Staying minimally invasive: robotic versus laparoscopic colorectal cancer surgery in a propensity-weighted Italian multicentre cohort.

To compare conversion to open surgery after intended robotic versus laparoscopic colorectal cancer resection in routine multicentre practice. This secondary post hoc analysis of the retrospective ATOCCS cohort included elective, curative-intent resections performed during 2022-2024 at Italian centres using both approaches. Propensity-score overlap weighting with centre indicators and multiple imputation addressed measured confounding and missing covariates. Centre-clustered models estimated adjusted risks, risk differences, and risk ratios. The primary cohort comprised 2,284 patients at 23 centres (1,408 laparoscopic; 876 robotic); conversion was evaluable in 2,278. Conversion occurred in 108/1,403 (7.7%) laparoscopic and 16/875 (1.8%) robotic procedures. Adjusted risks were 9.2% and 2.2%, respectively (risk difference, - 7.0 percentage points; 95% CI, - 11.1 to - 2.8; risk ratio, 0.24; 95% CI, 0.09-0.65; P=0.001). Within-centre propensity-score matching produced a similar risk difference (- 7.6 percentage points; 95% CI, - 11.3 to - 4.0). Major morbidity and reoperation did not differ detectably. Robotic surgery was associated with 42.8 min longer adjusted operative time (95% CI, 18.5-67.0), while the length-of-stay ratio was 0.91 (95% CI, 0.82-1.01). In dual-approach centres, intended robotic surgery was associated with fewer conversions but longer operations and no demonstrated improvement in the principal postoperative outcomes. Residual confounding precludes causal or superiority claims. Trial registration: ClinicalTrials.gov NCT07718919.