Introduction
Adenocarcinoma of the esophagogastric junction (AEG) refers to adenocarcinomas located within a range of 5 cm above and below the esophageal gastric junction (Siewert et al.
1987). AEG is an independent disease that is different from upper esophageal cancer and distal gastric cancer, and is divided into three types based on its location: Siewert type I refers to adenocarcinomas in which the tumor center is located within a range of 1–5 cm above the dentate line; Siewert type II, to adenocarcinomas located between 1 above and 2 cm below the dentate line; and Siewert type III, to adenocarcinomas located between 2 and 5 cm below the dentate line (Meng-xin and yanjunacang Shun-dong.
2021). The incidence rate of AEG has significantly increased worldwide (Manabe et al.
2022; Uhlenhopp et al.
2020). Currently, surgery is the only curative approach for AEG.
Surgical resection of AEG is mainly performed via the thoracic and abdominal approaches. Studies have shown that resection of Siewert type III AEG requires an abdominal approach, while Siewert type I tumor resection requires thoracotomy and lymph node dissection (D'journo X B.
2018). For Siewert type II AEG, surgeons often determine the surgical approach by combining the findings of preoperative gastroscopy, barium meal, CT, etc., with the location and extent of tumor invasion. Thoracic surgeons believe that a transthoracic approach can ensure sufficient length of the proximal margin, a negative upper margin, and effective mediastinal lymph node dissection (Peng et al.
2015), while gastrointestinal surgeons believe that the transabdominal approach can reduce the incidence of pulmonary complications and shorten postoperative hospital stay (Fei et al.
2021). Thus, the optimal surgical approach for Siewert type II AEG has always been controversial in clinical practice.
A key objective of AEG surgery is to ensure a negative surgical margin (Japanese gastric cancer treatment guidelines
2014), but the unique biological behavior of AEG causes cancer cells to infiltrate the esophageal side via the submucosal direction. With the routine staining and electronic endoscopy approach for localization, it is only possible to observe the lesion range on the mucosal surface. Therefore, it is impossible to determine whether the tumor has infiltrated the submucosal layer. In addition, as the staining time of commonly used staining agents, such as methylene blue, indigo carmine, indocyanine green, and other dyes, is relatively short, they can easily contaminate the surgical field over time and cause inaccurate localization (Price et al.
2000; Technology Committee et al.
2010; Takada et al.
2023; Nagami et al.
2018). If surgeons only determine the extent of tumor resection by manual observation or palpation during surgery, it is easy to overestimate the extent of resection of the esophageal length. This could lead to an increase in the risk of positive surgical margins, difficulty in reconstructing anastomoses, and increased surgical trauma, among other related problems.
The esophagus enters the abdominal cavity from the thoracic cavity at the esophageal hiatus, approximately at the level of the 10th thoracic vertebra (Kahrilas et al.
2008). Therefore, in the case of AEG lesions that invade the junction of the esophagus and stomach, the diaphragm may be involved. This might necessitate different surgical approaches. Alternatively, endoscopic ultrasonography (EUS) can be used to accurately detect the extent of submucosal infiltration of AEG and determine the extent of tumor invasion (Takamaru et al.
2020). Further, as an alternative staining agent, carbon nanoparticles have advantages such as stable properties and longer staining time compared to traditional staining agents, and no serious side effects have been reported yet (Wang et al.
2013). As a solution to overcoming these challenges associated with traditional approaches, this study explores preoperative EUS with carbon nanoparticle and titanium clip labeling as an alternative to traditional techniques for marking the tumor boundary and determining the extent of submucosal invasion of the tumor. In addition to EUS, abdominal radiography was used to determine the height of the titanium clip, and the surgical approach was predicted based on the relationship between the position of the titanium clip and the lower edge of the 10th thoracic vertebra. During surgery, the resection boundary was determined by palpating the titanium clip and observing the range of carbon nanoparticle black staining, to ensure a negative surgical margin.
Discussion
The incidence rate of AEG has been increasing every year. However, the unique anatomical location and biological behavior of Siewert type II AEG makes the selection of the surgical approach and determination of the resection range difficult. When planning and performing surgery for early Siewert type II type AEG, it is not possible to accurately determine the extent of invasion based on visual observation and palpation. Moreover, the limitations of traditional staining and labeling methods, as described in the introduction section, seriously affect intraoperative judgment. Surgeons often resect the lesion with a larger margin than required to ensure a negative surgical margin, and there are no standard clinical methods for determining the surgical approach. With regard to the surgical approaches, the transthoracic approach is more invasive and is associated with more complications and a higher postoperative mortality rate. In contrast, the transabdominal approach is associated with more pulmonary complications but a longer survival time (Kurokawa et al.
2013).
In response to the clinical issues regarding the selection of AEG surgical approaches and resection range discussed earlier, this study proposes a dual localization technique involving preoperative EUS-guided labeling with titanium clips and carbon nanoparticles. First, EUS was used to detect tumor invasion in the mucosal layer, submucosal layer, muscular layer, and serosal layer, as well as metastasis to important organs and lymph nodes. As previously published, EUS has great value for determining the scope of tumor invasion and TNM staging (Yong et al.
2013). Second, carbon nanoparticle staining has advantages over traditional staining methods: that is, it has greater stability, longer dyeing time, and no serious side effects. Our team has already reported the advantages of combining EUS technology with carbon nanoparticle staining in preoperative labeling and localization in the treatment of early-stage cancer (Yongwei et al.
2019). This study explored the addition of titanium clips that can be visualized under X-rays for the purpose of visually assessing the extent of invasion of tumor lesions before surgery.
For the selection of surgical approach, as the esophageal hiatus is approximately at the level of the 10th thoracic vertebra, the esophagus enters the abdominal cavity from the thoracic cavity. This study used the positional relationship between the titanium clip and the 10th thoracic vertebral body as the basis for determining the surgical approach: When the titanium clip was placed above the 10th thoracic vertebral body, the surgery was completed through a thoracic approach. When the titanium clip was placed below the 10th thoracic vertebral body, the surgery was completed through an abdominal approach. A combined thoracoabdominal approach was used when the clip was placed between the upper and lower edges of the 10th thoracic vertebral body. The final results show that the accuracy of this method for the prediction of surgical approach was 96.8%, which is significantly better than that of traditional judgment methods.
With regard to determining the length of tissue that needs to be resected above the tumor, the innovative use of titanium clip and carbon nanoparticle dual localization with EUS in this study was found to be useful for accurately detecting the range of invasion, including early tumors. That is, the dual localization technique used here allowed for precise localization of the actual infiltration boundary of the tumors while minimizing the probability of labeling failure. With only nanocarbon labeling, there is a small probability of the particles diffusing beyond the intended region or infiltrating too deep into the tissue, and this could have affected the assessment of the tumor. In addition, the lack of tactile feedback is not conducive to intraoperative positioning. If titanium clips are used alone for labeling, although the position of the titanium clip can be determined through imaging or intraoperative tactile feedback before surgery, there is still a small probability of the titanium clip detaching.
The unique biological features of AEG include its ability to infiltrate and metastasize widely, as well as invade the submucosal lymphatic network of the esophagus (Xiang
2012). The fifth edition of the Japan Gastric Cancer Convention advocates preoperative endoscopic labeling based on biopsy results of the tumor boundary for tumors that invade the esophagus, and examination of intraoperative frozen sections of the cutting edge is also performed to ensure R0 resection (Lei et al.
2018). In this study, continuous pathological sections were used to explore the infiltrating behavior of the tumors. The pathological results confirmed tumor-infiltrating behavior in all 60 cases. In the experimental group, no tumor-positive pathological samples of the upper cutting edge were found, and there was no significant difference in the incidence of postoperative complications compared to the conventional group. This indicates that the dual localization technology employed in the group has sufficient safety and reliability.
The main limitations of this study are its single-center setting and the small sample size. In the future, a multi-center study with a large sample size is required to demonstrate the reliability and effectiveness of the proposed dual localization technique. Another limitation is that there are no follow-up data on postoperative survival time, recurrence rate, and quality of life, as a result of which it is impossible to compare the prognosis of the two groups and determine the potential long-term benefits of this technique. A final limitation of this study is that patients with AED stage IIB and higher were not included because of the risk of titanium clip detachment after neoadjuvant chemotherapy. In the future, we plan to include patients who have gone neoadjuvant chemotherapy and explore if the dual labeling technique with titanium clips and carbon nanoparticles is also beneficial for exploring tumor regression behavior after neoadjuvant chemotherapy in this group of patients, as this could provide a basis for surgical resection after chemotherapy.
Conclusion
In summary, in patients with Siewert type II AEG, the dual localization technique with carbon nanoparticle staining and titanium clip placement under EUS before surgery can help determine the actual boundary of the lesion based on imaging findings, provide an objective basis for the selection of the surgical approach, and prevent the chances of excessive esophageal resection and tumor-positive margins during surgery. As per the current findings, it is a safe, stable, and reliable method, but further clinical studies with large sample sizes conducted across multiple centers, including randomized control trials, are still needed to demonstrate the effectiveness of this technology.
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