Objective To evaluate the clinical efficacy of transanal total mesorectal excision (taTME) on transanal endoscopic microsurgery (TEM) platform in the treatment of middle and low rectal cancer.

Methods The retrospective and descriptive study was conducted. The clinico-pathological data of 28 patients with middle and low rectal cancer who underwent taTME on TEM platform in the Peking Union Medical College Hospital of Chinese Academy of Medical Science from October 2014 to October 2017 were collected. There were 21 males and 7 females, aged 59 years (51 years, 68 years). Observation indicators: (1) surgical and postoperative situations; (2) follow-up. Follow-up was conducted using outpatient examination or telephone interview to detect post-operative defecation function and survival of patients up to October 2020. Patients underwent physical examination, examination of tumor markers including carcinoembryonic antigen and CA19-9, colonoscopy, rectal magnetic resonance imaging, thoracoabdominal and pelvic enhanced computed tomography (CT) and (or) PET-CT examination during the follow-up. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was analyzed using the independent sample t test. Measurement data with skewed distribution were represented as M(P25,P75) or M (range), and comparison between groups was analyzed using the non parameter Mann-Whitney U test. Count data were described as absolute numbers or percentages, and comparison between groups was analyzed using the chi-square test or Fisher exact probability.

Results (1) Surgical and postoperative situations: 28 patients underwent successful surgery, without intra-operative conversion to laparotomy. Of 28 patients, 24 cases underwent colorectal anastomosis and 4 cases underwent colon-anal anastomosis. Twenty-six cases underwent primary protective enterostomy and 2 cases didn't undergo primary protective enterostomy. The operation time of 28 patients was (182±37)minutes and the volume of intraoperative blood loss was 40mL(30 mL, 55 mL). One patient with intraoperative presacral hemorrhage received compression hemostasis. Eleven patients had postoperative complications, including 4 cases with anastomotic leakage, 2 cases with alteration of intestinal flora, 2 cases with paralytic ileus, 2 cases with urinary retention, 2 cases with urinary infection, 1 case with prolapse necrosis of small intestinal stoma, 1 case with anal hemorrhage, 1 case with rectovaginal fistula, 1 case with pelvic infection; some patients had multiple complications. Three patients had non-planned reoperation. One case without primary protective enterostomy had anastomotic leakage at postoperative 3 days, and was improved after emergency transversostomy. One case had prolapse necrosis of small intestinal stoma at postoperative 3 days and was improved after emergency enterostomy and reconstruction. One case with anal hemorrhage was stopped hemorrhage under anoscopy. Patients with other complications were cured after conservative treatments. The duration of postoperative hospital stay of 28 patients was 8 days(7 days, 9 days). Results of pathological examination in 28 patients showed 16 cases of moderately differentiated adenocarcinoma, 3 cases of moderately to highly differentiated adenocarcinoma, 5 cases of highly differentiated adenocarcinoma, 1 case of mucinous adenocarcinoma, 3 cases of pathological complete response. TNM staging of 28 patients showed 3 cases in stage T0N0, 4 cases in stage T1N0, 6 cases in stage T2N0, 4 cases in stage T2N1, 7 cases in stage T3N0, 3 cases in stage T3N1, 1 case in stage T4N1. The distance from tumor to distal margin was (2.2±1.7)cm. The surgical specimens of 28 patients showed negative for proximal, distal and circumferential margins. The number of lymph node dissection was 15±7. The complete rate of total mesorectal excision was 100%(28/28). Eleven of 28 patients underwent neoadjuvant therapy and 17 patients didn't receive neoadjuvant therapy. The tumor diameter, distance from tumor to anal margin, operation time, volume of intraoperative blood loss, duration of postoperative hospital stay were 2 cm(1 cm, 4 cm), 5 cm(4 cm, 6 cm), (187±25)minutes, 45 mL(38 mL, 53 mL), 8 days(7 days, 12 days) for patients with neoadjuvant therapy, respectively, versus 3 cm(2 cm, 4 cm), 5 cm(4 cm, 6 cm), (177±35)minutes, 40 mL(30 mL, 60 mL), 8 days(7 days, 8 days) for patients without neoadjuvant therapy, showing no significant difference between the two groups (Z=-1.127, -0.293, t=0.590, Z=-0.790, -0.876, P>0.05). (2) Follow-up: 23 of 28 patients were followed up for (44±14)months. Of the 23 patients,11 cases were classified as grade A of Williams score for defecation function at postoperative 6 months, 8 cases were classified as grade B and 4 cases were classified as grade C. Eighteen of 23 patients with follow-up had disease-free survival, 1 of whom didn't undergo stoma closure due to anastomotic stenosis at postoperative 6 months. Three patients had distant metastasis, including 1 case with parastomal implantation metastasis, 1 case with sacral metastasis, 1 case with pulmonary metastasis. Two patients died, 1 case of whom died of urinary obstruction and 1 case with mucinous adenocarcinoma died at postoperative 24 months.

Conclusion TaTME based on TEM platform is feasible for middle and low rectal cancer, which has the advantages of preserving anus and negative circumferential margin.