Techniques and Current Role of Sentinel Lymph Node (SLN) Concept in Gastric Cancer Surgery

Preclinical evaluation of sentinel node localization in the stomach via mannose-labelled magnetic nanoparticles and indocyanine green

BACKGROUND

Gastrectomy with extended (D2) lymphadenectomy is considered standard of care for gastric cancer to provide the best possible outcomes and pathologic staging. However, D2 gastrectomy is a technically demanding operation and reported to be associated with increased complications and mortality. Application of sentinel lymph node (SLN) concept in gastric cancer has the potential to reduce patient morbidity; however, SLN techniques are not established for gastrectomy, in part due to lack of practical tracers. An effective and convenient tracer with enhanced SLN accumulation is critically needed.

METHODS

Mannose-labelled magnetic tracer 'FerroTrace' and fluorescent dye indocyanine green (ICG) were injected laparoscopically into the stomach submucosa of 8 healthy swine under general anaesthesia. Intraoperative fluorescence imaging was used to highlight draining lymphatic pathways containing ICG, while preoperative T2-weighted MRI and ex vivo magnetometer probe measurements were used to identify nodes containing FerroTrace. Lymphadenectomy was performed either robotically (n = 2) or via laparotomy (n = 6).

RESULTS

Mixing ICG and FerroTrace ensured concurrence of fluorescent and magnetic signals in SLNs. An initial trial with robotic dissection removed all magnetic LNs (n = 4). In the subsequent laparotomy study that targeted all ICG-LNs based on intraoperative fluorescence imaging, dissection removed an average of 4.7 ± 1.2 fluorescent, and 2.0 ± 1.3 magnetic LNs per animal. Both MRI and magnetometer detected 100% of SLNs (n = 7). FerroTrace demonstrated high specificity to SLNs, which contained 76 ± 30% of total lymphotropic iron, and 88 ± 20 % of the overall magnetometer signal.

CONCLUSIONS

Through utilisation of this dual tracer approach, SLNs were identified via preoperative MRI, visualised intraoperatively with fluorescence imaging, and confirmed with a magnetometer. This combination pairs the sensitivity of ICG with SLN-specific FerroTrace and can be used for reliable SLN detection in gastric cancer, with potential applications in neoadjuvant therapy.

Stannous colloid mixed with indocyanine green as a tracer for sentinel lymph node navigation surgery

The combined use of a vital dye and radioactive colloid reportedly performs better in detecting sentinel lymph nodes (SLNs) for cancers than the use of either of them alone. However, especially for gastric cancer, two endoscopic procedures are required to administer these two tracers, which burdens the patients and practitioners. Here we propose the use of stannous colloid (SnC) mixed with indocyanine green (ICG) as a new mixed tracer (SnC-ICG); its characteristics were investigated in vivo and in vitro to estimate its usefulness for SLN navigation. The tracers were administered to rats and the accumulation of radioactivity and/or near-infrared fluorescence were evaluated in the regional lymph nodes (LNs) using single positron emission computed tomography and near-infrared fluorescence imaging, respectively. SnC-ICG showed significantly better clearance from the injection site and better migration to primary LNs than the single administration of SnC or ICG aqueous solution. SnC-ICG demonstrated a wide particle size variability, stabilized to 1200-nm upon the addition of albumin in vitro; These properties could contribute to its behavior in vivo. The use of SnC-ICG could contribute better performance to detect SLNs for gastric cancer with less burden on both patients and medical practitioners.

Detection Rate and Prognosis of Lymph Nodes in Gastric Cancer Using Nano Carbon Combined with In Vitro Anatomical Sorting

In this study, we are going to investigate the effect of nano carbon combined with ex vitro anatomical sorting on the detection rate of lymph nodes (LNs) in gastric cancer (GC) along with the analysis of the correlation between LNs detection rate and patients’ prognosis. The clinical data of patients undergoing radical gastrectomy in Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University from January 2018 to January 2019 were examined retrospectively. According to whether they adopt nano carbon tracing and specimen sorting method, patients were divided into nano carbon and control groups. The respective rate of detection and correlation of total and positive LNs, respectively, clinical treatment, tumor marker level, and long-term prognosis were matched between these groups. At the same time, the effects of the nano carbon tracer on the detection of total and positive LNs were evaluated. In nano carbon group, more LN specimens could be detected, and the number of positive LNs increased significantly. In addition, in patients with different infiltration stages and LN substations, more LNs could be detected in the nano carbon group for examination, and the detection rate of LNs with diameter less than 5 mm was also more. Furthermore, LNs (preferably positive in number) were correlated positively with the attained LNs number. Otherwise, the use of nano carbon suspension could better label LNs in each substation, especially N1 station, and improve micro-LN detection rate. At the same time, the positive metastasis rate in black-stained LNs was higher (31.67% vs. 13.51%). In relation to the clinical prognosis, CEA’s level, i.e., CA199 and CA125, in the nano carbon group is controlled more effectively. Their condition was not easy to progress and relapse, and their mortality was further reduced. As a result, nano carbon, coupled with ex vitro anatomical sorting, may considerably enhance the detection rate of total and positive LNs, thereby improving the accuracy of clinical staging in GC patients, which has a good influence on their long-term prognosis.

Misclassification of nodal stage in gastric cancer: 16 lymph nodes is not enough

Background

In gastric cancer, nodal stage plays an important role. Insufficient lymph node harvesting or incomplete examination may lead to misclassification and affect postoperative strategy and group survival. This study’s objective was to determine the minimum number of examined lymph nodes needed in gastric cancer and compare this to the minimum lymph node count according to the current Union for International Cancer Control (UICC) classification using real world data.

Methods

Based on anatomical data, expected mean lymph node counts and their 95% confidence intervals for complete D2 lymphadenectomy were calculated. Using stochastic analysis, a threshold for correct classification in 95% of cases was determined. Survival data of nodal negative gastric cancer patients was extracted from the Surveillance, Epidemiology, and End Results (SEER)-Database for 2010–2017. Patients reaching at least the calculated theoretical threshold were compared to the minimum threshold according to the current UICC classification.

Results

The expected lymph node count was 30 (95% CI: 28–32; range 17–52), corresponding to a 27 lymph nodes. In nodal negative patients with exactly 16 and at least 27 examined lymph nodes, relative 5 year survival was 79 and 89% in T1/T2 and 39 and 64% T3/T4 gastric cancer, respectively. Theoretically, when only 16 lymph nodes are analyzed, nodal negative staging may be incorrect in up to 47% of cases.

Conclusions

A minimum threshold of 16 examined lymph nodes cannot be justified. Retrospective analysis confirmed systematic misclassification of patients with insufficient lymphadenectomy in nodal negative gastric cancer patients. Correct lymphadenectomy and thorough examination of the surgical specimen is mandatory.

Ultrastaging Using Ex Vivo Sentinel Lymph Node Mapping and One-Step Nucleic Acid Amplification (OSNA) in Gastric Cancer: Experiences of a European Center

Simple Summary

In this study, the effectiveness of One-step nucleic acid amplification (OSNA) in combination with ex vivo SLN mapping is compared with conventional histology including immunohistochemistry. OSNA lymph node evaluation has been performed in 41 gastric cancer cases. It showed a high effectiveness with sensitivity, specificity, and accuracy rates of 85.4%, 93.5%, and 92.4%, respectively The LN status could be predicted in 40 cases and led to upstaging in three cases (14%). The OSNA method proved its potential to increase the sensitivity of metastases detection.

Abstract

Background: In this study, the effectiveness of One-step nucleic acid amplification (OSNA) in combination with ex vivo SLN mapping is compared with conventional histology including immunohistochemistry. Methods: LNs were retrieved from gastrectomy specimens in an unfixed state. After ex vivo SLN mapping using methylene-blue, LNs were sliced to provide samples for histology and OSNA. Results: In total, 334 LNs were retrieved in the fresh state from 41 patients. SLN detection was intended in 40 cases but was successful in only 29, with a correct LN status prediction in 23 cases (79%). Excluding one case out of 41 with a failure likely caused by a processing error, OSNA showed a high effectiveness with sensitivity, specificity, and accuracy rates of 85.4%, 93.5%, and 92.4%, respectively. The LN status could be predicted in all but one case, in which the single positive LN was not eligible for OSNA testing. Moreover, OSNA evaluation led to upstaging from N0 to N+ in three cases (14%). Conclusion: The ex vivo SLN protocol used resulted in a relatively poor detection rate. However, the OSNA method was not hampered by this detection rate and proved its potential to increase the sensitivity of metastases detection.

Recent updates and current issues of sentinel node navigation surgery for early gastric cancer

With the increase in the incidence of early gastric cancer (EGC), several endoscopic and laparoscopic approaches, such as endoscopic submucosal dissection and function-preserving gastrectomy, have been accepted as standard treatments. Sentinel node navigation surgery (SNNS) is an ideal surgical option for preservation of most parts of the stomach and consequent maintenance of normal gastric function to improve quality of life in patients with EGC. Although many previous studies and clinical trials have demonstrated the safety and feasibility of the sentinel node concept in gastric cancer, the clinical application of SNNS is debatable. Several issues regarding technical standardization and oncological safety need to be resolved. Recently several studies to resolve these problems are being actively performed, and SNNS might be an important surgical option in the treatment of gastric cancer in the future.

Global updates in the treatment of gastric cancer: a systematic review. Part 2: perioperative management, multimodal therapies, new technologies, standardization of the surgical treatment and educational aspects

Gastric cancer is the fifth malignancy and the third cause of cancer death worldwide, according to the global cancer statistics presented in 2018. Its definition and staging have been revised in the eight edition of the AJCC/TNM classification, which took effect in 2018. Novel molecular classifications for GC have been recently established and the process of translating these classifications into clinical practice is ongoing. The cornerstone of GC treatment is surgical, in a context of multimodal therapy. Surgical treatment is being standardized, and is evolving according to new anatomical concepts and to the recent technological developments. This is leading to a massive improvement in the use of mini-invasive techniques. Mini-invasive techniques aim to be equivalent to open surgery from an oncologic point of view, with better short-term outcomes. The persecution of better short-term outcomes also includes the optimization of the perioperative management, which is being implemented on large scale according to the enhanced recovery after surgery principles. In the era of precision medicine, multimodal treatment is also evolving. The long-time-awaited results of many trials investigating the role for preoperative and postoperative management have been published, changing the clinical practice. Novel investigations focused both on traditional chemotherapeutic regimens and targeted therapies are currently ongoing. Modern platforms increase the possibility for further standardization of the different treatments, promote the use of big data and open new possibilities for surgical learning. This systematic review in two parts assesses all the current updates in GC treatment.

Burgeoning study of sentinel-node analysis on management of early gastric cancer after endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) represents an organ-preserving alternative to surgical resection of early gastric cancer. However, even with ESD yielding en-bloc resection specimens, there are concerns regarding tumor spread such as with larger lesions, ulcerated lesions, undifferentiated pathology and submucosal invasion. Sentinel node navigational surgery (SNNS) when combined with ESD offers a minimally invasive alternative to the traditional extended gastrectomy and lymphadenectomy if lack of lymph node spread can be confirmed. This would have a clear advantage in terms of potential complications and quality of life. However, SNNS, though useful in other malignancies such as breast cancer and melanoma, may not have a sufficient sensitivity for malignancy and negative predictive value in EGC to justify this as standard practice after ESD. The results of SNNS may improve with greater standardization and more involved dissection, technological innovations and more experience and validation such that the paradigm for post-ESD resection of EGC may change and include SNNS.