Oncological and anorectal functional outcomes of robot-assisted intersphincteric resection in lower rectal cancer, particularly the extent of sphincter resection and sphincter saving

Background Few investigations to date assessing the effectiveness of robot-assisted intersphincteric resection (ISR) have included sufficient patients and follow-up period. This study assessed the utility and safety of robot-assisted ISR by comparing groups of patients who underwent low anterior resection (LAR) with or without ISR and ISR extent. Methods This study enrolled 897 patients who underwent curative LAR between 2010 and 2017. Patients were divided into those who did (ISR+) and did not (ISR-) undergo ISR, with the former group subdivided by ISR extent (partial, subtotal, and total). Tumor recurrence and survival were compared in the two groups by one-to-one nearest neighbor matching (218 patients each). Results Robot-assisted ISR was performed via an entirely transabdominal approach in 93% of patients who underwent LAR. The rate of circumferential margin positivity was <= 2% in all patients and did not differ in the ISR- and ISR+ groups or in the three ISR+ subgroups. Mean fecal incontinence score and manometric values deteriorated significantly during postoperative until 12-24 months (p < 0.05 to < 0.001), but recovered subsequently. The 5-year cumulative rates of local recurrence in the ISR+ and ISR- groups were 2.5% and 2.9%, respectively (p = 0.731). The 5-year cumulative rates of overall (86.7% vs. 84.2%, p = 0.899) and disease-free (80.7% vs. 78.5%, p = 0.934) survival did not differ significantly in the ISR+ and ISR- groups. Conclusions Because ISR involves resection of low-lying tumors and complex pelvic dissection, robot-assisted ISR via a mostly transabdominal procedure may be technically more efficient, providing lasting anorectal function and good oncologic outcomes.