Omentectomy has never been shown to provide a survival benefit in gastric cancer patients [1,2,3,4,5,6,7,8]. Despite that, it is still recommended as the standard treatment for advanced gastric cancer [13]. Omentum preservation dramatically facilitates the operation and reduces intraoperative and postoperative complications in laparoscopy. Meanwhile, some concerns have been raised that omentum preservation could lead to more peritoneal recurrence in patients with advanced gastric cancer. In the present paper, we confirmed that omentum resection did not provide any survival benefit compared to laparoscopic gastrectomy with omentum preservation.

Our study showed no differences in the 5-year survivals between patients after laparoscopic omentum-preserving gastrectomy and open surgery with omentectomy. In the multivariate analysis, only the UICC stage and age were determined to have significantly impacted survival in our patient group, while the complete omentectomy did not have any significant impact on the overall survival. Similar results were obtained by other retrospective studies [3,4,5,6,7]. These studies are prone to selection bias due to their retrospective nature. We adjusted for the most significant factors influencing survival to avoid such a selection bias. Our patients were balanced in regard to UICC stage distribution, age, ASA grade, tumor location, type of operation, and were all operated on in the same period. An important factor to consider in patient selection is chemotherapy. Perioperative treatment is the standard for patients with stages Ib or higher in Europe [13]. The FLOT4 study demonstrated that patients receiving chemotherapy have a significant survival advantage [14]. In the study conducted by Hasegawa et al., there was a significant difference in the proportion of patients receiving adjuvant treatment, with patients in the omentum-preserving group receiving adjuvant treatment in a greater proportion [5]. This might have influenced the comparability of the results. To adjust for this factor in our study, perioperative treatment was used as a co-factor for PSM, making our patient groups well-balanced.

Omentectomy has the advantage of theoretically removing microscopic tumor seeds and preventing the spread of malignancy [5]. If omentectomy prevented peritoneal recurrence, we would expect significant differences in the modes of recurrence between LAP and OPN groups. Our study showed no difference in the recurrence sites between groups. Peritoneal recurrence was the most common type of recurrence in both groups, as reported by other authors [5,6,7]. The logistic regression model confirmed that only the UICC stage was significantly associated with peritoneal recurrence and that laparoscopic gastrectomy with omental preservation did not lead to a higher risk for peritoneal recurrence.

The patients in LAP group had lower morbidity rates compared to OPN group. Complete omentectomy has been shown to be related to a higher incidence of complications [3,4,5,6,7,8]. Our results support these findings. Omentum preservation facilitates the laparoscopic resection, shortens the time of the surgery, and produces less blood loss [1,2,3,4,5,6,7,8]. It also has an important anti-inflammatory role and can adhere to the site of potential leaks from the anastomosis [1,2,3,4,5,6,7,8]. Our morbidity rates compare favorably to recent RCTs where patients received a laparoscopic total gastrectomy in a similar proportion as in our study [15,16,17]. The mortality rates in both groups were 1% and comparable to previous reports on laparoscopic gastrectomies from Eastern RCTs [18,19,20,21,22]. An important late morbidity to consider is intestinal obstruction. Theoretically, the preserved omentum could cause intestinal adhesions and obstruction. Our results confirmed that omentum preservation did not lead to more intestinal obstructions. Finally, patients in the LAP group had significantly shorter hospital stays compared to OPN group. The JCOG0912 and KLASS01 trials have demonstrated superior postoperative recovery in terms of shorter hospital stays after laparoscopy compared to open surgery [18, 19]. This was also evident in the present study.

In our study, a D2 dissection was performed in 75% to 78% of cases. Meanwhile, patients in the LAP group had a significantly higher number of extracted lymph nodes per operation compared to OPN group. Thus, laparoscopy and omental preservation did not lead to an inferior quality of lymph node dissection. On the contrary, we feel that laparoscopy might be associated with a more precise lymph node dissection due to magnification and better anatomical exposure than open surgery. A similar result was published in a recent meta-analysis by Liao et al., where an insignificantly higher lymph node was obtained in laparoscopically operated patients [23].

This is the first Western study comparing the oncological feasibility of laparoscopic omentum-preserving gastrectomy compared to open surgery with omental resection. We could only find one study from a Western center with results of omentum-sparing laparoscopic surgery [24]. Therein, Olmi et al. presented their ten-year experience of laparoscopic omentum-preserving gastrectomy. Nevertheless, they did not compare omentum-preserving gastrectomy to omentum-resecting gastrectomy making the results difficult to interpret in the light of oncological safety. All other reports on omentum-sparing gastrectomy are from Eastern centers where the incidence of gastric cancer, stage distribution, and patient demographics differ from the West [3,4,5,6,7,8].

This study has several limitations. It was performed on a relatively small patient sample. Nevertheless, the necessary number of participants for a non-inferiority study with 80% power, a standard deviation of 5%, and a margin of error of 5% is 72 patients in each arm. In our paper, more than 90 patients remained in each arm after PSM. Another limitation was the mixed pathological tumor stage population. Most of the patients had advanced gastric cancer, making it safe to assume that our results can be generalized to patients with advanced gastric cancer. Lastly, the present paper is a retrospective study. The PSM could account for some of the selection bias. However, many subtle factors that have not been accounted for may have been missed. Therefore, performing a multi-institutional randomized controlled trial might be of significant value. Despite all these limitations, we believe that single-center studies provide a valuable source of information regarding the feasibility of laparoscopic omentum-preserving gastric cancer surgery in the West, where large-scale studies are much more challenging to produce.

The results from this single high-volume center support that the laparoscopic omentum-preserving gastrectomy was oncologically equivalent to open surgery with omentectomy, with less perioperative morbidity and faster postoperative recovery and discharge. Based on our results, we recommend the use of laparoscopic omentum-preserving gastrectomy in patients with early and advanced gastric cancer.