that of transabdominal and transabdominal perineal radical resection. It should be noted that local excision of rectal cancer refers to complete removal of tumor and surrounding normal tissues, not palliative surgery, which is of great significance in preserving the function of anal sphincter and avoiding overtreatment on the premise of ensuring radical treatment. 1. Indications for local excision of rectal cancer: strictly mastering the indications for surgery and carefully selecting suitable cases are the keys to successful local excision of rectal cancer, on the basis of which the purpose of reducing surgical trauma, improving life quality and ensuring long-term curative effect can be achieved. At present, most scholars believe that the following conditions should be considered for case selection: (1) low to middle-grade rectal cancer, tumor diameter ≤3 cm, invading 40% of the circumference of the intestinal wall; (2) good tumor activity on rectal finger diagnosis, no basal infiltration, and the general type of tumor is augmentation, polyp or superficial ulcer; (3) lesions limited to the mucosa or submucosa (Tis/T1), for lesions invading the muscular layer (T2) (4) good histological type, high- or moderately differentiated adenocarcinoma or choriocarcinoma malignant, no lymph node metastasis or distant metastasis, no lymphovascular or vascular invasion. In addition, local excision is a good method that is safe and can preserve the anus for certain patients who are too old, poor in health, with vital organs (heart, lung, liver and kidney, etc.) that cannot tolerate transabdominal surgery or patients who refuse to undergo Miles. However, local resection should be abandoned in favor of conventional radical resection when the patient has (1) hypofractionated adenocarcinoma, (2) mucinous adenocarcinoma or indolent cell carcinoma, (3) intraoperative confirmation of tumor penetration through the muscularis propria (T3), (4) intraoperative confirmation of vascular invasion, and (5) intraoperative confirmation of local lymph node metastasis. Gopaul et al [5] retrospectively studied 64 cases of local resection of low rectal cancer with a mean follow-up of 37 (9-125) months, 15 cases of local recurrence, and a mean time to recurrence of 12 months. The local recurrence rate was closely related to the depth of infiltration, including 13% for T1, 24% for T2 and 71% for T3 recurrence. The worse the histological differentiation, the higher the recurrence rate (12% for highly differentiated, 24% for moderately differentiated, and 44% for poorly differentiated). The recurrence rate was as high as 50% in margin-positive patients, which was significantly higher than 16% in margin-negative patients. The recurrence rate after local resection was 16% for tumors ≤3 cm in diameter, which was significantly lower than that of 47% for those >3 cm. The local recurrence rate was 9% (1/11) in T2 patients treated with adjuvant radiotherapy and up to 36% (5/14) in those without radiotherapy. 3 of 4 T3 patients treated with adjuvant radiotherapy had local recurrence and 2 of 3 without radiotherapy had recurrence. The study concluded that local resection is an alternative treatment for well-differentiated rectal cancer with tumor diameter ≤3 cm and T1. T2 patients should be treated with postoperative adjuvant radiotherapy, and T3 patients with high recurrence rate after local resection should undergo radical resection with or without radiotherapy. Most scholars now believe that potential lymph node metastasis and residual cancer at the incision margin are important causes of recurrence after local resection. In the literature, the depth of infiltration and the degree of tumor differentiation are closely related to lymph node metastasis in rectal cancer, and the rates of lymph node metastasis in T0, T1 and T2 are 1.8%, 6.3% and 19%, respectively; the rate of lymph node metastasis in G1 tumors is 1.8%, which is significantly lower than that in G2 tumors, which is 24.1%. In China, Zhou et al. retrospectively studied the clinical data of 32 cases of low rectal cancer treated by local resection. The local recurrence rate of T1 patients was 17.9% (5/28), which was significantly lower than that of T2 patients (25% (1/4); the local recurrence rate of highly differentiated adenocarcinoma was 12.5% (3/24), which was significantly lower than that of moderately differentiated adenocarcinoma (37.5% (3/8). Borschitz et al. reported that the local recurrence rate after local R0 resection for low-risk T2 rectal cancer was as high as 29%. Zhao et al. concluded that patients with T2 rectal cancer should undergo radical resection because the former can obtain a higher survival rate than local resection. 2. Early diagnosis of rectal cancer: Pre-operative examination such as endoluminal ultrasound endoscopy (EUS), CT, MRI, and rectal diagnosis should be jointly applied to make more objective and accurate preoperative staging of tumor (Clinical Stage), and selection of suitable patients for local resection is the key to ensure the efficacy. Lin et al. reported that the accuracy of EUS in detecting the depth of infiltration of rectal cancer was as high as 86.7%, and Landmann et al. reported that the accuracy of EUS in detecting lymph node metastasis of rectal cancer was 70%, the false positive rate was 16%, and the false negative rate was 14%. In addition, CT and MRI examinations have been reported in the literature to further improve the accuracy of rectal cancer staging. The combination of rectal diagnosis and endoscopic morphology is also of great value in the diagnosis of early rectal cancer. If the tumor is still soft and can be pushed up and down, it can be judged as intra-mucosal cancer or sub-mucosal cancer. As for the distinction between the two, the morphology and size of the tumor should be taken into consideration. Those with bulging tissues and a diameter of about 1 cm are mostly intra-mucosal carcinoma; those with wider or inconspicuous tissues and a diameter of 1.5-3 cm are mostly sub-mucosal carcinoma. In addition, the clinical finger staging advocated by York Mason to determine the depth of lesion infiltration is also of considerable practical value, and the compliance rate with postoperative pathology is 80%, i.e. I: freely moving, mucosal or submucosal carcinoma; II: well moving, lesion invading the muscular layer; III: poorly moving, lesion involving outside the intestinal wall; IV: fixed, inactive, lesion involving the pelvic wall. Folkesson recently reported that local resection was performed in 643 (6.3%) of 10,181 cases of rectal cancer in Switzerland between 1995 and 2005, and the efficacy of local resection for early-stage rectal cancer was the same as that of transabdominal resection. Among them, the 5-year survival rate after local resection for 256 cases of stage I rectal cancer was 95.3% (confidence interval: 91.5-99.1%), and the local recurrence rate was 7.2%. 3.Surgical methods for local excision of rectal cancer: the surgical methods for local excision of rectal cancer mainly include: transanal excision (Parks), transoccygeal excision (Kraske), transsphincteric excision (Mason), and local excision of rectal cancer. excision (i.e. Mason’s operation) and transanal endoscopic microsurgery (i.e. TEM operation). The specific surgical approach and surgical methods should be selected reasonably according to the distance of the tumor from the anal verge and the operator’s familiarity with certain surgical methods, so as to ensure the radicality of local excision, improve the 5-year survival rate, reduce recurrence, and preserve the normal defecation, urination and sexual function, and improve the quality of life. For tumors >7cm from the anal verge, transabdominal resection is preferred; for tumors 5-7cm from the anal verge, trans-sacrococcygeal resection is preferred; for tumors less than 5cm from the anal verge, transanal or trans-sphincter resection is adapted. 3.1 Transanal resection: general anesthesia or sacral anesthesia is chosen for the operation. Depending on the location of the tumor, choose the position, with the tumor located in the anterior wall in the juck-knife position and the tumor located in the posterior wall in the lithotomy position. The anus is fully dilated to 5~6 fingers and maintained for 5 min until the anal sphincter is completely relaxed. The anal canal was retracted through the anoscope or spreader to fully reveal the tumor. The tumor was injected with 1/200,000 epinephrine saline into the submucosa and surrounding area at the base of the tumor, and then traction sutures were made at 1.5~2 cm from the upper, lower, left and right sides of the tumor, and the whole disc was excised with an electric knife at 1 cm from the edge of the tumor (for polyp malignancy, only the muscle layer could be cut). The tumor was completely excised, and the whole layer was sutured continuously with 3.0 vicryl absorbable sutures. The excised specimens were sent for rapid freezing examination to clarify whether the tumor was completely excised. Finally, the wound was checked for active bleeding, and if there was no abnormality, oil gauze was inserted into the anus to stop the bleeding and the operation was finished. Stamos et al. reported that transanal resection of T1 rectal cancer patients increased from 26% in 1989 to 44% in 2003. Several retrospective studies have shown recurrence rates as high as 18% and 47% after local resection for T1 and T2 rectal cancer, while a few prospective studies have shown recurrence rates of 4-5% and 14-16% after local resection for T1 and T2 rectal cancer, respectively. The reason for this may be related to the strict selection of patients enrolled in the prospective studies, and Fenech et al. reported a significant improvement in quality of life after transanal local excision in patients with early-stage rectal cancer. The median number of lymph nodes cleared by EPMR was 7 (1-22), which is slightly lower than the 11 lymph nodes cleared by EPMR. The median number of lymph nodes cleared by EPMR was 7 (1~22), which was slightly lower than that of 11 (2~36) by transabdominal low anterior resection, but the difference was not statistically significant (P=0.132). The study concluded that EPMR after transanal local resection is a safe and effective treatment for T1 rectal cancer, and has the advantages of lower postoperative complications and morbidity than transabdominal low anterior resection, and can reduce the local recurrence rate after transanal local resection alone. 3.2 Transsacrococcygeal resection: subarachnoid anesthesia or sacral canal anesthesia was chosen for the operation. The incision is made in the middle of the sacrococcygeal area, from the sacrococcygeal joint upwards to the top of the external anal sphincter, and the subcutaneous fatty tissue of the skin is cut and part of the gluteus maximus muscle is severed. If the tumor is close to the peritoneal fold, the caudal bone often needs to be removed to achieve full exposure. If the tumor is close to the anus, the anal levator muscle and puborectalis muscle need to be cut. In order to have adequate tumor margins, the rectum must be adequately freed up and down. The rectum is separated between the anterior sacral fascia and Waldeyer’s fascia to the level of the retroperitoneum, and the posterior wall of the rectum is adequately freed. The rectum is separated bluntly to the right and left to reach Denonvilliere’s fascia, and the anterior rectal wall is fully freed. If necessary, the anterior superior peritoneum can be opened to free the rectum from above and downward to reconstruct the Douglos fossa. If the tumor is located in the anterior wall, the posterior wall of the rectum is incised to reveal the lesion. Total resection includes the tumor and 1 cm of surrounding normal tissue. The rectal incision is closed with interrupted transverse sutures. The “mouth gas test” is performed to check for air leakage and repair accordingly. The anal levator and puborectalis muscles were carefully sutured, drainage was routinely placed, and subcutaneous tissue and skin were sutured. In China, Fu Tao et al. reported [20] that 12 cases of early rectal cancer were resected locally via the sacrococcygeal region, with an average hospital stay of 14.2 d. Two cases had incisional infections after surgery, which healed after drug changes, and none of them had urinary retention or sexual dysfunction. The mean follow-up time was 38 (2~110) m. Local recurrence occurred in 2 cases (16.7%) at the 7th and 14th postoperative months, respectively, with the former undergoing Miles surgery again. The study concluded that transsacrococcygeal local excision is an alternative safe and effective treatment for early rectal cancer of low malignancy. 3.3 Trans-sphincteric resection: general anesthesia was chosen for the procedure, with prone position. The incision is about 12 cm long, starting 3~4 cm above the sacrococcygeal joint and going down to the anal verge. The skin and subcutaneous tissues were cut, the anorectal ligament was cut by electric knife, and the sacrococcygeal joint was interrupted to remove the tail bone. The external anal sphincter, anal levator and puborectalis muscles were cut in groups and marked. The rectum was fully freed, and the posterior wall of the rectum was incised from the anal margin upward, and the lesion was exposed by a large papillary retractor to prop up the incision. According to the tumor site, size and circumference of the invasive bowel wall, local total rectal wall resection or rectal segmental resection or recto-rectal end-to-end anastomosis was performed. The Mason procedure has the following advantages: the surgical route is superficial and straightforward, with a spacious field and clear exposure; the surgical indications are wide, and most patients with lower and middle rectal cancer can be locally resected by this procedure; and sufficient resection area is ensured to reduce local recurrence after surgery. The disadvantage of this surgery is that the external anal sphincter must be severed during surgery, and postoperative anal incontinence is likely to occur. However, Qiu Huizhong et al [21] reported that this complication rarely occurred because the groups of external anal sphincters were correctly cut and anatomically repaired during surgery to avoid postoperative incisional infection. In this study, 30 cases of lower and middle rectal cancer (Tis5, T113, T210, and T32) were treated with Mason surgery, with a mean follow-up time of 52 (4-108) m, a 5-year survival rate of 93%, no local recurrence, normal postoperative defecation and control function, and no anal incontinence detected. The study concluded that the Mason procedure should be used as the procedure of choice for local excision of lower and middle rectal cancer. 3.4 Transanal endoscopic microdissection: TEM surgery was first pioneered by German surgeon Buess as a safe and effective minimally invasive treatment for benign rectal tumors and early rectal cancer. Patient preparation is the same as for transanal resection. The technique uses a specially designed 40mm diameter, 25cm long endoscopic instrument that can remove benign rectal tumors and early rectal cancers up to 10cm (anterior wall tumors), 15cm (lateral wall tumors) and 20cm (posterior wall tumors) from the anus. It has the advantage of being able to reach distances that cannot be reached by transanal resection, while providing a higher level of safety than open surgery; magnification of the operative field, which facilitates accurate resection of the tumor; short hospital stay, and low complication and mortality rates of less than 20% and 1.3% respectively. The main complications are bleeding and perforation. the disadvantages of TEM surgery are the expensive equipment, the steep learning curve, and the inability to remove draining lymph nodes for pathological staging. lin et al. reported 15 cases of rectal intraepithelial neoplasia and early rectal cancer undergoing TEM surgery, with an average operative time of 57 (40-90) min, bleeding volume of 35 (10-60) ml, and hospital stay of 4.5 (2-9) d. Kreissler et al. Kreissler et al. found that the incidence of bleeding and other complications after TEM surgery was significantly higher for masses on the lateral wall of the rectum, >2 cm in diameter and >8 cm from the anal verge. lozoche et al. retrospectively studied the clinical data of 135 TEM surgeries, of which T024 (17.8%), T166 (48.8%) and T245 (33.4%) were performed. 33.4%); the median follow-up time was 78 (36-125) m. The tumor-free survival rates of T1 and T2 rectal cancer patients were 100% and 93%, respectively, which were consistent with the efficacy of conventional surgery. There were 4 cases of local recurrence and 2 cases of distant metastasis after surgery, all in T2 patients. 52 TEM procedures were reported by Bretagnol et al, including T131, T217 and T34 cases, and 7 (13%) additional remedial procedures. The median follow-up time was 34 (1-102) m, and postoperative local recurrence occurred in 8 cases (15%). 4. Precautions for local resection of rectal cancer: adequate preoperative bowel preparation, preventive use of antibiotics, nutritional support as well as careful intraoperative hemostasis and reliable suture treatment are important means to avoid postoperative complications such as incisional infection, dehiscence, bleeding or intestinal fistula. Female patients should have vaginal douching 2 d before surgery, and intraoperative disinfection should be performed vaginally, which is especially important for anterior rectal wall tumors. Intraoperative importance is attached to the concept of tumor-free, and the surgical area can be flushed with iodophor followed by 0.5g of 5-Fu to prevent implantation metastasis and recurrence. Before removing the tumor, 1/200,000 epinephrine saline should be injected into the submucosa of the tumor base to separate the tumor from the basal tissue for easy removal and to reduce intraoperative bleeding. The posterior rectal wall should be separated between the anterior sacral fascia and Waldeyer’s fascia to avoid damaging the anterior sacral vein from causing hemorrhage during surgery. Tumor removal from the anterior wall should avoid damage to the posterior vaginal wall as well as the seminal vesicle gland and prostate gland, which may cause rectovaginal fistula and bleeding. After resection of tumor, pathological section is routinely sent for examination, and intraoperative frozen pathological examination is feasible if available, and it is required to judge the depth of tumor infiltration, circumferential margin and local lymph node metastasis to decide whether to perform additional remedial surgery. Postoperative follow-up should be closely followed up once every 3 months, including liver ultrasound, chest X-ray, rectal examination and proctoscopy, etc. Recurrence of rectal cancer after local resection may still be cured by remedial surgery.