Transanal versus transabdominal total mesorectal excision for rectal cancer in minimally invasive surgery: meta-analysis

BACKGROUND: Colorectal cancer is a common malignancy. Despite advances in minimally invasive surgery, achieving optimal outcomes for locally advanced rectal cancer remains challenging. Transanal total mesorectal excision (TaTME) is an alternative to laparoscopic total mesorectal excision (LapTME), but inconsistent data warrant a comprehensive meta-analysis of the two procedures. METHODS: A systematic search was conducted across the PubMed, Embase, and Cochrane Library databases up to June 2025 using keywords related to rectal cancer and TaTME. The study protocol was registered with PROSPERO. Inclusion criteria followed the PICOS framework, selecting randomized clinical trials (RCTs) and observational studies comparing TaTME with LapTME or robotic total mesorectal excision (TME). Studies reporting on non-malignant cases, single-arm studies, and studies with insufficient data for analysis were excluded. Primary outcomes of interest were surgical metrics (operative time, conversion rates), pathological outcomes (circumferential resection margin (CRM), TME completion), oncological outcomes (local recurrence, overall survival), and functional outcomes (major low anterior resection syndrome (LARS)). RESULTS: In all, 65 studies involving 13 972 participants met the inclusion criteria. TaTME had lower conversion rates (odds ratio (OR) 0.35; 95% c.i. 0.24 to 0.51; P < 0.01), improved TME completeness (OR 1.26; 95% c.i. 1.02 to 1.55; P = 0.03), and lower CRM positivity (OR 0.7; 95% c.i. 0.58 to 0.85; P < 0.01) compared with LapTME. Local recurrence was reduced (OR 0.69; 95% c.i. 0.55 to 0.87; P < 0.01) and overall survival improved (hazard ratio 0.80; 95% c.i. 0.70 to 0.91; P < 0.01) following TaTME, but TaTME was associated with a higher risk of major LARS (OR 1.58; 95% c.i. 1.11 to 2.24; P = 0.01). Subgroup analysis revealed consistent results across RCTs and cohort studies. CONCLUSION: TaTME offers several advantages over LapTME, including lower conversion rates and improved CRM and oncological outcomes. The increased risk of major LARS with TaTME underscores the importance of balancing functional outcomes with other benefits. Future research should focus on optimizing functional recovery and addressing high heterogeneity across studies.