Conversion rate to open surgery during transanal total mesorectal excision (TaTME) for rectal cancer: a single-center experience

Minimally invasive techniques for rectal cancer have demonstrated considerable advantages in terms of faster recovery and less post-operative complications. However, due to the complex anatomy and a limited surgical field, conversion to open surgery is still sometimes required, with a negative impact on the short-and long-term outcomes. The purpose of this study was to analyse the conversion rate to open abdominal surgery during laparoscopic transanal total mesorectal excision (TaTME) procedures performed at a high-volume Italian referral center. All consecutive TaTME performed for mid-to-low rectal cancer between 2015 and 2023 were reviewed, independently if treated with a primary anastomosis (with/without a diverting ostomy) or an end stoma. All procedures were performed using a standardized approach by the same surgical team. Patients with benign diagnosis that underwent different-from rectal resection procedures and cases pre-operatively scheduled for open surgery were excluded. The primary outcome of interest was the rate of conversion, defined as an un-planned intraoperative switch to open surgery using a midline laparotomy. Secondary aims included the comparison of patients who had a longer vs shorter operative time. Out of 220 patients, 210 were selected. In 187 cases, a primary anastomosis was performed, while 23 patients received a terminal colostomy (1 in the converted group; 22 in the full MIS- TaTME group, 10.6%). A surgical approach modification occurred in two cases, with a conversion rate of 0.95%. Median operative time was 281 min. Reasons for conversions included intra-operative difficulties impairing the mini-invasive procedure without intra-operative complications in one case, and difficulties in the laparoscopic control of an intraoperative bleeding due to a splenic lesion in another patient. Male sex and a higher BMI were found to be statistically significantly associated to longer operative time (respectively: p = 0.001 and p = 0.0025). In a high-volume center, a standardized TaTME is associated to a low conversion rate to open abdominal surgery.