Due to the abundant LN drainage in the perigastric area, LN metastasis is prone to occur in GC patients, which will have an adverse impact on the treatment and patients’ prognosis . In order to improve the accuracy of clinical staging long-term prognosis of GC patients, increasing the detection of positive LNs is an important part of the treatment process and the key point of formulating follow-up treatment plan. Wang et al.  found that the increase in total number of LNs was more conducive to the discovery of positive LNs, especially micro LNs. Otherwise, with the increase of the number of detected LNs, the 5-year survival rate of GC patients also increased . Therefore, the acquisition of total LNs can be used as an independent risk factor for the prognosis of GC patients. However, the acquisition of LNs in GC patients is easily affected by many factors. For example, in patients with BMI more than 27, LNs are easy to hide in adipose layer and are not easy to separate from adipose tissue, which increases the difficulty of LN acquisition . In addition, the way of radical gastrostomy and the depth of tumor invasion will also affect the number of total LNs detected . Therefore, improving regional LN tracing method during operation and optimizing LN sorting scheme of isolated specimens are the key points to improve the total detection rate of LNs, especially micro LNs.
In this study, we used ICG as a fluorescent dye to label LNs. Due to the strong tissue penetration, a very small amount of ICG can show eye-catching fluorescence under near-infrared irradiation, which has great advantages for the labeling of LNs around GC, thus effectively displaying the drainage range of LNs . Therefore, ICG fluorescence labeling can effectively guide the surgeon to clean LNs, which is of great significance to improve the detection rate of total LNs. Moreover, in order to avoid the omission of LNs during operation, we established a professional LN sorting team. Through continuous theoretical study and practical operation, team members can effectively summarize and accumulate LN sorting experience and apply it to the continuous optimization of LN sorting methods, thus further improving the number of LNs detected . Therefore, the acquisition of total LNs, positive LNs, and micro LNs were significantly increased in ICG group, and the same results were also found in LN statistics of each substation. Otherwise, by analyzing the acquisition of total LNs and positive LNs in GC patients at different stages, we found that there was a significant positive correlation between them, indicating that increasing the sampling amount of LNs can better improve the detection rate of positive LNs, so as to carry out more accurate clinical staging for GC patients.
In order to further explore the effect of ICG on the detection rate of LNs in GC patients, we statistically analyzed the fluorescence staining of total LNs, micro LNs, and positive LNs. The results showed that fluorescent stained LNs account for 62% of total LNs and 52% of micro LNs, moreover, 74% of fluorescent stained LNs are positive LNs, suggesting that ICG tracing can better assist surgeon in collecting LNs and effectively improve the collection amount of positive LNs, so as to better stage patients. Otherwise, in terms of clinical treatment, the operation time, hospital stay, postoperative exhaust time, and postoperative feeding time of patients in ICG group were shortened to varying degrees, and the incidence of complications such as anastomotic fistula decreased to a certain extent, but no significant difference were found between two groups. The above results suggested that ICG tracing can assist the operator to complete LN dissection and show the blood supply of the anastomosis, which is conductive to improve patients’ clinical treatment reduce the occurrence of complications.
Accurate TNM staging is conducive to the formulation of postoperative chemotherapy and predict patients’ prognosis. Deng et al. analyzed the clinic pathological data of 2455 GC patients, and found that with the increase of LN number, patients’ TNM staging was more accurate, and their prognosis was better. We also found that after treatment, the levels of tumor markers in ICG group were better controlled, patients’ conditions were less prone to recur and metastasize, and their long-term survival rate was higher. Therefore, GC patients can better benefit from the increase in the number of harvested LNs, which can improve their prognosis.
ICG tracing combined with Ex vitro LN sorting is helpful to improve the detection number of total LNs and micro LNs in GC patients, as well as the number of positive LNs detected, which is of great significance to improve the accuracy of GC staging. Otherwise, about 62% of total LNs and 52% of micro LNs were found by ICG tracing, and the positive LNs stained by ICG account for 74% of total positive LNs. Therefore, ICG tracing plays an indispensable role in the sorting of GC LNs. In terms of prognosis, the levels of tumor markers in ICG group were better controlled, tumor recurrence and metastasis were less prone to occur, and patients’ mortality was significantly reduced. However, there are some deficiencies in this study. For example, whether ICG tracing combined with Ex vitro LN sorting is better than simple Ex vitro LN sorting has not been studied, and the study on relevant risk factors affecting LN detection is also not performed, which need to be improved in the follow-up study.