Initial Clinical Experience with Single-port Robotic Transanal Minimally Invasive Surgery for Rectal Cancer Running head: Single-port robotic transanal minimally invasive surgery for rectal cancer

Background: Transanal minimally invasive surgery (TAMIS) is widely used for rectal lesion excision, with robot-assisted TAMIS (R-TAMIS) improving surgical ergonomics. The introduction of the da Vinci Single-Port (SP) robot, designed for endoluminal surgery, has brought new possibilities. The primary objective of this study was to assess the technical feasibility and efficacy of SPR-TAMIS. The secondary objective was to analyze perioperative outcomes. Methods: : Between April 2021 and March 2023, we included 14 consecutive rectal cancer patients who underwent SPR-TAMIS. Patient data, surgical specifics, and clinical outcomes were collected to assess SPR-TAMIS safety and feasibility. Results: : The mean patient age was 69.0 years, and all cases underwent full-thickness excisions. The mean tumor diameter was 5.6 cm, positioned 9.8 cm proximally and 6.9 cm distally from the anal verge. Negative margins were achieved in 93% of cases, with one requiring further resection. The mean operative time was 156 minutes, and the median hospital stay was 5.7 days. No mortalities occurred, but two patients experienced minor delayed morbidity manifesting as wound dehiscence and enteritis (Clavien-Dindo grade I). No recurrences were observed during 15 month follow-up. Conclusions: : SPR-TAMIS emerges as a safe and feasible alternative for selected early rectal cancers, offering enhanced visualization and potential advantages for resecting larger or proximal lesions and suturing. Further research should explore expanding its surgical indications.