Transanal total mesorectal excision (taTME) for rectal cancer: beyond the learning curve

Background: Transanal total mesorectal excision (taTME) is a surgical approach for low rectal cancer with a learning curve estimated at 40–50 cases. The experience among taTME surgeons beyond their learning curve is limited. Methods: A retrospective analysis of all taTME cases performed for rectal cancer at two tertiary care hospitals from 2014 to 2019 was conducted. Transanal surgeons had previously performed > 50 taTME cases. Demographic, perioperative, and short-term outcomes were analyzed. Results: Among 54 taTME patients, 74.1% were male and 27.8% had a BMI ≥ 30. Tumors were stage I (8), II (13), III (29), and IV (4). Complex cases included 4 local recurrences, 4 prior liver resections, and 2 with prior prostate cancer. Thirty tumors were located ≤ 6 cm from the anal verge. On staging MRI, 12 had a positive predicted circumferential radial margin (+CRM), and 4 had internal anal sphincter involvement (+IAS). Forty-seven patients received neoadjuvant therapy. A 2-team approach was used in 51 patients with laparoscopic (83.3%) or robotic (16.7%) abdominal assistance with a 9.2% conversion rate. Low anterior resection with sphincter salvage was achieved in 87% with 8 patients requiring intersphincteric resection. Anastomoses were hand-sewn in 57.4% and all patients were diverted. Median LOS was 5 days with a 42.6% 30-day morbidity rate and 3 postoperative mortalities (ARDS, pulmonary embolism and pseudomembranous colitis). Complete and near complete TME grade was achieved in 94.4% with a 3.7% rate of +CRM. At a median follow-up of 28 months, local and distant recurrence rates were 3.9% and 17.6%, respectively, with no cancer-related mortality. Conclusion: Indications for taTME at experienced centers have expanded to include complex reoperative cases, local recurrences, metastatic cancer, and tumors with threatened CRM or IAS with evidence of post-treatment tumor regression. In the latter cases, taTME achieves good short-term outcomes and may facilitate R0 resection.