Omentectomy as part of radical surgery for gastric cancer: results of a multicenter prospective cohort study

Abstract Background Omentectomy is routinely performed in patients with gastric cancer as part of sub(total) gastrectomy with modified D2 lymphadenectomy. However, there is little evidence for a survival benefit of omentectomy. This study investigated both the prevalence of metastases in the greater omentum and the survival prognosis for patients afflicted with such omental involvement. Methods This was a multicenter prospective cohort study (OMEGA study) of consecutive patients with gastric cancer undergoing (sub)total gastrectomy with complete en bloc omentectomy and modified D2 lymphadenectomy. After resection, the omentum was separated from the gastrectomy specimen distal to the gastroepiploic vessels and sent separately for pathological examination. The main endpoints were the presence of metastases in the greater omentum and the 5-year overall survival of patients with omental metastases. Pathological factors associated with locoregional recurrence and/or metastases were tested with multivariable regression analysis. Results Of 100 included patients, five had metastases in the greater omentum. All five patients had advanced tumors and microscopically non radical resection (R1). Metastases in the greater omentum correlated significantly with a microscopically non-radical resection, tumour expansion in the oesophagus or duodenum, linitis plastica or a proximal gastric tumour with diameter of at least 5 cm, stage III-IV disease and (y)pM1 category. Five-year overall survival was 0.0% in patients with omental metastases and 44.2% in patients without omental metastases (p=0.001). Median overall survival was seven months in patients with omental metastases and 53 months in patients without omental metastases. Conclusions The incidence of metastases in the greater omentum is low, and when present, it is associated with advanced and unresectable disease with impaired overall survival. Omentectomy as part of radical gastrectomy for gastric cancer may not contribute to survival benefit in cases of undetected omental metastases and may therefore be omitted. Our forthcoming randomized controlled trial aims to investigate the non-inferiority of omentum preservation as compared to omentectomy in terms of 3-year overall survival.