Evaluation of the learning curve of laparoscopic-assisted transanal total mesorectal excision for rectal cancer

[Objectives] To evaluate the learning curve of laparoscopic-assisted transanal total mesorectal excision (LA-taTME) for rectal cancer and provide reference for clinical practice of this procedure. [Methods] The clinical data of 118 patients with rectal cancer who underwent LA-taTME were retrospectively analyzed. The learning curve of operative time of LA-taTME was drawn by cumulative summation (CUSUM) method, and the minimum number of operation to cross this learning curve was analyzed. The learning curve of operative technique of LA-taTME was drawn by risk-adjusted cumulative summation (RA-CUSUM) method, and the minimum number of operation to master this operative technique was analyzed. Additionally, the clinical data was analyzed and the general information and perioperative data was compared between the group A (at the phase of learning and familiarizing with operative technique) and the group B (entered the proficient stage). We focused on the general information about age, gender, distribution of different body mass indices, distribution of different angles of levator ani muscle, maximum tumor diameter, distance from lower tumor margin to anal margin and tumor T stage, and perioperative data of operation time, intraoperative blood loss, number of lymph nodes harvested, incidence of anastomotic leakage, and postoperative complications of Clavien-Dindo grade Ⅰ-Ⅲ were collected. [Results] Eighty-four cases of operation was the minimum number to cross the learning curve of operative time of LA-taTME for rectal cancer by CUSUM method. Forty-two cases of operation was the minimum number to enter the proficient stage of operative technique of LA-taTME for rectal cancer by RA-CUSUM method. The patients were divided into the group A and the group B, with 42 cases and 76 cases, respectively. The age, distribution of different body mass indices, distribution of different angles of levator ani muscle, maximum tumor diameter, distance from lower tumor margin to anal margin and tumor T stage were comparable between the group A and the group B (P>0.05), while the pro-portion of men was lower in the group A, with a statistically significant difference (P<0.05). The operative time was longer and intraoperative blood loss was more in the group A, with a statistically significant difference (P<0.05), while the number of lymph nodes harvested and incidence of anastomotic leakage did not differ between the two groups (P>0.05). There were 7, 3, 4 cases of postoperative complications of Clavien-Dindo grade Ⅰ, Ⅱ, Ⅲ in the group A, with 7,3, 0 cases in the group B correspondingly. [Conclusion] Eighty-four cases of operation was the minimum number to cross the learning curve of operative time of LA-taTME for rectal cancer by CUSUM method. Forty-two cases of operation was the minimum number to enter the proficient stage of operative technique of LA-taTME for rectal cancer by RA-CUSUM method.