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Aim: The prognosis for gastric cancer (GC) remains grim, underscoring the importance of accurate staging and treatment. Given the potential benefits of using lymph node ratio (LNR) for improved prognostication and treatment planning, it is critical to incorporate examined lymph nodes (ELN) count in an integrated GC staging system. Methods: Patients data from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2015 was utilized as training set. The Mantel-Cox survival test was used to calculate chi-square values for 40 LNR segments with a 0.025 interval, defining a novel LNR-based N (rN) classification based on the cutoff points. A revised AJCC (rAJCC) staging system was established by replacing the 8th AJCC N staging with a rN classification. The relationship between the ELN count and prognosis or positive lymph node detection was conducted by using multivariable models. The series of the odds ratios and hazard ratios were fitted with a locally weighted scatterplot smoothing (LOWESS) smoother, and the structural break points were determined by Chow test to clarify an optimal minimum ELN count. The integrated GC staging system incorporated both rAJCC system and the ideal ELN count. Discriminatory ability and prognostic homogeneity of the rAJCC and integrated staging system was compared with AJCC staging system in the SEER validation set (2016–2017), the Cancer Genome Atlas Program (TCGA) database, and the Third Affiliated Hospital of Sun Yat-sen University database. Results: The current study found that LNR and ELN count are both significantly associated with the prognosis of GC patients (HR = 0.98, p < 0.001 and HR = 2.51, p < 0.001). Four peaks of the chi-square value were identified as LNR cut-off points at 0.025, 0.175, 0.45 and 0.6 to define a novel rN stage. In comparison to the 8th AJCC staging system, the rAJCC staging system demonstrated significant prognostic advantages and discriminatory ability in the training set (5-Y OS AUC: 71.7 vs. 73.0; AIC: 57,290.7 vs. 57,054.9). The superiority of the rAJCC staging system was confirmed in all validation sets. Using a LOWESS smoother and Chow test, a threshold ELN count of 30 was determined to maximum improvement in the prognosis of node-negative patients without downgrading due to potential metastasis, while also maximizing the detection efficiency of at least one involved lymph node. The integrated staging system, combining the refined rAJCC classification with an optimized ELN count threshold, has demonstrated superior discriminatory performance compared to the standalone rAJCC or the traditional AJCC system. Conclusion: The development of a novel GC staging system, which integrated the LNR-based N classification and the minimum ELN count, has exhibited superior prognostic accuracy, holding promise as a valuable asset in the clinical management of GC. However, it is crucial to recognize the limitations from the retrospective database, which should be addressed in subsequent analyses. [ABSTRACT FROM AUTHOR]

Aim The prognosis for gastric cancer (GC) remains grim, underscoring the importance of accurate staging and treatment. Given the potential benefits of using lymph node ratio (LNR) for improved prognostication and treatment planning, it is critical to incorporate examined lymph nodes (ELN) count in an integrated GC staging system. Methods Patients data from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2015 was utilized as training set. The Mantel-Cox survival test was used to calculate chi-square values for 40 LNR segments with a 0.025 interval, defining a novel LNR-based N (rN) classification based on the cutoff points. A revised AJCC (rAJCC) staging system was established by replacing the 8th AJCC N staging with a rN classification. The relationship between the ELN count and prognosis or positive lymph node detection was conducted by using multivariable models. The series of the odds ratios and hazard ratios were fitted with a locally weighted scatterplot smoothing (LOWESS) smoother, and the structural break points were determined by Chow test to clarify an optimal minimum ELN count. The integrated GC staging system incorporated both rAJCC system and the ideal ELN count. Discriminatory ability and prognostic homogeneity of the rAJCC and integrated staging system was compared with AJCC staging system in the SEER validation set (2016–2017), the Cancer Genome Atlas Program (TCGA) database, and the Third Affiliated Hospital of Sun Yat-sen University database. Results The current study found that LNR and ELN count are both significantly associated with the prognosis of GC patients (HR = 0.98, p < 0.001 and HR = 2.51, p < 0.001). Four peaks of the chi-square value were identified as LNR cut-off points at 0.025, 0.175, 0.45 and 0.6 to define a novel rN stage. In comparison to the 8th AJCC staging system, the rAJCC staging system demonstrated significant prognostic advantages and discriminatory ability in the training set (5-Y OS AUC: 71.7 vs. 73.0; AIC: 57,290.7 vs. 57,054.9). The superiority of the rAJCC staging system was confirmed in all validation sets. Using a LOWESS smoother and Chow test, a threshold ELN count of 30 was determined to maximum improvement in the prognosis of node-negative patients without downgrading due to potential metastasis, while also maximizing the detection efficiency of at least one involved lymph node. The integrated staging system, combining the refined rAJCC classification with an optimized ELN count threshold, has demonstrated superior discriminatory performance compared to the standalone rAJCC or the traditional AJCC system. Conclusion The development of a novel GC staging system, which integrated the LNR-based N classification and the minimum ELN count, has exhibited superior prognostic accuracy, holding promise as a valuable asset in the clinical management of GC. However, it is crucial to recognize the limitations from the retrospective database, which should be addressed in subsequent analyses.

Abstract Background The role of tumor-draining lymph nodes in the progression of malignant tumors, including stage III colorectal cancer (CRC), is critical. However, the prognostic and predictive value of the number of examined lymph nodes (ELNs) are not fully understood. Methods This population-based study retrospectively analyzed data from 106,843 patients with stage III CRC who underwent surgical treatment and registered in three databases from 2004 to 2021. The Surveillance, Epidemiology, and End Results (SEER) cohort was divided using into training and test cohorts at a ratio of 3:2. We employed restricted cubic spline (RCS) curves to explore nonlinear relationships between overall survival (OS) and ELNs counts and performed Cox regression to evaluate hazard ratios across different ELNs count subtypes. Additional validation cohorts were utilized from the First Affiliated Hospital, Sun Yat-sen University and The Cancer Genome Atlas (TCGA) under the same criteria. Outcomes measured included OS, cancer-specific survival (CSS), and progression-free survival (PFS). Molecular analyses involved differential gene expression using the “limma” package and immune profiling through CIBERSORT. Tissue microarray slides and multiplex immunofluorescence (MIF) were used to assess protein expression and immune cell infiltration. Results Patients with higher ELNs counts (≥ 17) demonstrated significantly better long-term survival outcomes across all cohorts. Enhanced OS, CSS, and PFS were notably evident in the LN-ELN group compared to those with fewer ELNs. Cox regression models underscored the prognostic value of higher ELNs counts across different patient subgroups by age, sex, tumor differentiation, and TNM stages. Subtype analysis based on ELNs count revealed a marked survival benefit in patients treated with adjuvant chemotherapy in the medium and large ELNs counts (≥ 12), whereas those with fewer ELNs showed negligible benefits. RNA sequencing and MIF indicated elevated immune activation in the LN-ELN group, characterized by increased CD3+, CD4+, and CD8 + T cells within the tumor microenvironment. Conclusions The number of ELNs independently predicts survival and the immunological landscape at the tumor site in stage III CRC, underscoring its dual prognostic and predictive value.

Background: The role of tumor-draining lymph nodes in the progression of malignant tumors, including stage III colorectal cancer (CRC), is critical. However, the prognostic and predictive value of the number of examined lymph nodes (ELNs) are not fully understood. Methods: This population-based study retrospectively analyzed data from 106,843 patients with stage III CRC who underwent surgical treatment and registered in three databases from 2004 to 2021. The Surveillance, Epidemiology, and End Results (SEER) cohort was divided using into training and test cohorts at a ratio of 3:2. We employed restricted cubic spline (RCS) curves to explore nonlinear relationships between overall survival (OS) and ELNs counts and performed Cox regression to evaluate hazard ratios across different ELNs count subtypes. Additional validation cohorts were utilized from the First Affiliated Hospital, Sun Yat-sen University and The Cancer Genome Atlas (TCGA) under the same criteria. Outcomes measured included OS, cancer-specific survival (CSS), and progression-free survival (PFS). Molecular analyses involved differential gene expression using the "limma" package and immune profiling through CIBERSORT. Tissue microarray slides and multiplex immunofluorescence (MIF) were used to assess protein expression and immune cell infiltration. Results: Patients with higher ELNs counts (≥ 17) demonstrated significantly better long-term survival outcomes across all cohorts. Enhanced OS, CSS, and PFS were notably evident in the LN-ELN group compared to those with fewer ELNs. Cox regression models underscored the prognostic value of higher ELNs counts across different patient subgroups by age, sex, tumor differentiation, and TNM stages. Subtype analysis based on ELNs count revealed a marked survival benefit in patients treated with adjuvant chemotherapy in the medium and large ELNs counts (≥ 12), whereas those with fewer ELNs showed negligible benefits. RNA sequencing and MIF indicated elevated immune activation in the LN-ELN group, characterized by increased CD3+, CD4+, and CD8 + T cells within the tumor microenvironment. Conclusions: The number of ELNs independently predicts survival and the immunological landscape at the tumor site in stage III CRC, underscoring its dual prognostic and predictive value. [ABSTRACT FROM AUTHOR]

Introduction: In early-stage epithelial ovarian cancer (EOC), how to perform lymphadenectomy to avoid stage migration and achieve reliable targeted excision has not been explored in depth. This study comprehensively considered the stage migration and survival to determine appropriate numbers of examined lymph node (ELN) for early-stage EOC and high-grade serous ovarian cancer (HGSOC). Methods: From the Surveillance, Epidemiology, and End Results database, we obtained 10372 EOC cases with stage T1M0 and ELN = 2, including 2849 HGSOC cases. Generalized linear models with multivariable adjustment were used to analyze associations between ELN numbers and lymph node stage migration, survival and positive lymph node (PLN). LOESS regression characterized dynamic trends of above associations followed by Chow test to determine structural breakpoints of ELN numbers. Survival curves were plotted using Kaplan-Meier method. Results: More ELNs were associated with more node-positive diseases, more PLNs and better prognosis. ELN structural breakpoints were different in subgroups of early-stage EOC, which for node stage migration or PLN were more than those for improving outcomes. The meaning of ELN structural breakpoint varied with its location and the morphology of LOESS curve. To avoid stage migration, the optimal ELN for early-stage EOC was 29 and the minimal ELN for HGSOC was 24. For better survival, appropriate ELN number were 13 and 8 respectively. More ELNs explained better prognosis only at a certain range. Discussion: Neither too many nor too few numbers of ELN were ideal for earlystage EOC and HGSOC. Excision with appropriate numbers of lymph node draining the affected ovary may be more reasonable than traditional sentinel lymph node resection and systematic lymphadenectomy. [ABSTRACT FROM AUTHOR]

Abstract Background Individuals with pN3 gastric cancer (GC) account for a large proportion of pN + GC, and exhibit poor survival outcomes. The pN3 stage is defined based upon the number of metastatic lymph nodes (mLNs), but the subclassification of pN3 patients based upon the number of examined LNs (eLNs) is rarely performed. Methods In total, 2894 pTxN3M0 GC patients in the Surveillance, Epidemiology, and End Results database that had undergone surgery from 2000 to 2016 were selected for analysis. The X-tile software was used to select the optimal cutoff values. Cox proportional regression analyses were used to evaluated hazard ratios corresponding to the risk of death. Selection bias was minimized via propensity score matching (PSM). Results As the number of eLNs rose, the risk of death for patients trended downwards. Survival analyses indicated that patients with ≤ 31 eLNs exhibited significantly poorer survival outcomes as compared to patients with > 31 eLNs (5-year OS: 18.4% vs. 24.7%), and this result remained significant when analyzing 857 pairs of patients following PSM analysis. Significant differences in prognosis were additionally observed when comparing pN3a and pN3b patients with ≤ 31 or > 31 eLNs under pT3/4a stage. For pT4b stage, pN3a patients with > 31 eLNs also exhibited a better prognosis than other patients. The novel TNM staging system designed exhibited excellent utility as a tool for the prognostic evaluation of this GC patient population. Conclusions These results suggest that in pN3 GC, a minimum of 32 LNs should be examined. The novel TNM staging system for pN3 patients described herein, which was developed based upon the number of eLNs, may thus be of value in clinical settings.

Background: Individuals with pN3 gastric cancer (GC) account for a large proportion of pN + GC, and exhibit poor survival outcomes. The pN3 stage is defined based upon the number of metastatic lymph nodes (mLNs), but the subclassification of pN3 patients based upon the number of examined LNs (eLNs) is rarely performed.Methods: In total, 2894 pTxN3M0 GC patients in the Surveillance, Epidemiology, and End Results database that had undergone surgery from 2000 to 2016 were selected for analysis. The X-tile software was used to select the optimal cutoff values. Cox proportional regression analyses were used to evaluated hazard ratios corresponding to the risk of death. Selection bias was minimized via propensity score matching (PSM).Results: As the number of eLNs rose, the risk of death for patients trended downwards. Survival analyses indicated that patients with ≤ 31 eLNs exhibited significantly poorer survival outcomes as compared to patients with > 31 eLNs (5-year OS: 18.4% vs. 24.7%), and this result remained significant when analyzing 857 pairs of patients following PSM analysis. Significant differences in prognosis were additionally observed when comparing pN3a and pN3b patients with ≤ 31 or > 31 eLNs under pT3/4a stage. For pT4b stage, pN3a patients with > 31 eLNs also exhibited a better prognosis than other patients. The novel TNM staging system designed exhibited excellent utility as a tool for the prognostic evaluation of this GC patient population.Conclusions: These results suggest that in pN3 GC, a minimum of 32 LNs should be examined. The novel TNM staging system for pN3 patients described herein, which was developed based upon the number of eLNs, may thus be of value in clinical settings. [ABSTRACT FROM AUTHOR]

Background: We aimed to investigate the association between optimal examined lymph node (ELNs) and overall survival to determine the optimal cutoff point. Methods: Cox models and locally weighted scatterplot smoothing were used to fit hazard ratios and explore an optimal cutoff point based on the Chow test. Results: Overall survival increased significantly with the corresponding increase in the number of ELNs after adjusting for covariates. In Chow's test, the optimal cutoff point for node-negative colon cancer was 15, which was validated in both cohorts after controlling for confounders (Surveillance, Epidemiology, and End Results database: hazard ratio: 0.701, p < 0.001; single-center: HR: 0.563; p = 0.031). Conclusions: We conservatively suggest that the optimal number of ELNs for prognostic stratification is 15 in node-negative colon cancer. [ABSTRACT FROM AUTHOR]

ObjectiveThis study aimed to analyze the relationship between the number of examined lymph nodes (ELNs) at the N1 station and the postoperative clinicopathological features and prognosis of patients with pT1-3N0M0 non-small cell lung cancer (NSCLC).MethodsThe cut-off value of the number of ELNs at the N1 station was obtained using X-tile software analysis. Kaplan-Meier survival curve analysis and the Cox proportional hazard model were used to study the impact of the number of ELNs at the N1 station on the prognosis of postoperative patients with pT1-3N0M0 NSCLC.ResultsThe median survival time and 1-, 3- and 5-year survival rates of 0 ELNs at the N1 station were 28.0 months and 74.8%, 45.4%, and 21.2%, respectively. The median survival time and 1-, 3-, and 5-year survival rates of 1–4 ELNs at the N1 station were 45.0 months and 85.5%, 55.4%, and 39.1%, respectively. In the group with ≥ 5 ELNs at the N1 station, the median survival time and the 1-, 3- and 5-year survival rates were 59.0 months and 94.0%, 62.7%, and 48.2%, respectively. Both univariate and multivariate Cox regression analyses showed that the number of ELNs at the N1 station, T stage and operation type were independent factors affecting the prognosis of patients with pT1-3N0M0 NSCLC.ConclusionIncreasing the number of ELNs at the N1 station is positively correlated with the long-term survival rate of patients with T1-3N0M0 NSCLC. At least 5 LNs at the N1 station should be examined in pathological examination.

Purpose The relationship between examined lymph nodes (ELN) and survival has been confirmed in several single early-stage malignancies. We studied the association between the ELN count and the long-term survival of T1-2N0M0 double primary non-small cell lung cancer (DP-NSCLC) patients after surgery, based on the Surveillance, Epidemiology and End Results (SEER) database. Methods A total of 948 patients were identified and their independent prognostic factors were analyzed. These factors included the ELN count, which related to overall survival (OS) and the cancer-specific survival (CSS) of synchronous (n = 426) and metachronous (n = 522) T1-2N0M0 DP-NSCLC patients after surgery. Results X-tile analysis indicated that the cutoff value for the sum of ELNs was 22 for both OS and CSS in the synchronous DP-NSCLC group. Patients with a sum of ELNs >22 were statistically more likely to survive than those with ≤22 ELNs. X-tile analysis revealed that the ELN count of the second lesion was related to both OS and CSS in the metachronous DP-NSCLC group. The optimal cutoff value was nine. These results were confirmed using univariate and multivariate Cox regression analyses. Conclusion Our findings indicate that ELN count was highly correlated with the long-term survival of T1-2N0M0 double primary NSCLC patients after surgery.

Objective: This study aimed to analyze the relationship between the number of examined lymph nodes (ELNs) at the N1 station and the postoperative clinicopathological features and prognosis of patients with pT1-3N0M0 non-small cell lung cancer (NSCLC). Methods: The cut-off value of the number of ELNs at the N1 station was obtained using X-tile software analysis. Kaplan-Meier survival curve analysis and the Cox proportional hazard model were used to study the impact of the number of ELNs at the N1 station on the prognosis of postoperative patients with pT1-3N0M0 NSCLC. Results: The median survival time and 1-, 3- and 5-year survival rates of 0 ELNs at the N1 station were 28.0 months and 74.8%, 45.4%, and 21.2%, respectively. The median survival time and 1-, 3-, and 5-year survival rates of 1–4 ELNs at the N1 station were 45.0 months and 85.5%, 55.4%, and 39.1%, respectively. In the group with ≥ 5 ELNs at the N1 station, the median survival time and the 1-, 3- and 5-year survival rates were 59.0 months and 94.0%, 62.7%, and 48.2%, respectively. Both univariate and multivariate Cox regression analyses showed that the number of ELNs at the N1 station, T stage and operation type were independent factors affecting the prognosis of patients with pT1-3N0M0 NSCLC. Conclusion: Increasing the number of ELNs at the N1 station is positively correlated with the long-term survival rate of patients with T1-3N0M0 NSCLC. At least 5 LNs at the N1 station should be examined in pathological examination. [ABSTRACT FROM AUTHOR]

Introduction: In early-stage epithelial ovarian cancer (EOC), how to perform lymphadenectomy to avoid stage migration and achieve reliable targeted excision has not been explored in depth. This study comprehensively considered the stage migration and survival to determine appropriate numbers of examined lymph node (ELN) for early-stage EOC and high-grade serous ovarian cancer (HGSOC)., Methods: From the Surveillance, Epidemiology, and End Results database, we obtained 10372 EOC cases with stage T1M0 and ELN ≥ 2, including 2849 HGSOC cases. Generalized linear models with multivariable adjustment were used to analyze associations between ELN numbers and lymph node stage migration, survival and positive lymph node (PLN). LOESS regression characterized dynamic trends of above associations followed by Chow test to determine structural breakpoints of ELN numbers. Survival curves were plotted using Kaplan-Meier method., Results: More ELNs were associated with more node-positive diseases, more PLNs and better prognosis. ELN structural breakpoints were different in subgroups of early-stage EOC, which for node stage migration or PLN were more than those for improving outcomes. The meaning of ELN structural breakpoint varied with its location and the morphology of LOESS curve. To avoid stage migration, the optimal ELN for early-stage EOC was 29 and the minimal ELN for HGSOC was 24. For better survival, appropriate ELN number were 13 and 8 respectively. More ELNs explained better prognosis only at a certain range., Discussion: Neither too many nor too few numbers of ELN were ideal for early-stage EOC and HGSOC. Excision with appropriate numbers of lymph node draining the affected ovary may be more reasonable than traditional sentinel lymph node resection and systematic lymphadenectomy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Li, Ding, Zheng, Xu, Li, Zhu, Zhang, Ma, Zhang, Zhong, Liang, Han, Zhang, He and Li.)

There has been a long-standing controversy regarding the number of lymph nodes (LNs) examined intraoperatively for accurate lymphatic staging and significantly better survival of patients with pancreatic ductal adenocarcinoma (PDAC), and no consensus has been reached for the elderly with the age of over 75 years. Given these, the present study aims to investigate the appropriate number of examined lymph nodes (ELNs) for elderly patients mentioned above. In this study, population-based data on 20,125 patients in 2000 to 2019 from the Surveillance, Epidemiology, and End Results database were reviewed retrospectively. The eighth edition staging system of the American Joint Committee on Cancer (AJCC) was applied. Propensity score matching (PSM) was performed to reduce the effects of multiple biases. By using binomial probability law and maximally selected rank statistics, the minimum number of ELN (MNELN) for accurate nodal involvement assessment and optimal ELN number for significantly better survival were calculated, respectively. In addition, Kaplan-Meier curves and Cox proportional hazard regression models were constructed for further survival analysis. As a result, 6623 patients were enrolled in total in the study. Elderly patients had fewer lymph node metastases and a smaller lymph node ratio (LNR) (all P <0.05). However, poorer overall survival (OS) and cancer-specific survival (CSS) of elderly patients were observed in each pN stage (all P <0.05), except for CSS in N2. The proportions of N2 and N0 stages increased and decreased respectively with increasing number of ELN significantly. MNELN for accurate nodal assessment was 19 according to binomial probability law, and the optimal ELN number for significantly better survival was 17. Additionally, the number of ELN (<17 or ≥17) was also considered a strong prognostic predictor for elderly PDAC patients (≥75 years) in the Cox proportional hazard regression model (Overall survival: hazard ratio [HR]=0.74, 95% confidence interval [CI]: 0.65-0.83, P <0.001; Cancer-specific survival: HR=0.75, 95% CI: 0.66-0.85, P <0.001). In conclusion, extended lymphadenectomy is suitable for elderly PDAC patients undergoing curative-intent surgery owing to an accurate assessment of nodal status and improved long-term prognosis. However, a random, prospective clinical trial is warranted before the recommendation of extended lymphadenectomy for the elderly., Competing Interests: None., (AJCR Copyright © 2023.)

The minimum number of lymph nodes to be examined during pancreaticoduodenectomy (PD) for patients with ampullary adenocarcinoma (AC) is still debatable due to limited clinical data. Therefore, here we explored the relationship between the number of examined lymph node (ELN) and the current N staging (American Joint Committee on Cancer staging system, AJCC, 8 edition) after PD for AC as well as determined the minimum number of examined lymph nodes (MNELN) to ensure the accurate detection of nodal involvement. Patients underwent PD for AC in the National Cancer Center cohort of China (NCC cohort of China) from 1998 to 2020 and in the Surveillance, Epidemiology, and End Results database (SEER database) from 2010 to 2018 were retrospectively reviewed, and a total of 452 eligible patients were included in this study. The MNELN was evaluated by binomial probability law and best survival separation methods. Furthermore, the cut-off value of MNELN was validated in the NCC cohort of China using Least Absolute Shrinkage and Selection Operator (LASSO) regression. Our analysis indicated that the median number of ELN was 14, and the number of ELN was positively correlated with N stage. The MNELN was 16, whereas the best survival separation of ELN was 38 in node-positive patients and 3 in node-negative patients. In the validation cohort, the number of 16 ELNs was identified as a predictive variable for lymph node metastasis with nonzero coefficients in the LASSO-logistic regression model. Together, we concluded that a greater number of ELN was associated with more accurate nodal status assessment in PD for AC patients. A minimum of 16 lymph nodes were required to during PD in AC patients., Competing Interests: None., (AJCR Copyright © 2023.)

Reply to the letter to the editor: 'AJCC 8th edition staging system for pancreatic ductal adenocarcinoma: A controversial step forward? Although only a few patients had pT4 disease, there was a significant difference in the survival time (16.9 months for patients with stage IIIA disease vs. 11.2 months for patients with stage IIIB disease; p < 0.01). Another study that analyzed 68 patients with pT4 disease and 41 patients with pN2 disease also showed significant differences (14.2 months for N2 patients and 12.0 months for T4 patients; p = 0.034) [[4]]. [Extracted from the article]

Purpose: The relationship between examined lymph nodes (ELN) and survival has been confirmed in several single early-stage malignancies. We studied the association between the ELN count and the long-term survival of T1-2N0M0 double primary non-small cell lung cancer (DP-NSCLC) patients after surgery, based on the Surveillance, Epidemiology and End Results (SEER) database., Methods: A total of 948 patients were identified and their independent prognostic factors were analyzed. These factors included the ELN count, which related to overall survival (OS) and the cancer-specific survival (CSS) of synchronous ( n = 426) and metachronous ( n = 522) T1-2N0M0 DP-NSCLC patients after surgery., Results: X-tile analysis indicated that the cutoff value for the sum of ELNs was 22 for both OS and CSS in the synchronous DP-NSCLC group. Patients with a sum of ELNs >22 were statistically more likely to survive than those with ≤22 ELNs. X-tile analysis revealed that the ELN count of the second lesion was related to both OS and CSS in the metachronous DP-NSCLC group. The optimal cutoff value was nine. These results were confirmed using univariate and multivariate Cox regression analyses., Conclusion: Our findings indicate that ELN count was highly correlated with the long-term survival of T1-2N0M0 double primary NSCLC patients after surgery., Competing Interests: The authors declare that they have no competing interests., (© 2020 Jiang et al.)