Comparative Outcomes of Robotic Versus Open Proctectomy for Rectal Cancer at High Risk of Positive Circumferential Resection Margin

BACKGROUND: Concerns persist regarding the effectiveness of robotic proctectomy compared with open proctectomy for locally advanced rectal cancer with a high risk of circumferential resection margin involvement. OBJECTIVE: Comparison of surrogate cancer outcomes after robotic versus open proctectomy in this subpopulation. DESIGN: Retrospective cohort study. SETTING: Three academic hospitals (Mayo Clinic Arizona, Florida, and Rochester) with data available through the Mayo Data Explorer platform. PATIENTS: Patients at high risk of circumferential resection margin involvement were selected on the basis of the MRI-based definition from the MERCURY I and II trials. MAIN OUTCOME MEASURES: Rate of pathologic circumferential resection margin involvement (<= 1 mm), mesorectal grading, and rate of distal margin involvement. RESULTS: Out of 413 patients, 125 (30%) underwent open and 288 (70%) underwent robotic proctectomy. Open proctectomy was significantly associated with a greater proportion of cT4 tumors (39.3% vs 24.8%, p = 0.021), multivisceral/concomitant resections (40.8% vs 18.4%, p < 0.001), and less frequent total neoadjuvant therapy use (17.1% vs 47.1%, p = 0.001). Robotic proctectomy was less commonly associated with pathologic circumferential resection margin involvement (7.3% vs 17.6%, p = 0.002), including after adjustment for cT stage, neoadjuvant therapy, and multivisceral resection (OR 0.326; 95% CI, 0.157-0.670, p = 0.002). Propensity score matching for 66 patients per group and related multivariable analysis no longer indicated any reduction of circumferential positive margin rate associated with robotic surgery (p = 0.86 and p = 0.18). Mesorectal grading was comparable (incomplete mesorectum in 6% robotic proctectomy patients vs 11.8% open proctectomy patients, p = 0.327). All cases had negative distal resection margins. LIMITATION: Retrospective design. CONCLUSIONS: In patients with locally advanced rectal cancer at high risk of circumferential resection margin involvement, robotic proctectomy is an effective approach and could be pursued when technically possible as an alternative to open proctectomy.