Adaptive river flow measurement method based on spatiotemporal image velocimetry and optical flow.

This paper proposes an adaptive river discharge measurement method based on spatiotemporal image velocimetry (STIV) and optical flow to solve the problem of blurred texture features and limited measurement accuracy under complex natural environmental conditions. Optical flow tracking generates spatiotemporal images by following the flow mainstream direction of rivers with both regular and irregular natural banks. A texture similarity function filtering method effectively enhances spatiotemporal texture features. The proposed method is applied to a natural river, with measurement results from a propeller-type current meter used as truth values. It is evaluated and compared with three other methods regarding measurement accuracy, error, and other evaluation indices. The results demonstrate that the method significantly improves spatiotemporal image quality. Its estimation outcomes perform better across all evaluation metrics, enhancing the adaptability and accuracy of the flow measurement method.

Combined Use of Tumor Markers in Gastric Cancer: A Novel Method with Promising Prognostic Accuracy and Practicality.

BACKGROUND: The effect of a single tumor marker on the prognosis of gastric cancer patients is not ideal. This study explored a novel prognostic assessment method for gastric cancer (GC) patients using a combination of three important tumor markers (CEA, CA72-4, and CA19-9). METHOD: Data from 1966 GC patients who underwent curative gastrectomy at Sun Yat-Sen University Cancer Center (Guangzhou, China) were included. Hazard ratios (HR) for all factors for overall survival (OS) were analyzed by Cox regression. A nomogram and calibration curve were used to establish the survival prediction model. The prediction accuracy was evaluated with the concordance index (C-index). RESULTS: All patients were divided into four groups (C0-C3) according to the number of elevated tumor markers. The 5-year OS rates of the patients in preoperative groups C0-C3 were 83.8% (81.3-86.4%), 72.8% (68.5-77.4%), 58.9% (50.4-68.9%), and 18.5% (4.0-33.0%), respectively, and those in postoperative groups C0-C3 were 82.1% (79.4-84.8%), 76.1% (72.2-80.3%), 57.6% (48.4-68.5%), and 16.8% (5.1-28.5%), respectively, with significant differences between each C0-C3 subgroup in both preoperative and postoperative cohorts. Multivariate analysis showed that preoperative (HR: 6.001, 95% CI: 3.523-10.221) and postoperative (HR: 8.149, 95% CI: 4.962-13.528) elevated tumor markers were independent risk factors for GC patients. The C-index for the combined use of tumor markers was 0.65-0.66, which was higher than that for using a single tumor marker (0.53-0.56). CONCLUSION: The combined use of tumor markers significantly improved the prognostic value compared with using a single tumor marker. The survival prediction model including the combined tumor markers was accurate and effective.

Adjuvant Chemotherapy for Patients with Adenocarcinoma of the Esophagogastric Junction: A Retrospective, Multicenter, Observational Study.

BACKGROUND: Although the incidence of adenocarcinoma of the esophagogastric junction (AEG) has been increasing since the past decade, the proportion of AEG cases in two previous clinical trials (ACTS-GC and CLASSIC) that investigated the efficacy of adjuvant chemotherapy was relatively small. Therefore, whether AEG patients can benefit from adjuvant chemotherapy remains unclear. METHODS: Patients who were diagnosed with pathological stage II/III, Siewert II/III AEG, and underwent curative surgery at three high-volume institutions were assessed. Clinical outcomes were analyzed by using Kaplan-Meier curves, log-rank test, and Cox regression model. Propensity score matching (PSM) was used to reduce the selection bias. RESULTS: A total of 927 patients were included (the chemotherapy group: 696 patients; the surgery-only group: 231 patients). The median follow-up was 39.0 months. The 5-year overall survival was 63.1% (95% confidence interval [CI]: 59.0-67.6%) for the chemotherapy group and 50.2% in the surgery-only group (hazard ratio [HR] = 0.69, 95% CI: 0.54-0.88; p = 0.003). The 5-year, disease-free survival was 35.4% for the chemotherapy group and 16.6% for the surgery-only group (HR = 0.66, 95% CI: 0.53-0.83; p < 0.001). After PSM, the survival benefit of adjuvant chemotherapy for AEG was maintained. Multivariate analysis for overall survival and disease-free survival further demonstrated the survival benefit of adjuvant chemotherapy, with HRs of 0.63 (p < 0.001) and 0.52 (p < 0.001), respectively. CONCLUSIONS: Postoperative adjuvant chemotherapy was associated with improved overall survival and disease-free survival in patients with operable stage II or III AEG after D2 gastrectomy.

Indications for Adjuvant Chemotherapy in Stage II Gastric Cancer After D2 Gastrectomy-A Chinese Multicenter Study.

BACKGROUND: The benefit of adjuvant chemotherapy (AC) for patients with stage II gastric cancer remains controversial. This study aimed to explore the indications for adjuvant chemotherapy in patients with stage II gastric cancer by constructing an individual prediction model. PATIENTS AND METHODS: In this Chinese multicenter study, a total of 1012 patients with stage II gastric cancer after D2 radical gastrectomy were retrospectively analyzed. All patients were randomly assigned to a training cohort (n = 674) or a validation cohort (n = 338). A nomogram was constructed according to the training cohort. Concordance index (C-index), the area under the receiver operating characteristic (ROC) curves (AUC), calibration curves, and decision curve analysis (DCA) were applied to evaluate the performance of the nomogram. ROC curves and stratified survival were used to determine the patients' cutoff score for a benefit from adjuvant chemotherapy. An additional 338 patients were used as a validation cohort to validate the feasibility of using this nomogram to guide individualized therapy for patients with stage II gastric cancer. RESULTS: Univariate and multivariate analyses illustrated that age, sex, tumor location, size, carcinoembryonic antigen (CEA), hemoglobin (HB), and T stage were independent prognostic factors for overall survival (OS), and they were used to establish a nomogram. The cutoff value was determined by ROC curve analysis, and patients were divided into a high-risk group (< 239 points) and a low-risk group (≥ 239 points). There was no significant difference in the OS of low-risk patients in either the training cohort or the validation cohort. However, the OS of high-risk patients in the AC group was better than that of patients in the surgery-only group. CONCLUSIONS: This prediction model can be applied to guide treatment of patients with stage II gastric cancer. High-risk patients (< 239 points) are likely to benefit from AC after D2 radical gastrectomy.

Survival analysis of stage II gastric cancer patients after D2 gastrectomy: a Chinese people-based research.

OBJECTIVE: The benefit of adjuvant chemotherapy is still controversial for stage II gastric cancer patients. This study aims to identify prognostic factors to guide individualized treatment for stage II gastric cancer patients. METHODS: We retrospectively reviewed 1121 stage II gastric cancer patients who underwent D2 radical gastrectomy from 2007 to 2017 in the Sixth Affiliated Hospital of Sun Yat-sen University, FuJian Medical School Affiliated Union Hospital and Sun Yat-sen University Cancer Center. Propensity score matching was used to ensure that the baseline data were balanced between the adjuvant chemotherapy group and surgery-only group. Kaplan-Meier survival and multivariate Cox regression analyses were carried out to identify independent prognostic factors. RESULTS: In univariate analysis, after propensity score matching, age, tumor location, tumor size, CEA, T stage and N stage were associated with overall survival (OS). Multivariate analysis illustrated that age ≥ 60 years old, linitis plastica and T4 were independent risk factors for OS, but lower location and adjuvant chemotherapy were protective factors. CONCLUSION: Stage II gastric cancer patients with adverse prognostic factors (age ≥ 60, linitis plastica and T4) have poor prognosis. Adjuvant chemotherapy may be more beneficial for these patients.

Surgical Outcome and Long-Term Survival of Conversion Surgery for Advanced Gastric Cancer.

BACKGROUND: The present study aims to report the surgical outcome and long-term survival of conversion surgery and clarify its role in advanced gastric cancer. PATIENTS AND METHODS: A total of 95 primary advanced gastric adenocarcinoma patients who underwent systemic chemotherapy and conversion surgery were reviewed retrospectively. The survival of conversion surgery was analyzed by Cox regression and the Kaplan-Meier method. Surgical outcomes were analyzed according to the Clavien-Dindo classification. RESULTS: The median survival time (MST) of the 95 patients was 26.8 months, and the postoperative MST was 19.3 months. The MSTs of the patients in categories 1, 2, 3, and 4 were 28.8, 25.5, 43.6, and 11.3 months, respectively. The MSTs of the patients who underwent R0 resection (47 cases) and R1/2 resection (48 cases) were 49.3 months and 21.9 months, respectively. The MST of patients treated with total gastrectomy was shorter (21.9 months) than that of patients who underwent proximal (55.0 months) or distal (46.3 months) gastrectomy. Patients who received more than 6 cycles of induction chemotherapy had a longer MST than patients who received 3-5 cycles or 1-2 cycles (MST: 55.0 months versus 21.1 months versus 21.7 months). The incident postoperative complications and postoperative mortality rates were 10.5% and 1.1%, respectively. CONCLUSIONS: Advanced gastric cancer patients may obtain a survival benefit from conversion surgery, except category 4. Performing a sufficient number of cycles of induction chemotherapy (usually ≥ 6 cycles) is recommended. Surgical oncologists should perform R0 resection and avoid total gastrectomy.

Disease-free survival as a surrogate endpoint for overall survival in adjuvant trials of pancreatic cancer: a meta-analysis of 20 randomized controlled trials.

BACKGROUND: We aimed to assess whether disease-free survival (DFS) could serve as a reliable surrogate endpoint for overall survival (OS) in adjuvant trials of pancreatic cancer. METHODS: We systematically reviewed adjuvant randomized trials for non-metastatic pancreatic cancer after curative resection that reported a hazard ratio (HR) for DFS and OS. We assessed the correlation between treatment effect (HR) on DFS and OS, weighted by sample size or precision of hazard ratio estimate, assuming fixed and random effects, and calculated the surrogate threshold effect (STE). We also performed sensitivity analyses and a leave-one-out cross validation approach to evaluate the robustness of our findings. RESULTS: After screening 450 relevant articles, we identified a total of 20 qualifying trails comprising 5170 patients for quantitative analysis. We noted a strong correlation between the treatment effects for DFS and OS, with coefficient of determination of 0.82 in the random effect model, 0.82 in the fixed effect model, and 0.80 in the sample size weighting; the robustness of this finding was further verified by the leave-one-out cross-validation approach. Sensitivity analyses with restriction to phase 3 trials, large trials, trials with mature follow-up periods, and trials with adjuvant therapy versus adjuvant therapy strengthened the correlation (0.75 to 0.88) between DFS and OS. The STE was 0.96 for DFS. CONCLUSIONS: Therefore, DFS could be regarded as a surrogate endpoint for OS in adjuvant trials of pancreatic cancer. In future similar adjuvant trials, a hazard ratio for DFS of 0.96 or less would predict a treatment impact on OS.

Analysis and external validation of a nomogram to predict peritoneal dissemination in gastric cancer.

OBJECTIVE: Peritoneal dissemination is difficult to diagnose by conventional imaging technologies. We aimed to construct a nomogram to predict peritoneal dissemination in gastric cancer (GC) patients. METHODS: We retrospectively analyzed 1,112 GC patients in Sun Yat-sen University Cancer Center between 2001 and 2010 as the development set and 474 patients from The Sixth Affiliated Hospital, Sun Yat-sen University between 2010 and 2016 as the validation set. The clinicopathological variables associated with gastric cancer with peritoneal dissemination (GCPD) were analyzed. We used logistic regression analysis to identify independent risk factors for peritoneal dissemination. Then, we constructed a nomogram for the prediction of GCPD and defined its predictive value with a receiver operating characteristic (ROC) curve. External validation was performed to validate the applicability of the nomogram. RESULTS: In total, 250 patients were histologically identified as having peritoneal dissemination. Logistic regression analysis demonstrated that age, sex, tumor location, tumor size, signet-ring cell carcinoma (SRCC), T stage, N stage and Borrmann classification IV (Borrmann IV) were independent risk factors for peritoneal dissemination. We constructed a nomogram consisting of these eight factors to predict GCPD and found an optimistic predictive capability, with a C-index of 0.791, an area under the curve (AUC) of 0.791, and a 95% confidence interval (95% CI) of 0.762-0.820. The results found in the external validation set were also promising. CONCLUSIONS: We constructed a highly sensitive nomogram that can assist clinicians in the early diagnosis of GCPD and serve as a reference for optimizing clinical management strategies.

Risk-stratification model to select conversion surgery for advanced gastric cancer patients.

OBJECTIVE: Conversion surgery is a surgery with a purpose of R0 resection in primary advanced gastric cancer (GC) that responded well to systemic chemotherapy. This study aimed to explore the efficacy of conversion surgery for advanced GC. METHODS: A total of 618 advanced GC patients receiving systemic chemotherapy were stratified into low-, moderate- and high-risk groups based on a nomogram-predicted probability of overall survival. The survival of conversion surgery and chemotherapy alone groups was compared using the log-rank test and Cox regression analysis after propensity score matching (PSM). RESULTS: A nomogram with good discrimination (concordance index: 0.65) and accurate calibration was constructed. After PSM, the median survival time (MST) of conversion surgery was 26.80 months, compared with 16.60 months of chemotherapy alone (P<0.001). Conversion surgery was associated with a longer MST for patients in the low-risk group (30.40 monthsvs. 20.90 months, P=0.013), whereas it was not associated with prolonged survival in the moderate- and high-risk groups (P=0.221 and P=0.131, respectively). CONCLUSIONS: Conversion surgery was associated with longer survival, especially for low-risk population.

Preoperative controlling nutritional status (CONUT) score as a predictor of long-term outcome after curative resection followed by adjuvant chemotherapy in stage II-III gastric Cancer.

BACKGROUND: The prognostic value of preoperative controlling nutritional status (CONUT) has been reported in many malignancies. In present study, we aimed to clarify the prognostic impact of CONUT in gastric cancer (GC) receiving curative resection and adjuvant chemotherapy. METHODS: We retrospectively reviewed 697 consecutive patients undergoing curative surgery followed by adjuvant chemotherapy for Stage II-III GC between November 2000 and September 2012. Patients were classified into high (≥3) and low (≤2) CONUT groups according to the receiver operating characteristic (ROC) analysis. RESULTS: Of the included patients, 217 (31.1%) belonged to the high CONUT group. The high CONUT group had a significantly lower 5-year cancer-specific survival (CSS) rate than the low CONUT group (39.3 vs. 55.5%, P < 0.001). High CONUT score was significantly associated with larger tumor size, more lymph node metastasis, and poorer nutritional status, including lower body mass index (BMI), higher prognostic nutritional index (PNI) and the presence of preoperative anemia (all P < 0.05). Multivariate analysis revealed that CONUT score was an independent prognostic factor (HR: 1.553; 95% CI: 1.080-2.232; P = 0.017). Of note, in the low PNI group, CONUT score still effectively stratified CSS (P = 0.016). Furthermore, the prognostic significance of CONUT score was also maintained when stratified by TNM stage (all P < 0.05). CONCLUSIONS: CONUT score is considered a useful nutritional marker for predicting prognosis in stage II-III GC patients undergoing curative resection and adjuvant chemotherapy, and may help to facilitate the planning of preoperative nutritional interventions.

The microRNA-423-3p-Bim Axis Promotes Cancer Progression and Activates Oncogenic Autophagy in Gastric Cancer.

Human serum microRNAs (miRNAs) have been shown to serve as disease fingerprints for predicting survival of cancer patients. However, the roles of specific miRNAs involved in gastric cancer (GC) are largely unknown. In this study, miRNA profiling was performed on sera obtained from six patients in good- and poor-survival groups. Expression of miR-423-3p was validated by quantitative RT-PCR in another 67 GC serum samples and paired normal and cancerous gastric tissues. Luciferase reporter assays were used to identify the target gene Bcl-2-interacting mediator of cell death (Bim). As a result, between the good-survival and poor-survival groups, the expression of nine serum miRNAs was altered more than two-fold. Among these, miR-423-3p was significantly increased in the poor-survival group, and its overexpression in GC tissues predicted poor survival in 119 patients with GC. miR-423-3p was found to promote cell proliferation, migration, and invasion in cell lines and animal models. Mechanistically, knockdown of the autophagy-related gene (Atg) 7 rescued the GC-promoting effect of miR-423-3p. In conclusion, miR-423-3p activates oncogenic and Beclin-1-dependent autophagy and promotes GC progression by reducing the expression of Bim. The newly identified miR-423-3p-Bim axis might be a potential therapeutic target in GC.

Bursectomy for advanced gastric cancer: an update meta-analysis.

BACKGROUND: The present meta-analysis was to explore the surgical and oncological outcomes of bursectomy for advanced gastric cancer (AGC). METHODS: Relevant studies that evaluated the role of bursectomy for AGC were comprehensively examined to perform a meta-analysis. The primary outcomes were overall survival (OS) and disease-free survival (DFS). The secondary outcomes were the number of harvested lymph nodes (LNs), operation time, operative bleeding, hospital stay, postoperative complication and mortality. RESULTS: A total of seven studies comprising 2633 cases (1176 cases in the bursectomy group and 1457 cases in the non-bursectomy group) were finally included. There was no significant difference in OS (HR 0.95, P = 0.647) and DFS (HR 0.99, P = 0.936) between the two groups. Even for patients with serosa-penetrating tumours, OS was comparable between the two groups (HR 0.87, P = 0.356). The operation time of the bursectomy group was longer (weighted mean difference, WMD 32.76 min, P = 0.002). No significant difference was found between the two groups in terms of the number of dissected LNs (WMD 5.86, P = 0.157), operative bleeding (WMD 66.99 ml, P = 0.192) and hospital stay (WMD - 0.15 days, P = 0.766). The overall postoperative complication (relative risk, RR 1.08, P = 0.421) and mortality (RR 0.44, P = 0.195) were similar between two groups. CONCLUSIONS: This meta-analysis indicated that bursectomy is time-consuming without increasing the number of harvested LNs. Although bursectomy can be safely performed without increasing complications and mortality, it does not prolong the OS and DFS of AGC patients, including patients with serosa-penetrating tumours. Therefore, bursectomy should not be recommended as a standard procedure for AGC.

A nomogram to predict prognosis for gastric cancer with peritoneal dissemination.

OBJECTIVE: To identify independent prognostic factors to be included in a nomogram to predict the prognosis of gastric cancer patients with peritoneal dissemination. METHODS: This is a retrospective study on 684 patients with a histological diagnosis of gastric cancer with peritoneal dissemination from the Sun Yat-sen University Cancer Center as the development set, and 62 gastric cancer patients from the Sixth Affiliated Hospital of Sun Yat-sen University as the validation group. Chi-square test and Cox regression analysis were used to compare the clinicopathological variables and the prognosis of gastric cancer patients with peritoneal dissemination. The Harrell's concordance index (C-index) and calibration curve were determined for comparisons of predictive ability of the nomogram. RESULTS: Univariate and multivariate analyses showed that serum carcinoembryonic antigen (CEA) level (P=0.032), ascites grading (P=0.008), presence of extraperitoneal metastasis (P<0.001), seeding status (P=0.016) and performance status (P=0.009) were independent prognostic factors for gastric cancer patients with peritoneal dissemination in the development set. The nomogram model was constructed using these five factors. Internal validation showed that the C-index of the model was 0.641. For the external validation, the C-index of this model was 0.709. CONCLUSIONS: We developed and validated a nomogram to predict the prognosis for gastric cancer patients with peritoneal dissemination. This nomogram may play an important clinical role in guiding palliative therapy for these types of patients, although it may need more data for optimization.

Body mass index (BMI) may be a prognostic factor for gastric cancer with peritoneal dissemination.

BACKGROUND: The aim of this study is to investigate whether body mass index (BMI) is a prognostic factor in gastric cancer patients with peritoneal dissemination. METHODS: This is a retrospective study consisting of 518 patients with a histological diagnosis of gastric cancer with peritoneal dissemination seen at the Sixth Affiliated Hospital of Sun Yat-Sen University and Sun Yat-sen University Cancer Center between January 2010 and April 2014. Patients were followed until December 2015. Chi-square test and Kaplan-Meier survival analysis were used to compare the clinicopathological variables and prognosis. RESULTS: Univariate analyses showed that significant prognostic factors included palliative gastrectomy (p < 0.001), tumor size (p < 0.001), tumor location (p = 0.011), peritoneal seeding grade (p < 0.001), ascites (p = 0.001), serum CEA level (p = 0.002), serum CA19-9 level (p = 0.033), palliative chemotherapy (p < 0.001), and BMI group (p < 0.001). For patients with palliative chemotherapy, univariate analysis revealed that palliative gastrectomy (p < 0.001), tumor size (p = 0.002), tumor location (p = 0.024), peritoneal seeding grade (p = 0.008), serum CEA level (p = 0.041), and BMI group (p < 0.001). Multivariate analysis revealed that BMI was an independent prognostic factor in gastric cancer patients with peritoneal dissemination, especially in patients who received palliative chemotherapy. CONCLUSIONS: BMI is a prognostic factor for patients who have gastric cancer with peritoneal dissemination, especially in those who received palliative chemotherapy.

Endoscopic ultrasonography compared with multidetector computed tomography for the preoperative staging of gastric cancer: a meta-analysis.

BACKGROUND: The current study sought to perform a meta-analysis to compare the preoperative staging of endoscopic ultrasonography (EUS) and multidetector computed tomography (MDCT) in gastric carcinoma. METHODS: Articles published between January 1, 2000, and April 1, 2016, that compared EUS with MDCT were included, and data were presented as 2 × 2 tables. The sensitivities, specificities and summary receiver operating characteristic (ROC) curves for T and N staging were calculated using a bivariate mixed effects model. Data were weighted by generic variance and then pooled by random-effects modeling. RESULTS: Eight studies comprising 1736 patients were included in this meta-analysis. For T1 staging, the sensitivity value for EUS (82%) was significantly higher than that for MDCT (41%) (relative risk (RR): 2.06, 95% confidence interval (CI) 1.07-3.94; P = 0.030). For lymph node involvement, the sensitivity value for EUS (91%) was also significantly higher than that for MDCT (77%) (RR 1.14, 95% CI 1.05-1.23; P = 0.001). However, the specificity values of both EUS and MDCT were quite low, at 49 and 63%, respectively. No significant differences in T2-4 staging between EUS and MDCT were noted. CONCLUSION: This meta-analysis indicates that EUS may be superior to MDCT in preoperative T1 and N staging. Additionally, the low specificity values of EUS and MDCT for N staging merits attention.

Significant Role of Palliative Gastrectomy in Selective Gastric Cancer Patients with Peritoneal Dissemination: A Propensity Score Matching Analysis.

OBJECTIVE: The aim of this study was to explore whether palliative gastrectomy is suitable for gastric cancer patients with peritoneal metastasis, and for patients in whom the type of peritoneal metastasis should be selected to receive palliative gastrectomy. METHODS: A total of 747 patients diagnosed with gastric adenocarcinoma with peritoneal metastasis at our centers between January 2000 and April 2014 were retrospectively analyzed. After propensity score matching, the clinicopathologic characteristics and clinical outcomes of patients with peritoneal dissemination were analyzed. RESULTS: After propensity score matching, the median overall survival (OS) of patients in the gastrectomy group was longer than that for patients in the non-gastrectomy group (11.87 vs. 9.27 months; p = 0.020). Patients who received first-line chemotherapy had a significantly longer median OS than those who did not (11.97 vs. 7.03 months; p < 0.001); among these patients, those undergoing more than eight periods of first-line chemotherapy benefited the most (p < 0.001). Subgroup analyses revealed that patients classified as P1 who were undergoing chemotherapy benefited from gastrectomy (p = 0.024), and patients without multisite metastasis also benefited from gastrectomy with regard to OS (p = 0.007). In the multivariate survival analysis, multisite distant metastasis was the independent poor prognostic factor (p < 0.001), while palliative gastrectomy (p = 0.006) and a period of first-line chemotherapy (p < 0.001) were good prognostic factors. Morbidity rates in the gastrectomy and non-gastrectomy groups were 10.4 and 1.0 %, respectively (p = 0.003); however, no difference in mortality was noted between the two groups (p = 0.590). CONCLUSIONS: Palliative gastrectomy can prolong the survival of P1 patients without multisite distant metastasis when combined with more than five periods, and particularly more than eight periods, of first-line chemotherapy.

Incorporation of N0 Stage with Insufficient Numbers of Lymph Nodes into N1 Stage in the Seventh Edition of the TNM Classification Improves Prediction of Prognosis in Gastric Cancer: Results of a Single-Institution Study of 1258 Chinese Patients.

PURPOSE: This study examined the prognosis of the "node-negative with eLNs ≤ 15" designation and the additional value of incorporating it into the pN1 designation in the seventh edition of the N classification. METHODS: From January 2000 to September 2010, a total of 1258 gastric cancer patients (patients with eLNs > 15 or node-negative with eLNs ≤ 15) undergoing radical gastric resection were enrolled in this study. We incorporated node-negative patients with eLNs ≤ 15 into pN1 and compared this designation with the current 7th edition UICC N stage for 3, 5-year overall survival by univariate and multivariate analysis. Homogeneity, discriminatory ability, and monotonicity of gradients in the hypothetical N stage and the UICC N stage were compared using linear trend χ2, likelihood ratio χ2 statistics, and Akaike information criterion (AIC) calculations. RESULTS: Node-negative patients with eLNs ≤ 15 had worse survival compared with those with eLNs > 15. In univariate and multivariate analyses, the hypothetical N stage showed superiority to the 7th edition pN staging. The hypothetical staging system had higher linear trend and likelihood ratio χ (2) scores and smaller AIC values compared with those for the TNM system, which represented the optimum prognostic stratification. CONCLUSIONS: Node-negative patients with eLNs ≤ 15 can be considered to be incorporated into the pN1 stage in the 7th edition of the TNM classification.