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

Abstract

Background: Concerns persist regarding the effectiveness of robotic proctectomy when compared with open proctectomy for locally advanced rectal cancer with a high risk of circumferential resection margin involvement.

Objective: Comparison of surrogate cancer outcomes following robotic versus open proctectomy in this subpopulation.

Design: Retrospective cohort study.

Setting: Three academic hospitals (Mayo Clinic Arizona, Florida, and Rochester) through the Mayo Data Explorer platform.

Patients: Patients at high risk of circumferential resection margin involvement were selected based on the magnetic resonance imaging-based definition from Mercury I and II trials.

Primary and secondary outcome measures: Rate of pathologic circumferential resection margin involvement (≤1 mm), mesorectal grading, rate of distal margin involvement.

Results: Out of 413 patients, 125 (30%) underwent open and 288 (70%) 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 on 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% RP patients vs. 11.8% OP patients, p = 0.327). All cases had negative distal resection margins.

Limitation: Retrospective design.

Conclusion: 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. See Video Abstract.