Causes of Open Conversion in Colorectal Cancer Surgery and Impact on Prognosis.

[PURPOSE] To examine the risk factors for open conversion during minimally invasive colorectal surgery and to investigate the impact of open conversion on short- and long-term prognosis.

[METHODS] Between 2016 and 2023, we retrospectively reviewed 4943 patients who underwent robotic or laparoscopic colorectal surgery. Patients were divided into those who underwent intraoperative open conversion (conversion group, n = 30) and those who underwent surgery without conversion (nonconversion group, n = 4913). Clinical characteristics were compared between the groups.

[RESULTS] Multivariate analysis revealed surgery performed by an expert surgeon (odds ratio [OR]: 0.361, 95% confidence interval [CI]: 0.158-0.822, p = 0.015) as a negative predictor and combined resection of adjacent structures (OR: 4.264, 95% CI: 1.715-10.604, p = 0.001), and clinical T4 disease (OR: 3.215, 95% CI: 1.415-7.465, p = 0.005) as positive predictors of open conversion. Open conversion was an independent predictor of postoperative complications (OR: 2.550, 95% CI: 1.201-5.414, p = 0.014) and relapse-free survival (hazard ratio [HR]: 3.343, 95% CI: 1.232-8.923, p = 0.030).

[CONCLUSION] Open conversions were less frequent when performed by experts and more common in advanced tumor stages. For patients at increased risk of conversion, the procedure should preferably be performed in centers with established techniques and experienced surgeons.