Robotic vs Laparoscopic and Open Surgery for Abdominopelvic Cancers

Study Design This was a single-center, retrospective cohort study conducted at Asan Medical Center, a large tertiary referral center in Seoul, Republic of Korea. The study protocol was approved by the Institutional Review Board of Asan Medical Center (approval number 2026-0316), and the requirement for written informed consent was waived due to the retrospective design. The study is reported in accordance with the Strengthening the Reporting of Cohort, Cross-sectional and Case-control Studies in Surgery (STROCSS) guideline.

Study Population Adults aged 18 years or older who underwent curative-intent abdominopelvic surgery for one of seven nonmetastatic malignant solid tumors (pancreatic, gastric, rectal, cervical, endometrial, kidney, or prostate cancer) between January 1, 2012, and December 31, 2021 were considered eligible. Patients were excluded if they had distant metastasis before surgery, presented with recurrent disease from previously treated cancer, or had incomplete key demographic, comorbidity, operative, or outcome data.

Exposure Patients were classified into three groups according to the surgical approach: open surgery, laparoscopic surgery, and robotic surgery. Two pairwise cohorts were constructed for comparative effectiveness analyses: (1) open versus robotic surgery for all seven cancer types, and (2) laparoscopic versus robotic surgery for six cancer types (prostate cancer excluded due to absence of laparoscopic prostatectomy at the study institution during the study period).

Primary Outcome

1-year disease-free survival (DFS), defined as the interval from surgery to the first occurrence of cancer recurrence, distant metastasis, or death from any cause. The 1-year time horizon was selected because postoperative oncologic surveillance was systematically available during the first postoperative year across the included malignancies.

Secondary Outcomes

• 1-year all-cause mortality
• Overall mortality during the entire follow-up period
• Major postoperative complications within 30 days (composite of cardiovascular events, stroke, venous thromboembolism, pneumonia, wound dehiscence, systemic infection, sepsis, acute kidney injury, and urinary tract infection)
• Postoperative acute kidney injury (KDIGO criteria)
• Hospital length of stay

Statistical Analysis Propensity scores were estimated separately for each pairwise comparison within each cancer type using multivariable logistic regression, incorporating demographics, tumor stage, surgical factors, comorbidities, preoperative medications, and laboratory measurements. Overlap weights were applied to emphasize patients with substantial covariate overlap without trimming. Time-to-event outcomes were analyzed using weighted Cox proportional hazards models with robust variance estimation. Pooled estimates across cancer types were obtained from models stratified by cancer type, with heterogeneity assessed by interaction testing. Binary outcomes were analyzed using Firth penalized logistic regression, and length of stay using weighted linear regression after log transformation. E-values were computed to assess sensitivity to unmeasured confounding.

Sensitivity Analyses A stepwise doubly robust strategy was applied. Model 1 was the primary overlap-weighted analysis. Model 2 additionally adjusted for surgical complexity (European Society of Cardiology surgical risk category and cancer-specific operation subtypes) and provider-level factors including cumulative robotic experience of the operating surgeon as a proxy for the robotic learning curve. Model 3 further adjusted for pathological severity (advanced T stage, nodal involvement, and FIGO stage where applicable) among patients with available staging.