Omentectomy Versus Omental Preservation During Gastrectomy for Gastric Cancer: Systematic Review and Reconstructed Individual Patient Data Meta-Analysis

Background/Objectives: The oncological benefit of routine omentectomy (OmR) during curative gastrectomy for gastric cancer (GC) remains controversial. While omentectomy has traditionally been performed to reduce peritoneal dissemination, the greater omentum also possesses immunological functions that may protect against tumor implantation. This study evaluated the impact of OmR versus omental preservation (OmP) on long-term survival using reconstructed individual patient data (IPD) and restricted mean survival time difference (RMSTD) meta-analysis. Methods: A systematic review was conducted according to PRISMA 2020 guidelines. Comparative studies reporting Kaplan–Meier curves for overall survival (OS) and/or disease-free survival (DFS) after OmR versus OmP were included. IPD were reconstructed from published survival curves, and pooled RMSTD estimates were calculated using random-effects multivariate meta-analysis. Flexible hazard-based regression models assessed time-varying treatment effects. Secondary outcomes included postoperative morbidity and operative outcomes. Results: Fifteen studies involving 5325 patients were included, of whom 54% underwent OmR. At 60 months, no significant difference in OS was observed for OmR vs. OmP (−0.79 months, 95% CI −2.13 to 0.54). Similarly, DFS did not differ significantly (−2.12 months, 95% CI −4.59 to 0.35). Time-varying hazard analyses demonstrated no survival advantage for OmR throughout follow-up. OmR was associated with significantly higher intraoperative blood loss (MD 42.9), overall complications (RR 1.17), and longer hospital length of stay (MD 0.49). Retrieved lymph nodes, anastomotic leak, operative time, and 30-day mortality were comparable. Conclusions: In this study, routine omentectomy during gastrectomy for gastric cancer was not associated with improved OS or DFS compared with omental preservation. These findings question the need for routine omentectomy and suggest that omental preservation may represent a reasonable surgical strategy in selected patients, pending confirmation from prospective randomized trials.