A randomized trial of combined indocyanine green and endoscopic ultrasound for lymph node evaluation in gastric cancer surgery

Introduction

According to the global cancer statistics for 2023, stomach cancer ranks among the top five malignant tumors in terms of both incidence and mortality (1). In our nation, the incidence and mortality rates of stomach cancer are rank fifth and third, respectively (2). The treatment of gastric cancer remains a significant challenge, with radical surgical resection currently being the most effective treatment option (3). Determining surgical margins and the extent of lymph node dissection has emerged as critical factors influencing prognosis. The approach to stomach cancer surgery has evolved (4).

The main metastatic pathway for gastric cancer is lymphatic metastasis. Factors affecting the survival rate of gastric cancer depend not only on the primary lesion but also on the presence of regional lymphatic metastasis. An increased number of examined lymph nodes correlates with a higher likelihood of detecting metastatic lymph nodes, resulting in more accurate and reliable staging and a reduced probability of overlooking metastatic lymph nodes (5,6). According to the 8th edition of the American Joint Committee on Cancer (AJCC) guidelines, at least 16 lymph nodes should be excised during radical gastric cancer surgery to ensure that the staging results are considered reliable (7). In patients with T1-3N0-1 gastric cancer, a greater number of dissected lymph nodes is associated with improved postoperative survival (8). Furthermore, the lymph node ratio (LNR) serves as an independent prognostic factor for gastric cancer (9). For early-stage gastric cancer, sentinel lymph node biopsy is critical for determining whether to extend lymph node dissection (10). Nevertheless, the extent of lymph node dissection is often influenced by the surgeon’s preference and experience. The widespread adoption of indocyanine green (ICG) fluorescence imaging technology has become pivotal in addressing this challenge (11).

ICG, a leading lymph node tracer, is one of the first dyes authorized for commercial use by the U.S. Food and Drug Administration (FDA). It is currently the only fluorescent contrast agent approved for clinical usage in our country, owing to its high sensitivity and safety (12). ICG has the capability to image blood vessels and can be used for real-time intraoperative vascular monitoring (13), as well as for assessing anastomotic blood flow perfusion to reduce the incidence of anastomotic leaks (14). The fluorescence properties of ICG enable the observation of stained tissues at a depth of up to 5 mm under infrared light, thereby enhancing the detection rate of lymph nodes within adipose tissue (15). Furthermore, it can be employed for preoperative submucosal injection to delineate the margins of lesions. The application of ICG imaging can increase the detection rate of lymph nodes, shorten surgery duration, reduce intraoperative bleeding, and diminish the likelihood of positive surgical margins (3). In comparison to conventional tracers such as carbon nanoparticles and methylene blue, ICG demonstrates significant advantages in terms of safety, sensitivity, and specificity, while also being more cost-effective (16-21). However, ICG is not without limitations. Although the yield of lymph nodes can be greatly increased by utilizing ICG, there remains a 46% false-negative rate for lymph nodes (22). These outcomes evidently impact surgical quality, undermine the validity of ICG use, and increase the risk of overlooking positive lymph nodes.

Endoscopic ultrasound (EUS) possesses unique advantages in the diagnosis and treatment of early gastric cancer. By providing high-resolution images, EUS can distinctly reveal the layered structure of the gastric wall, allowing for accurate assessment of tumor infiltration depth and extent, with an accuracy rate of up to 90% (23). In evaluating metastatic lymph nodes, the accuracy can reach 86% (24). Moreover, EUS offers several advantages during its application, such as low cost, flexible usability, and minimal environmental restrictions, in contrast to technologies like computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) which are often expensive, have limited applications, lack flexibility, and require prolonged examination times (25). Consequently, EUS demonstrates significant advantages in local tumor detection. Currently, EUS is commonly used for preoperative tumor diagnosis, staging, and endoscopic treatment of early-stage tumors (26-28). However, there are no definitive reports on the application of EUS for intraoperative navigation in gastric cancer, which would provide real-time visualization of tumor location and lymph node status. Therefore, this paper proposes the establishment of a multimodal precise navigation system that integrates EUS with ICG fluorescence imaging technology to create a joint navigation system. This system can real-time detect the tumor’s location, infiltration depth, and lymph node positivity in during surgery, thereby enabling precise navigation and treatment for gastric cancer surgeries. This study comprehensively assesses the feasibility of the navigation system in assisting lymph node detection and dissection during gastric cancer surgery by analyzing the effects of ICG combined with EUS on lymph node yield and pathological concordance. Preliminary in vitro results support this approach. We present this article in accordance with the CONSORT reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2654/rc).

Methods

Patients

This study randomly included 26 patients who underwent radical gastric cancer surgery at Northern Jiangsu People’s Hospital between September 1, 2024, and October 31, 2024. The patients were randomly divided into two groups: the ICG group (n=13), which utilized ICG fluorescence imaging technology during the surgery, and the non-ICG group (n=13), which did not employ this technology.

This pilot study was designed as an exploratory trial to evaluate the feasibility of the combined ICG-EUS approach. The inclusion period was limited to two months to align with institutional ethical approval validity and preliminary resource allocation. Randomization was performed using a computer-generated block sequence (block size =4) with allocation concealment via sealed opaque envelopes. Surgeons and pathologists were blinded to group allocation until data analysis.

The inclusion criteria were as follows: (I) age 18–80 years, regardless of gender; (II) patients diagnosed with gastric cancer through electronic gastroscopy; (III) patients assessed as eligible for radical gastric cancer surgery. The exclusion criteria included: (I) previous history of gastrointestinal tumor surgery or preoperative neoadjuvant therapy; (II) examination indicating advanced gastric cancer, rendering radical surgery impossible; (III) severe infection prior to surgery; (IV) history of other malignant tumors; (V) history of adverse reactions to previous ICG injection; (VI) pregnancy or breastfeeding.

All surgeries in this study were performed using laparoscopic approaches, with no open surgical cases included. The procedure was performed by two senior gastrointestinal surgeons, each with over 1,000 cases of experience in laparoscopic gastric cancer surgery experience carried out the procedure. All enrolled cases underwent standardized surgical procedures: Billroth II anastomosis with D2 lymphadenectomy, in line with the Japanese Gastric Cancer Treatment Guidelines (2021 edition). In the ICG group, the resected specimens were first examined by EUS to document tumor and lymph node characteristics. The specimens were then transported to the pathology department with standardized labeling (containing only patient ID). Under blinded conditions, pathologists retrieved lymph nodes based on anatomical location. Gross findings were cross-referenced with EUS results, and pathological findings served as the gold standard for evaluating tumor infiltration depth, internal echogenicity, and lymph node involvement (Figure 1). Surgeons were aware of ICG administration but blinded to preoperative EUS findings and expected metastasis status; pathologists evaluated lymph node metastasis based solely on histology, with ICG staining information excluded from specimen labels, though staining might be visually identifiable.

Figure 1 The surgical and sample processing procedure for the ICG group. During the surgery, a total of 4 mL (1 mL at each of the four key points) of ICG is injected subserosally around the gastric lesions through laparoscopy at four key points around the tumor. Thirty minutes later, intraoperative fluorescence imaging and near-infrared imaging are performed to observe the distribution of ICG. The ICG staining determines the surgical scope. Postoperatively, the excised tissue samples are placed in saline and scanned with an endoscopic ultrasound to collect images. Subsequently, pathological analysis (including H&E staining and CK19 immunohistochemistry) is performed for comparative validation. The pathological results serve as the gold standard to evaluate tumor infiltration depth, internal echo, and lymph node infiltration. CK19, cytokeratin 19; H&E, hematoxylin-eosin; ICG, indocyanine green; LN, lymph node; NIR, near-infrared.

Ethical statement

This study was approved by the Institutional Review Board of Northern Jiangsu People’s Hospital (No. 2024ky211) and registered with the Chinese Clinical Trial Registry (ChiCTR2400090495). The trial was conducted in accordance with the Declaration of Helsinki and its subsequent amendments and the Good Clinical Practice guidelines. All patients provided written informed consent prior to their inclusion in the trial.

ICG usage

To prepare a 1.25 mg/mL ICG solution, dissolve 25 mg of ICG (Dandong Yichuang Pharmaceutical Co., Ltd., Dandong, China) in 20 mL of saline to prepare a 1.25 mg/mL ICG solution. During the procedure, inject a total of 4 mL (1 mL at each of the four key points) subserosally around the gastric lesions via a laparoscope. After 30 minutes interval, perform intraoperative fluorescence imaging and near-infrared (NIR) imaging to observe the distribution of ICG and determine the surgical scope based on the staining pattern. ICG fluorescence was utilized to identify lymph nodes within the planned resection field, ensuring that no nodes outside standard anatomical boundaries were excised. Postoperative ex vivo tissue samples underwent fluorescence imaging and NIR imaging for further analysis.

EUS

The EndoEcho system is equipped with the Olympus PREMIER PLUS, featuring an ultrasound probe with a diameter of 2.2 mm and a scanning range of 360°; the Olympus probe: UM-3R 20MHZ.

After gastric cancer surgery, collect ex vivo specimens distinguishing between normal tissue, tumor tissue, vascular adipose tissue, and lymph node tissue. Place the collected tissue specimens in saline, and utilize EUS to scan and capture images. All procedures are conducted under the guidance of a professional physician, carefully observes the depth of tumor infiltration, internal echoes, and lymph node infiltration. Ultimately, the assessment is made by two experienced physicians. The criteria for EUS to determine lymph node metastasis refer to the specified documents, specifically: hypoechogenicity, short-axis to long-axis ratio >0.5, irregular borders, absence of hilar structure, or accompanied by calcification/liquefaction (29). EUS assessments in this stage were based on ex vivo specimens from the ICG group, aiming to preliminarily verify the feasibility of combined ICG and EUS for lymph node detection.

Hematoxylin-eosin (H&E) staining & cytokeratin 19 (CK19) immunohistochemistry

Tissue samples were fixed in 4% paraformaldehyde, followed by routine dehydration and clearing, and subsequently embedded in paraffin blocks. The section thickness was maintained at 4 µm, and staining was conducted using the conventional H&E staining method. The specific steps are as follows: first, dry the paraffin sections were dried in a temperature-controlled oven, followed by deparaffinization and rehydration. Next, the sections were immersed in a hematoxylin solution and stained for 5 to 10 minutes, followed by rinsing with water. The sections were transferred to an eosin solution and stained for approximately 2 to 3 minutes. Finally, the sections were dehydrated, cleared, and mounted, allowing for morphological structure is observed under a microscope. Histological assessment included H&E staining as the gold standard, with CK19 immunohistochemistry used adjunctively to confirm ambiguous micrometastases or isolated tumor cells.

Statistical analysis

All data were analyzed statistically using SPSS 27.0 (IBM SPSS, Chicago, IL, USA). Quantitative data are presented as mean ± standard deviation (mean ± SD) and group comparisons were performed using independent samples t-test or Mann-Whitney U test. Qualitative data are expressed as frequency and percentage, with intergroup differences are analyzed using the Chi-squared test. All statistical tests were conducted as two-tailed tests, with a P value <0.05 considered statistically significant. To assess the consistency between ICG and EUS detection, the kappa coefficient (κ) was calculated. The interpretation standards for the kappa value are as follows: slight (0.01–0.20), fair (0.21–0.40), moderate (0.41–0.60), substantial (0.61–0.80), and almost perfect (0.81–1.00).

Results

Baseline characteristics

This is an exploratory trial; randomization was used primarily to balance baseline characteristics, enabling reliable assessment of the preliminary effects of the ICG + EUS system on lymph node detection, rather than validating hard clinical endpoints typical of confirmatory randomized controlled trials (RCTs) (Figure S1).

We collected preoperative baseline information from two groups of patients and analyzed the collected data. The baseline characteristics of the patients were presented in Table 1. The ages and body mass index (BMI) of the two groups of patients both conform to a normal distribution (age: Shapiro-Wilk =0.957, 0.980, P=0.706, 0.981>0.05; BMI: Shapiro-Wilk =0.911, 0.918, P=0).

The surgical procedure using ICG navigation

We outline the application procedure of ICG for radical gastric cancer surgery in Figure 2. Specifically, the subserosal injection of ICG at four strategic locations surrounding the gastric lesion area is depicted Figure 2A. The fluorescence signal in the lesion area becomes readily visible thirty minutes post-injection using fluorescence imaging equipment (Figure 2B). Figure 2C illustrates that the lesion region appears distinctly green when observed in NIR imaging mode.

Figure 2 Procedures for ICG Injection and resulting fluorescence imaging status. (A) The ICG injection situation, with the red arrow indicating the ICG injector; (B,C) the ICG staining of the lesion area under fluorescence mode and NIR mode, respectively; (D-F) the lymph node staining; (G-I) Visualization of ICG-Labeled lymph nodes under ex vivo conditions. The red arrows indicate ICG-labeled lymph nodes. ICG, indocyanine green; NIR, near-infrared.

Pathology confirmed malignancy in ICG-negative nodes that were visually suspicious (Figure 3), as well as in a subset of ICG-positive nodes (Figure 3A,3C). We hypothesize that this might be because ICG is unable to enter the interior of the lymph nodes because of lymphatic blockage. However, conversely, ICG-positive nodes without pathological evidence of metastasis (Figure 3B,3D) underscored the technique’s limitations in specificity. We thoroughly examined the lymph nodes that tested positive and negative for ICG imaging in order to better understand this phenomenon (Figure 2G-2I).

Figure 3 The red arrow in (A) shows the ICG non-stained metastatic lymph nodes, (C) is the H&E staining result of the lymph nodes. The yellow arrow in (B) indicates the lymph nodes that were ICG positive but did not show metastasis, (D) is the H&E staining result of these lymph nodes. Magnification: 20×. H&E, hematoxylin-eosin; ICG, indocyanine green.

Comparison of the number of lymph nodes between the ICG group and the non-ICG group

We conducted a statistical analysis of the surgical outcomes between the ICG group and the non-ICG group (Table 2). To evaluate the feasibility of the combined navigation system, this study conducts analysis from two key dimensions: first, lymph node yield, which reflects the quality of surgical dissection; second, concordance with pathological results, which reflects diagnostic accuracy. The average number of lymph nodes excised in the ICG group was 41.15, which was significantly higher than the 26.62 observed in the non-ICG group, demonstrating a statistically significant difference (P=0.024<0.05). Although the ICG group exhibited a greater mean number of positive lymph nodes compared to the non-ICG group, there was no statistically significant difference was observed in the counts of positive lymph nodes between the two groups (P=0.437>0.05). This indicates that while ICG has not yet shown a definitive advantage in the retrieval of positive lymph nodes, its application in surgical procedures can significantly enhance the total number of lymph nodes removed.

ICG combined with EUS

The lymph node detection efficacy of ICG revealed a detection rate of 85.78%, a coverage rate of 58.95%, and a concordance with pathological results of 0.77. When ICG was combined with EUS, the detection rate improved to 94.71%, the coverage rate increased 67.92%, and the concordance with pathological data reached 0.89. The detection and coverage rates of lymph nodes were significantly superior when ICG was used in conjunction with EUS compared to the use of ICG alone (P<0.05) (Table 3).

Subsequently, we performed EUS examinations on the ex vivo samples from the ICG group and evaluated the T staging based on tumor infiltration depth. The sensitivity of EUS in determining the depth of infiltration is 84.62%, the specificity is 92.31%, and the consistency is good (Kappa =0.76) (Table 4). These findings support the role of EUS in assisting the combined ICG-EUS navigation system to define tumor boundaries, thereby providing a reference for determining the scope of lymph node dissection, which is indirectly relevant to the core goal of evaluating lymph node detection efficacy.

Comparison between ultrasonographic endoscopic images and pathological tissue morphology

Normal tissue

In the ultrasonographic examination of ex vivo stomach wall tissues and the larger omentum, we employed precise techniques to assess the ultrasonographic characteristics of these tissues. Ultrasonography was performed on the serosal and mucosal layers of the stomach wall tissues individually, as illustrated in Figure 4A-4D. The images clearly depict the anatomical layers of the gastric wall, with the mucosal and serosal layers appearing as uniform, loud echoes in the ultrasonographic images. In contrast, the muscularis mucosae and muscularis propria exhibit comparatively lower echoes intensities. The submucosal layer is represented as a prominent echo area, reflecting the acoustic properties s and structural density of the tissues.

Figure 4 Comparison between ultrasonographic endoscopic images and pathological tissue morphology. (A-D) Ultrasound images and pathological H&E-stained images of normal gastric wall tissue. The blue arrows indicate the fixed samples. Magnification: 2×. (E,F) The morphology of adipose tissue under ultrasound and in pathological sections. (G,H) The morphology of subcutaneous blood vessels under ultrasound and in pathological sections. The red arrows indicate the blood vessels. H&E stain; 2× magnification. H&E, hematoxylin-eosin.

During the ultrasonographic endoscopy of the larger omentum, we observed that adipose tissue (as shown in Figure 4E,4F) produced a consistent high-echo band in the ultrasonographic images, indicating of the granular aggregation of adipocytes. Figure 4G,4H distinctly illustrate the arterial structures within the adipose tissue, appearing as a transparent anechoic regions in the ultrasonographic endoscopic images, which correspond to the morphology of the vascular cross-sections observed in pathological specimens. This finding demonstrates that ultrasonography can accurately depict the anatomical position and structure of blood vessels.

The observations derived from these ultrasonographic images not only intuitively reflect the acoustic properties of the tissues but also correlate significantly with the final diagnostic results from pathological sections, thereby affirming the accuracy and reliability of ultrasonographic imaging technology in medical diagnostics. Moreover, ultrasonography provides substantial diagnostic advantage in evaluating normal tissue architecture owing to its non-invasive nature and operational simplicity.

Tumor tissue

Our investigation into the ultrasonographic scanning of tumor tissue samples revealed that the ultrasonographic features of tumor tissues markedly differ from those of normal tissues (Figure 5). Figure 5A illustrates the disordered layered structure of the stomach wall, characterized by indistinct borders, uneven echo distribution, and a surface marked by irregular high-echo regions. These ultrasonographic characteristics align with the clinical diagnosis of ulcerative adenocarcinoma (Figure 5B) and are further corroborated by immunohistochemistry findings (Figure 5C).

Figure 5 The results of comparing the images of lesions scanned by endoscopic ultrasound with pathological images are presented. The orange arrows indicate the correspondence between the EUS-based diagnosis and the pathological diagnosis. The red boxes indicate the magnified area of the pathological image. (B,E,H) H&E stain; (C,F,I) IHC for CK19 stain. CK19, cytokeratin 19; EUS, endoscopic ultrasound; H&E, hematoxylin-eosin; IHC, immunohistochemistry.

The ultrasonographic images, shown in Figure 5D,5G, illustrate the disorganization of the stomach wall structure and indistinct layers, with certain regions of the gastric wall merging, localized thickening, and heterogeneous echogenicity, which align with the pathological findings (Figure 5E,5H). Endoscopic ultrasonography offers a significant advantages in evaluating tumor tissues, as its scanning depth can traverse the entire stomach wall, thereby elucidating the extent of gastric cancer invasion more clearly and promptly. These findings underscore the pivotal importance of endoscopic ultrasonography in the identification and staging of gastric cancer, providing essential diagnostic information for clinical practice.

Lymph nodes

In our comprehensive examination of tumor metastasis, we found that endoscopic ultrasonography (EUS) provides significant advantages in diagnosing metastatic lymph nodes, however it is constrained in detecting micrometastatic lymph nodes (Figure 6). Figure 6A illustrates an EUS image that reveals the lymph node as a homogeneous, oval hypoechoic region with an intact capsule and well-defined margins, while the hilum structure is identifiable. Subsequent histological investigations unexpectedly revealed that these lymph nodes had undergone micrometastasis. In contrast to micrometastatic lymph nodes, broadly metastatic lymph nodes exhibit distinct features on EUS images: the hilum structure is absent, and there are patchy hyperechoic regions or reduced tissue echogenicity (as shown in Figure 6D,6G). In Figure 6D, the lymph node capsule remains discernible, although its thickness has markedly increased, the hilum structure is unidentifiable, and the tissue echogenicity has diminished. In Figure 6G, the lymph node is presented as a patchy hyperechoic region lacking a capsule, indicative of EUS characteristics associated with metastatic lymph nodes. Subsequent pathological H&E staining and immunohistochemical investigation corroborated the findings observed via EUS. The use of ex vivo lymph nodes in this study limited evaluation of blood flow status, thereby constraining the comprehensive assessment of lymph node metastases.

Figure 6 Correlation between EUS-based lymph node morphology and pathological diagnosis. (A-C) Micro-metastatic lymph nodes, while (D-I) are widely metastatic lymph nodes. The red arrows indicate the judgment results of metastasis, and the blue arrow indicates the fixatives used for the fixed specimens. The red boxes indicate the correspondence between the EUS-based diagnosis and the pathological diagnosis. (B,E,H) H&E stain; (C,F,I) IHC for CK19 stain. CK19, cytokeratin 19; EUS, endoscopic ultrasound; H&E, hematoxylin-eosin; IHC, immunohistochemistry.

Discussion

In the pursuit of improving surgical efficiency and enhancing patient prognosis, the application of lymph node tracers has made significant advancements. Commonly utilized lymph node tracers include nanoparticle carbon, methylene blue, and ICG. Each of these tracers can assist clinicians in distinguishing between normal tissue and lymph nodes, thereby maximizing the number of metastatic lymph nodes removed, which in turn is beneficial for disease staging and prognosis. Notably, nanoparticle carbon selectively targets the lymphatic system rather than the vascular system. A multicenter study has demonstrated that nanoparticle carbon staining of sentinel lymph nodes in early gastric cancer achieves a sensitivity, specificity, and accuracy exceeding 90% (16). Furthermore, a meta-analysis indicated that the use of nanoparticle carbon—a lymphatic tracer that accumulates in regional lymph nodes after peritumoral injection, aiding their visual identification—in colorectal cancer surgery increases the average of lymph nodes removed by 6.15. However, nanoparticle carbon is not without its limitations; Firstly, it is considerably more expensive, costing over ten times that of ICG and methylene blue (17). Secondly, in terms of application, excessive injection of nanoparticle carbon can lead to overly dark staining, which may impair the surgical field. Lastly, and most importantly, although no adverse reactions to nanoparticle carbon have been reported so far, numerous cell and in vivo animal studies indicate that nanoparticle carbon exhibits cytotoxic and genotoxic effects, with a tendency to accumulate in the body and undergo slow metabolic degradation (18). Methylene blue is also a commonly used lymph node tracer. Compared to nanoparticle carbon, methylene blue is inexpensive, highly operable, and has a wide range of applications. However, due to the absence of sulfonate groups and its inability to bind with plasma proteins, methylene blue exhibits lower specificity (19). Furthermore, the safety of methylene blue remains controversial, as it has been shown to cause cardiac abnormalities and neurotoxic outcomes in patients using serotonergic drugs (20). As a standout tracer, ICG possesses unique advantages. Its small molecular weight prevents absorption in the gastrointestinal tract. Following intravenous injection, ICG quickly binds to serum albumin, after which it is secreted into the biliary system and excreted from the liver in its unbound form. This process ensures that ICG is not absorbed by the body, thereby guaranteeing the safety of its use (21). Previous studies have demonstrated that the use of ICG in gastric cancer surgery significantly increases the total number of lymph nodes harvested and reduces the non-compliance rate of lymph nodes, all without prolonging surgical time or increasing postoperative morbidity. However, the clinical utility of ICG is limited by its instability and high protein-binding affinity, resulting in a short half-life (plasma t1/2 =2–4 minutes) (30). ICG injection timing may impact results: shorter intervals (e.g., 1 hour preoperatively) prioritize stronger signals, while longer intervals (e.g., 24 hours) may enhance selective accumulation in metastatic nodes, with both aiming to optimize visualization. Notably, the utility of fluorescent agents in lymph node identification, as demonstrated with ICG in our study, lays a foundation for future exploration of targeted fluorescent contrast agents that bind to cancer-specific molecular markers, with potential to further refine metastatic node detection.

Endoscopic ultrasonography integrates endoscopy with a miniature ultrasound probe, facilitating the direct detection of mucosal surface lesions under endoscopic visualization. Concurrently, real-time ultrasound scanning enables the assessment of the involvement of the various layers of the intestinal wall and their relationship with surrounding tissues. This technique is also effective in evaluating the size, shape, histological type, origin layer, and depth of invasion of the lesions (26). Endoscopic ultrasonography demonstrates a sensitivity of 86% in distinguishing demonstrates the benign and malignant lymph nodes (31). Compared to CT, MRI, and PET, endoscopic ultrasonography presents several advantages, including flexibility, real-time imaging, low cost, wide applicability, absence of radiation, and ease of visualization. Furthermore, endoscopic ultrasonography can evaluate blood flow status in vivo, which may be beneficial for monitoring blood flow following gastrointestinal anastomosis. In terms of diagnostic accuracy and sensitivity, endoscopic ultrasonography performs comparably to CT (32). The combination of ICG and endoscopic ultrasonography to establish a multimodal intraoperative navigation system could potentially enable real-time and accurate identification of lesion sites, delineation of the resection boundaries, and assist surgeons in selecting surgical approaches, thereby achieving precise radical treatment for gastric cancer in the future.

This study is a preliminary exploration, and EUS assessments used ex vivo specimens to focus on the basic efficacy of technical synergy; subsequent studies will adopt clinically relevant intraoperative scanning methods to further verify its application value. There are several limitations in this study. First, there is currently not standardized protocol for the use and injection of ICG. Different injection methods, including preoperative submucosal injection during gastroscopy and intraoperative subserosal injection, may yield different results due to variations in tumor location and size, which could affect the accuracy of lymph node tracking. In this study, we used intraoperative subserosal injection, but further comparative studies are needed to assess the differences between various injection methods. A potential limitation is that complete blinding was challenging: surgeons knew of ICG use, and pathologists might identify stained nodes. However, procedural measures were taken to minimize bias. Second, this study is still in the ex vivo analysis of surgical specimens. As a pilot study, the sample size was limited, and no a priori power calculation was conducted. Future trials will incorporate formal sample size estimation based on these preliminary results. Further in vivo experiments are required to validate the reliability of the results and assess the feasibility of the technique for eventual clinical application. Third, endoscopic ultrasonography has limitations in identifying micrometastatic lymph nodes and cannot completely replace histopathological examination, which remains the gold standard. Therefore, further improvements in the technology are needed to enhance the ability to identify micrometastatic lymph nodes. In conclusion, although this study has made some progress in exploring tumor metastasis, more research is needed to overcome the existing limitations and improve both diagnostic accuracy and clinical applicability.

Conclusions

This study demonstrates that the multimodal intraoperative navigation system established by combining ICG and endoscopic ultrasonography is feasible for use in radical gastrectomy for gastric cancer. This technology has the potential to enhance the quality of gastric cancer surgeries, increase lymph node yield, and improve the accuracy of positive lymph node identification, thereby providing a new direction for precise intraoperative navigation. Therefore, the combination of ICG and endoscopic ultrasonography holds great promise for future clinical applications.

Acknowledgments

We thank our colleagues for their assistance and constant support.

Footnote

Reporting Checklist: The authors have completed the CONSORT reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2654/rc

Trial Protocol: Available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2654/tp

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2654/dss

Funding: This work was supported by Postgraduate Research & Practice Innovation Program of Jiangsu Province (No. SJCX25_1552), Social Development Project of Key R & D Plan of Jiangsu Provincial Department of Science and Technology (No. BE2022773). The funding bodies had no role in the design of the study; in the collection, analysis, and interpretation of the data; and in the writing the manuscript.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2654/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The trial was conducted in accordance with the Declaration of Helsinki and its subsequent amendments and the Good Clinical Practice guidelines. The study was approved by the Medical Ethics Committee of Northern Jiangsu People’s Hospital (No. 2024ky211). All patients provided written informed consent prior to their inclusion in the trial.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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