Trans-anal or trans-abdominal total mesorectal excision? A systematic review and meta-analysis of recent comparative studies on perioperative outcomes and pathological result

Background: Trans-anal total mesorectal resection (TaTME) is a novel approach for rectal cancer. However, the perioperative and pathological outcomes of this procedure remain controversial. Method: A systematic literature search was performed using PubMed, Embase, Wanfang (China) and the Cochrane Library databases without restriction to regions or languages. We included 17 trials comparing TaTME with Laparoscopic TME (LaTME) for meta-analysis (MA). Fixed and random-effect models were used to measure the pooled estimates. Results: A total of 17 trials including 1346 patients were eligible for this MA. Pooled perioperative data using TaTME was associated with a significant reduction in estimated blood loss (WMD: 41.40, CI: 76.83 to -5.97; p = 0.02), hospital stay (WMD: 1.27, CI: 2.32 to -0.23; p = 0.02), conversion (OR: 0.28 CI: 0.15-0.52; p < 0.0001), readmission rates (OR: 0.42, CI: 0.25-0.69; p = 0.0007) and overall postoperative complications (OR: 0.73, CI: 0.56-0.95; p = 0.02). TaTME did not compromise surgical duration (WMD: 11.61, CI: 26.62-3.41; p = 0.13) or enhance complications including anastomotic leakage, ileus, urinary dysfunction, wound infection and pelvic abscess. Concerning pathological outcomes, the TaTME group demonstrated longer circumferential resection margins (CRM) (WMD: 0.91, CI: 0.58-1.24; p < 0.00001) and reduced CRM involvement (OR: 0.47, CI: 0.29-0.75; p = 0.002), whilst the distal resection margin (DRM) quality of the mesorectum and harvested lymph node were comparable. Conclusion: TaTME achieves similar surgical outcomes to LaTME, with the added advantage of a safe CRMs, reduced blood loss, shorter hospital stay, lower conversion and readmission rates, and lower postoperative morbidity. Long-term oncological and functional data are now required to confirm these findings.