The prognostic value of lymph nodes count on survival of patients with node-negative gastric cancer

Robotic versus laparoscopic distal gastrectomy for gastric cancer: A systematic review and meta-analysis

Distal gastrectomy (DG) with lymph node dissection for gastric cancer is routinely performed. In this meta-analysis, we present an updated overview of the perioperative and oncological outcomes of laparoscopic DG (LDG) and robotic DG (RDG) to compare their safety and overall outcomes in patients undergoing DG. An extensive search was conducted using the MEDLINE, EMBASE, PubMed, Web of Science, and the Cochrane Central Register of Controlled Trials from the establishment of the database to June 2023 for randomized clinical trials comparing RDG and LDG. The primary outcome was operative results, postoperative recovery, complications, adequacy of resection, and long-term survival. We identified twenty studies, evaluating 5,447 patients (1,968 and 3,479 patients treated with RDG and LDG, respectively). We observed no significant differences between the two groups in terms of the proximal resection margin, number of dissected lymph nodes, major complications, anastomosis site leakage, time to first flatus, and length of hospital stay. The RDG group had a longer operative time (P < 0.00001), lesser bleeding (P = 0.0001), longer distal resection margin (P = 0.02), earlier time to oral intake (P = 0.02), fewer overall complications (P = 0.004), and higher costs (P < 0.0001) than the LDG group. RDG is a promising approach for improving LDG owing to acceptable complications and the possibility of radical resection. Longer operative times and higher costs should not prevent researchers from exploring new applications of robotic surgery.

Challenging the Dogma: Stage migration or negative lymph nodes, which of them is the main player on gastric cancer prognosis?

Expanding loco-regional nodes harvesting is expected to increase survival. This improvement may be associated to stage migration (SM). However, the great bulk of harvested lymph nodes observed in large dissections is negative. M&M: 830 patients who received R0 gastrectomy for adenocarcinoma were included. pN+ patients with <26 nodes (n = 209) were included for a simulation to "offer 26 nodes" - SM (proportional and exponential based) was simulated and analysed through machine learning algorithms. Overall Survival (OS), in native and simulated stages, were compared. OS of extended lymphadenectomies (pN+, D ≥ 26, n = 273) was compared with the simulated curves. OS of patients in the following dissection intervals of negative nodes were compared: <16 (n = 233), 16-25 (n = 258), ≥26 (n = 339). RESULTS: After simulation to 26 nodes (pN+, D < 26 patients, n = 209), staging was recomputed. OS of native vs simulated early-stages (I-II) and advanced stages (III) were not different (p > 0.05). OS of patients with lymphadenectomy (≥26) was better than simulated for early and advanced stages (p = 0.008; p = 0.005). OS of patients included in distinct intervals of negative lymph nodes were different (p < 0.001). These intervals were an independent prognostic factor (multivariate analysis). CONCLUSIONS: The influence of Stage Migration was null in this set of simulations and Will Rogers phenomenon was not observed. Extended dissection performed better in OS. But the influence of the number of negative nodes, even in large dissections, was highlighted. By emphasizing the role of negative nodes, we aim to facilitate more informed decision-making in management of gastric cancer patients, ultimately leading to improved treatment outcomes and patient care.

Optimizing the Choice for Adjuvant Chemotherapy in Gastric Cancer

Simple Summary

Gastric cancer is the fourth largest cause of tumor-related death worldwide. Despite advances in the management of resectable cancer and improvements in early diagnosis, especially in east Asia where screening campaigns are actively performed, many patients experience recurrence and die because of the disease. Adjuvant systemic chemotherapy is administered after radical surgery in order to reduce the risk of recurrence and death. The modality of administration and regimens of chemotherapy in this setting are different between Eastern and Western countries. In Asia, adjuvant chemotherapy is traditionally given after surgery, while in Europe it is commonly scheduled after preoperative chemotherapy and surgery (perioperative chemotherapy), and in Northern America it is usually combined with radiotherapy (chemoradiotherapy). All these approaches are sustained by well-designed phase III clinical studies, and none may be considered superior to the others in the absence of head-to-head comparisons. The identification of predictive and/or prognostic factors could help to select patients at higher risk of recurrence and those more likely to receive a benefit from the adjuvant treatment. This would allow clinicians to avoid the administration of undue toxicity to non-responder patients and even to reduce the cost of unnecessary treatment.

Abstract

Advances in the management of gastric cancer have improved patient survival in the last decade. Nonetheless, the number of patients relapsing and dying after a diagnosis of localized gastric cancer is still too high, even in early stages (10% in stage I). Adjuvant systemic chemotherapy has been proven to significantly improve outcomes. In the present article we have critically reviewed the clinical trials that guide the current clinical practice in the adjuvant treatment of patients affected by resectable gastric cancer, focusing on the different approaches worldwide, i.e., adjuvant chemotherapy, adjuvant chemoradiotherapy, and perioperative chemotherapy. We also delineate the clinical–pathological characteristics that are commonly taken into account to identify patients at a higher risk of recurrence and requiring adjuvant chemotherapy, and also describe novel biomarkers and therapeutic agents that might allow personalization of the treatment.

Indications for adjuvant chemotherapy in patients with pT1N1M0 gastric cancer: a single-center experience

PURPOSE

Whether adjuvant chemotherapy (AC) has a survival benefit for all patients with pathological stage pT1N1M0 (Stage IB) gastric cancer (GC) remains controversial.

METHODS

All patients with surgically resected, histologically confirmed pT1N1M0 GC between January 2011 and December 2017 at the National Cancer Center, China, were retrospectively reviewed.

RESULTS

A total of 179 patients with pT1N1M0 were identified. Survival analysis showed that both overall survival (OS) and cause-specific survival (CSS) were significantly different between patients treated with and without AC (p < 0.01). Independent risk factors for reduced OS identified in the Cox regression analysis in patients with pT1N1M0 cancer were sex (male sex, hazard ratio [HR] 2.470, 95% confidence interval [CI] 1.294-4.718), examined lymph nodes (EN) (EN ≤ 15, HR 2.402; 95% CI 1.329-4.341), and AC (treated without AC, HR 2.554; 95% CI 1.393-4.681), which were also independent risk factors for reduced CSS. We divided patients with pT1N1M0 into three risk categories (high, moderate, and low) according to two significant prognostic factors (sex and EN) and found that both OS and CSS were significantly different between the three risk groups (p < 0.05).

CONCLUSION

An additional survival benefit related to AC is expected for selected pT1N1M0 patients. Male patients with EN ≤ 15 may be particularly appropriate candidates for AC.

Impact of the number of examined lymph nodes on stage migration in node-negative gastric cancer patients: a Chinese multi-institutional analysis with propensity score matching

BACKGROUND

This propensity score matching (PSM) analysis assessed the influence of examined lymph nodes (ELNs) count on stage migration and survival in node-negative (pN0) gastric cancer (GC) patients.

METHODS

We performed a retrospective analysis of 7,620 GC patients who underwent curative gastric resection in three Chinese medical centers. PSM was used to reduce the confounding effects between the pN0 GC patients with ELNs <16 or ≥16. Survival differences among various subgroups of GC patients were analyzed to assess the impact of the ELNs count on the stage migration in accordance with the overall survival (OS) of pN0 GC patients.

RESULTS

After matching, the backgrounds of pN0 GC patients in the ELNs <16 (n=825) and ELNs ≥16 (n=826) groups were well-balanced. Survival analyses revealed that the ELNs count was positively correlated with the OS (P=0.001). Multiple Cox analysis indicated that the ELNs count was an independent predictor of the OS in pN0 GC patients. Stage migrations were mainly detected in subgroups of pN0 GC patients with specific pTNM stages, as follows: (I) pT2N0M0 with ELNs <16 vs. pT3N0M0 with ELNs ≥16; (II) pT3N0M0 with ELNs <16 vs. pT3N1M0 with ELNs ≥16; and (III) pT4aN0M0 with ELNs <16 vs. pT4aN1M0 with ELNs ≥16.

CONCLUSIONS

We show that stage migration can be detected in pN0 GC patients, and that it could be gradually reduced or prevented by increasing the ELNs count.

The impact of negative lymph nodes in the survival outcomes of pN+ patients following radical gastrectomy: the inverse lymph node ratio as a better score to study negative lymph nodes

The impact of negative lymph nodes (LNs) on survival of pN+ patients has been recognized. The weight of negative LNs in an inverse lymph node ratio (nR) should be related to its prognostic impact. Five hundred and two consecutive gastric cancer patients, who underwent radical gastrectomy, were included. Patients were split into groups according to the number of harvested nodes and a cross-tabulation with pTNM stages was performed to test differences in the tumor burden. pN+ patients (n = 296) were split into groups of negative LNs harvested. We tested an alternative formula for computing a lymph node ratio: nR = total number of harvested nodes/total number of positive nodes. The median number of negative LNs was significantly different (p < 0.01) between dissection groups, but not the median of positive nodes (p > 0.05). No difference in pTNM percentage distribution was found between these groups (p > 0.05). When tested, the overall survival improved significantly for groups with larger numbers of negative LNs (p < 0.001). A cutoff of nR ≥ 6 was an independent prognostic factor for survival (p = 0.001), and the survival of pN+ patients with nR ≥ 6 was not different from pN0 patients. The impact of the number of negative LNs on the survival of the pN+ patients was demonstrated. The higher numbers in the numerator of the nR was due to the disproportion between harvested negative LNs and metastatic LNs. Larger ratios imply more negative lymph nodes in relation to positive lymph nodes, which was significantly associated with survival. We believe that the proposed nR is a friendlier to use format because of its intuitive interpretation.

Effect of lymph nodes count in node-positive gastric cancer

Background: The retrieved lymph node (LN) count has been confirmed as a prognostic indicator in various cancers. However, the correlation between LN counts and patient prognosis in gastric cancer with node-positive is not fully studied. Methods: A total of 8475 patients undergoing gastrectomy in Surveillance, Epidemiology, and End Results Program (SEER)-registered gastric cancer were analyzed. Kaplan-Meier methods and multivariable Cox regression models were used to analyze long-term outcomes and risk factors. Moreover, nomograms including LN counts were established to predict overall survival (OS) and cancer-specific survival (CSS), and Harrell's concordance index (c-index) was adopted to evaluate prediction accuracy. Results: Patients were stratified into 1-6, 7-14, and > 14 subgroups according to the optimal cutoff for retrieved LNs in terms of 5-year CSS. Further analysis indicated that higher LN counts were an independent predictor of longer survival in each N category. Nomograms on CSS and OS were established according to all significant factors, and c-indexes were 0.663 and 0.654 (P< 0.001), respectively. Conclusions: These results indicated that the more the LNs retrieved, the better the survival would be. Nomograms incorporating LN counts can be recommended as practical models to provide more accurate prognostic information for GC patients.

Prognostic Value of the Number of Lymph Nodes Examined in Patients with Node-Negative Gastric Cancer

BACKGROUND

Our aim was to evaluate the prognostic value of the number of lymph nodes examined (eLNs) in patients with node-negative gastric cancer (GC) and further to adjust the American Joint Committee on Cancer (AJCC) 8th staging system based on the number of eLNs.

METHODS

Node-negative GC patients diagnosed during 1988-2015 from the Surveillance, Epidemiology, and End Results (SEER) database were included. On the basis of a primary cohort of 4159 node-negative GC patients, we built the adjusted AJCC 8th staging system, which was then internally validated by a bootstrap method, and externally validated with an independent cohort of 5565 node-negative GC patients.

RESULTS

The median number of eLNs was 10. For the training set, the optimal eLNs thresholds were determined to be 9 for node-negative GC patients. The adjusted AJCC 8th staging system for node-negative GC patients based on the number of eLNs had a significantly higher Harrell's concordance index than the initial AJCC 8th staging system (C-index, 0.635 versus 0.616; P < 0.001). Thus, the adjusted AJCC 8th staging system had superior prognostic stratification. Similar results were found in the validation set.

CONCLUSIONS

For node-negative GC patients in the United States, the adjusted AJCC 8th staging system based on the number of eLNs predicted survival more accurately and discriminatively.

Nodal staging score and adequacy of nodal staging

Aims

The number of lymph nodes (LNs) excised in patients with pathologic N0 is limited, and it is very likely that there will be recessive node disease after surgery, so they are at risk of understaging. The purpose of the present study is to develop a nodal staging score (NSS) in a mathematical way to assess the likelihood that a pathologic N0 gastric cancer (GCa) patient has, indeed, no occult nodal disease after surgery.

Patients and methods

A total of 14,033 stage I-III GCa patients were identified from Surveillance, Epidemiology and End Results database for analysis. A beta-binomial model was fitted to calculate the probability of missing a nodal disease. This probability is then used to calculate the NSS.

Results

The probability of missing a nodal disease is decreased with increasing LNs examined across all pT stages. Seven and 24 LNs removed and examined was enough for an NSS of 90% in pT1 and pT2 patients, respectively, ensuring a high confidence of correct nodal negative classification. Twenty-three and 31 LNs examined in pT3 and pT4 patients could also maintain the NSS at 80%, respectively. NSS had a significant impact on patients' survival across all pT stages (all Ps <0.0001).

Conclusion

The probability that GCa patients are free of true nodal disease could be provided by NSS-based prediction, which is conducive to postoperative decision and survival surveillance. In addition, NSS can define a subtle standard on how many LNs examined are enough for adequate staging dependent on pT stages. However, at least 16 LNs examined is the standard recommendation to date.

Prognostic value of lymph nodes count on survival of patients with distal cholangiocarcinomas

AIM

To evaluate the prognostic value of the number of retrieved lymph nodes (LNs) and other prognostic factors for patients with distal cholangiocarcinomas, and to determine the optimal retrieved LNs cut-off number.

METHODS

The Surveillance, Epidemiology and End Results database was used to screen for patients with distal cholangiocarcinoma. Patients with different numbers of retrieved LNs were divided into three groups by the X-tile program. X-tile from Yale University is a useful tool for outcome-based cut-point optimization. The Kaplan-Meier method and Cox regression analysis were utilized for survival analysis.

RESULTS

A total of 449 patients with distal cholangiocarcinoma met the inclusion criteria. The Kaplan-Meier survival analysis for all patients and for N1 patients revealed no significant differences among patients with different retrieved LN counts in terms of overall and cancer-specific survival. In patients with node-negative distal cholangiocarcinoma, patients with four to nine retrieved LNs had a significantly better overall (P = 0.026) and cancer-specific survival (P = 0.039) than others. In the subsequent multivariate analysis, the number of retrieved LNs was evaluated to be independently associated with survival. Additionally, patients with four to nine retrieved LNs had a significantly lower overall mortality risk [hazard ratio (HR) = 0.39; 95% confidence interval (CI): 0.20-0.74] and cancer cause-specific mortality risk (HR = 0.32; 95%CI: 0.15-0.66) than other patients. Additionally, stratified survival analyses showed persistently better overall and cancer-specific survival when retrieving four to nine LNs in patients with any T stage of tumor, a tumor between 20 and 50 mm in diameter, or a poorly differentiated or undifferentiated tumor, and in patients who were ≤ 70-years-old.

CONCLUSION

The number of retrieved LNs was an important independent prognostic factor for patients with node-negative distal cholangiocarcinoma. Additionally, patients with four to nine retrieved LNs had better overall and cancer-specific survival rates than others, but the reason and mechanism were unclear. This conclusion should be validated in future studies.

Preoperative lymph node size is helpful to predict the prognosis of patients with stage III gastric cancer after radical resection

OBJECTIVE

To investigate the association between preoperative lymph node size (Ns) and prognosis of radical gastrectomy for gastric cancer.

METHODS

The clinical and pathological data of 970 patients undergoing radical gastrectomy for gastric cancer were retrospectively analyzed. The correlation between Ns and the identified variables for the prediction of overall survival (OS) and disease-free survival (DFS) was examined.

RESULTS

Three hundred and thirty-one (34.1%) of 970 patients developed recurrence, which was most commonly in local lymph nodes. The average Ns was 1.52 cm in patients with recurrence, which was significantly higher than the 1.14 cm observed in patients without recurrence (p < 0.001). Patients were categorized into three groups as follows (Ns category):Ns0:≤1.10 cm, Ns1:1.10-1.70 cm, and Ns2:>1.70 cm, determined using the X-tile program. In univariate and multivariate analyses, Ns category, age, tumor size, lymphadenectomy, adjuvant chemotherapy and TNM stage were independent prognostic factors for DFS. Stratified analysis only in stage III was there a significant difference in the Ns category based on TNM stage. Furthermore, in the stage III subgroup, univariate and multivariate analyses revealed that Ns category, lymphadenectomy, and TNM stage was independent prognostic factors for DFS. A nomogram were developed to predict the 3-year DFS rate.

CONCLUSIONS

Preoperative Ns is an independent prognostic factor for DFS of patients after radical surgery for gastric cancer. The proposed nomogram combined with Ns could be a simple and effective approach to predict the 3-year DFS of stage III patients.

The retrieval of at least 25 lymph nodes should be essential for advanced gastric cancer patients with lymph node metastasis: A retrospective analysis of single-institution database study design: Cohort study

BACKGROUND

Recently, increased evidence have shown that the better prognosis of gastric cancer (GC) patients was associated with the larger number of retrieved lymph nodes (RLNs), but the optimal number of RLNs remains controversial. In the present study, we investigated whether adequate LN retrieval (≥15) was necessary to evaluate the prognosis of patients and attempted to propose an appropriate cutoff-point for the number of RLNs.

METHODS

We reviewed 2246 GC patients who underwent radical gastrectomy in our research institution between January 1986 and January 2008. All patients were divided into several groups based on the number of RLNs. The prognostic outcomes of different patient groups were compared and clinicopathologic features were analyzed.

RESULTS

In the present study, our results indicated that ≥15 RLNs showed a better survival outcome than inadequate LN retrieval (<15), regardless of the node-negative or node-positive GC patients (P < 0.001). For the more advanced GC patients (T2-T4 stage, N1-N3 stage, and stage II-stage III), the retrieval of 25-29 LNs could provide a better survival benefit compared with <25 or ≥30 RLNs (P < 0.05). In addition, for the patients who underwent proximal or total gastrectomy, the superior prognosis was still observed in the patient group with 25-29 RLNs.

CONCLUSION

The minimal goal of 15 RLNs may not be enough to accurately evaluate prognosis of all patients and at least 25 RLNs should be necessary for advanced GC patients with lymph node metastasis.

Greater Lymph Node Retrieval Improves Survival in Node-Negative Resected Gastric Cancer in the United States

PURPOSE

Guidelines in western countries recommend retrieving ≥15 lymph nodes (LNs) during gastric cancer resection. This study sought to determine whether the number of examined lymph nodes (eLNs), a proxy for lymphadenectomy, effects survival in node-negative disease.

MATERIALS AND METHODS

The US National Cancer Database (2003-2011) was reviewed for node-negative gastric adenocarcinoma. Treatment was categorized by neoadjuvant therapy (NAT) vs. initial resection, and further stratified by eLN. Kaplan-Meier and Weibull models were used to analyze overall survival.

RESULTS

Of the 1,036 patients who received NAT, 40.5% had ≤10 eLN, and most underwent proximal gastrectomy (67.8%). In multivariate analysis, greater eLN was associated with improved survival (eLN 16-20: HR, 0.71; P=0.039, eLN 21-30: HR, 0.55; P=0.001). Of the 2,795 patients who underwent initial surgery, 42.5% had ≤10 eLN, and the majority underwent proximal gastrectomy (57.2%). In multivariate analysis, greater eLN was associated with improved survival (eLN 11-15: HR, 0.81; P=0.021, eLN 16-20: HR, 0.73; P=0.004, eLN 21-30: HR, 0.62; P<0.001, and eLN >30: HR, 0.58; P<0.001).

CONCLUSIONS

In the United States, the majority of node-negative gastrectomies include suboptimal eLN. In node-negative gastric cancer, greater LN retrieval appears to have therapeutic and prognostic value, irrespective of initial treatment, suggesting a survival benefit to meticulous lymphadenectomy.

Development and Validation of a Nomogram to Predict the Benefit of Adjuvant Radiotherapy for Patients with Resected Gastric Cancer

Background: The US guidelines for gastric cancer (GC) recommend adjuvant radiotherapy (ART) combined with 5-fluorouracil as a standard treatment for patients with resected locally advanced GC. However, patient selection criteria for optimizing the use of adjuvant therapies are lacking. In this study, we developed and validated a nomogram to predict the individualized overall survival (OS) benefit of ART among patients with resected ≥stage IB GC. Patients and Methods: The 2002-2006 Surveillance, Epidemiology, and End Results (SEER) data of 5,206 patients with resected GC were used as a training set for the development of a nomogram. The 2007-2008 SEER data of 1,986 patients with resected GC were used as validation data. Results: In the multivariate analysis weighted by inverse propensity score, the efficacy of ART varied by the ratio of positive to examined nodes (Pinteraction <0.01). The magnitude of this difference was included in the nomogram with associated prognosticators to predict the 3- and 5-year OS with and without ART. The nomogram showed significant prognostic superiority to the 8th TNM staging in the training set (Concordance index, 0.68 versus 0.65; P<0.01) and the validation set (Concordance index, 0.68 versus 0.64; P<0.01). Moreover, the calibration was accurate, and the actual efficacy of ART was positively correlated with the nomogram-estimated survival benefit from ART (Pinteraction <0.01 and Pinteraction =0.02 in the training set and the validation set, respectively). Conclusion: The nomogram can aid individualized clinical decision making by estimating the 3- and 5-year OS and potential benefits of ART among patients with resected GC.

Association of Lymph Node Count and Overall Survival in Node-Negative Endometrial Cancers

Purpose

To estimate whether the number of lymph nodes removed during surgery is associated with overall survival among women with endometrial cancer.

Methods

We performed a retrospective cohort study of women with node-negative, stage I to IIIB endometrial cancer (n = 152,702) identified from the 1998-2011 National Cancer Database. Multivariable Cox proportional hazards regression tested for an association of lymph node count with survival. Restricted mean survival and relative hazard curves were plotted for survival as a function of number of removed lymph nodes.

Results

Among women with node-negative endometrioid endometrial cancer, for each additional five lymph nodes removed, the hazard for death decreased: stage I, the hazard ratio (HR) was 0.95 (95% CI, 0.93 to 0.97; P < .001), stage II, HR was 0.90 (95% CI, 0.87 to 0.94; P < .001); and stage IIIA-B, HR was 0.92 (95% CI, 0.88 to 0.96; P < .001). When grouped by grade, each additional five lymph nodes removed was also associated with decreased hazard for death: grade 1, HR was 0.96 (95% CI, 0.93 to 0.99; P = .009); grade 2,HR was0.91 (95%CI, 0.89 to0.94; P <.001);and grade 3,HR was 0.95 (95%CI, 0.92 to 0.97; P <.001). Increased lymph node dissection was also associated with increased survival among women with node-negative stage II (HR, 0.92; 95% CI, 0.86 to 0.98; P = .01) or stage IIIA-B (HR, 0.94; 95% CI, 0.89 to 0.99; P = .025) uterine serous carcinoma, but not among women with carcinosarcoma or clear cell adeno-carcinoma. Five-year survival for women with one to four nodes removed and endometrioid or serous histology was 85% (95% CI, 84% to 85%) and 54% (95% CI, 50% to 59%), respectively. Five-year survival was significantly higher for women with ≥ 20 removed nodes and endometrioid (91%; 95% CI, 90% to 91%) or serous (72%; 95% CI, 68% to 76%) histology (P < .001).

Conclusion

Increased lymph node count is associated with a 1% to 14% decreased hazard of death per each additional five lymph nodes removed and a 5% to 20% increased 5-year survival among women with pathologically node-negative endometrioid and serous endometrial cancers.

Negative lymph node count is a significant prognostic factor in patient with stage IV gastric cancer after palliative gastrectomy

Negative lymph node (NLN) count has been validated as a protective predictor in various cancers after radical resection. However, the prognostic value of NLN count in the setting of stage IV gastric cancer patients who have received palliative resection has not been investigated. Surveillance, Epidemiology, and End Results Program (SEER)-registered gastric cancer patients were used for analysis in this study. Kaplan-Meier survival curves and multivariate Cox proportional hazards model were used to assess the risk factors for patients’ survivals. The results showed that NLN count and N stage were independently prognostic factors in patients with stage IV gastric cancer after palliative surgery (P< 0.001). X-tile plots identified 2 and 11 as the optimal cutoff values to divide the patients into high, middle and low risk subsets in term of cause-specific survival (CSS). And NLN count was proved to be an independently prognostic factor in multivariate Cox analysis (P< 0.001). The risk score of NLN counts demonstrated that the plot of hazard ratios (HRs) for NLN counts sharply increased when the number of NLN counts decreased. Collectively, our present study revealed that NLN count was an independent prognostic predictor in stage IV gastric cancer after palliative resection. Standard lymph node dissection, such as D2 lymphadectomy maybe still necessary during palliative resection for patients with metastatic gastric cancer.