Prognostic value of lymph node micrometastasis in esophageal cancer: A systematic review and meta-analysis

Sentinel Lymph Node Mapping in Esophageal Cancer: Current Status and Future Directions

OBJECTIVE

This review provides a comprehensive discussion about the importance of adequate lymphadenectomy, its anatomic and oncologic significance, principles and rationale of sentinel lymph node mapping, current evidence stratified by tracer substrate, challenges, and future directions. Esophageal cancer has one of the worst cancer-related survival rates, and nodal status is the single most significant prognostic factor. Submucosal penetration generally demands esophagectomy, often following neoadjuvant therapy in the presence of deeper extension. Guidelines recommend resecting ≥15 lymph nodes. Variability in surgical approach and dissection in concert with aberrant esophageal lymphatic anatomy make adequate lymphadenectomy difficult.

METHODS

A narrative review was conducted to explore existing literature regarding lymphadenectomy with its requisite anatomic and oncologic significance in esophageal cancer, as well as the rationale for and present state of sentinel lymph node mapping stratified by substrates. Tables and figures were constructed by the authors using Microsoft Office applications and Biorender software, respectively.

RESULTS

Sentinel lymph node mapping exploits the tumoral lymphatic network to identify the nodes most prone to metastasis, directing further dissection. Targeting sentinel lymph nodes with dyes, radiotracers, or hybrid tracers can assist surgeons with lymphadenectomy, potentially improving staging accuracy and personalizing care to individual anatomy.

CONCLUSIONS

While this approach would benefit from larger studies and long-term data, early evaluations suggest improved detection of metastases outside the en bloc field without significantly increasing morbidity.

[Evidence for the extent and oncological benefit of lymphadenectomy for esophageal cancer]

The prognosis for esophageal cancer is determined in particular by the depth of infiltration (T stage) and lymph node metastasis (N status). In patients with locally advanced tumors, surgical resection is the current standard. The extent of the lymphadenectomy depends on the localization of the tumor, analogous to the choice of surgical technique. For adequate tumor staging and achievement of pN0 status, seven lymph nodes without tumor metastases are necessary by definition but the current guidelines recommend 20 lymph nodes as a benchmark in an expert consensus. Despite the importance of the lymph node status for the prognosis of the patient and the already standardized use of targeted imaging of sentinel lymph nodes in other oncological disciplines, there is neither a validated method nor sufficient evidence for the benefit of lymph node mapping in esophageal cancer. The discussion about the prognostic advantage of lymphadenectomy is particularly interesting in T1 early stage cancer. Due to the technical advances of interventional endoscopy in recent years, organ preservation using endoscopic submucosal dissection (ESD) or endoscopic mucosal resection (EMR) has not only become possible but also safe to carry out and thus established as the standard with better functional results; however, if one or more risk factors are present, endoscopic ablation is no longer defined as curative and should be supplemented by further treatment, usually non-organ-preserving resection. The step from organ-preserving interventional treatment with a low complication rate to a surgical procedure with significant mortality and morbidity as well as functional limitations seems immense and requires optimization, especially in view of the technical developments of surgery in recent years. This can either aim to identify the risk of lymph node metastases more precisely or to minimize the morbidity/mortality and functional limitations of additive treatment procedures. Approaches to this are currently the subject of research and have already been safely applied in individual pilot projects.

Prognostic role of lymph node micrometastasis in pN0 esophageal cancer: A meta-analysis

BACKGROUND

To further identify the association between the lymph node micrometastasis (LNM) and long-term survival among pN0 esophageal cancer patients receiving the surgery.

METHODS

Several databases were searched for relevant studies up to June 22, 2023. The primary and secondary outcomes were separately overall survival (OS) and relapse-free survival (RFS) and hazard ratios (HRs) with 95% confidence intervals (CIs) were combined. Subgroup analysis based on pathological type and source of HR was further performed. All statistical analyses were conducted by STATA 15.0 software.

RESULTS

A total of 20 studies involving 1830 pN0 patients were included in this meta-analysis. The pooled results demonstrated that the presence of LNM indicated significantly worse OS (HR = 2.19, 95% CI = 1.77-2.70, P < .001) and RFS (HR = 2.15, 95% CI = 1.65-2.80, P < .001). Besides, subgroup analysis for the OS and RFS stratified by the pathological type (squamous cell carcinoma vs mixed esophageal cancer) and source of HR (reported vs estimated) further identified the significant relationship of LNM with prognosis in surgical esophageal cancer.

CONCLUSION

The presence of LNM indicated significantly poorer long-term survival among operated pN0 esophageal cancer patients. LNM could serve as a novel and reliable prognostic indicator in surgical esophageal cancer.

Graphical modeling of causal factors associated with the postoperative survival of esophageal cancer subjects

PURPOSE

To clarify the causal relationship between factors contributing to the postoperative survival of patients with esophageal cancer.

METHODS

A cohort of 195 patients who underwent surgery for esophageal cancer between 2008 and 2021 was used in the study. All patients had preoperative chest computed tomography (CT) and positron emission tomography-CT (PET-CT) scans prior to receiving any treatment. From these images, high throughput and quantitative radiomic features, tumor features, and various body composition features were automatically extracted. Causal relationships among these image features, patient demographics, and other clinicopathological variables were analyzed and visualized using a novel score-based directed graph called "Grouped Greedy Equivalence Search" (GGES) while taking prior knowledge into consideration. After supplementing and screening the causal variables, the intervention do-calculus adjustment (IDA) scores were calculated to determine the degree of impact of each variable on survival. Based on this IDA score, a GGES prediction formula was generated. Ten-fold cross-validation was used to assess the performance of the models. The prediction results were evaluated using the R-Squared Score (R2 score).

RESULTS

The final causal graphical model was formed by two PET-based image variables, ten body composition variables, four pathological variables, four demographic variables, two tumor variables, and one radiological variable (Percentile 10). Intramuscular fat mass was found to have the most impact on overall survival month. Percentile 10 and overall TNM (T: tumor, N: nodes, M: metastasis) stage were identified as direct causes of overall survival (month). The GGES casual model outperformed GES in regression prediction (R2  = 0.251) (p < 0.05) and was able to avoid unreasonable causality that may contradict common sense.

CONCLUSION

The GGES causal model can provide a reliable and straightforward representation of the intricate causal relationships among the variables that impact the postoperative survival of patients with esophageal cancer.