Value Of Radiotherapy In Primary Gastric Cancer And Establishment Of Nomogram Prognostic Model

Background and objective:Several trials have been performed to determine the feasibility of radiotherapy in gastric cancer.However,the absolute benefits of radiotherapy have yet to be determined.In this study,the authors compared the use of radiotherapy in the patients with gastric cancer in the SEER database and established a Nomogram model to assess cancer-specific survival(CSS)in them.Methods:The overall survival of patients with non-metastatic resectable gastric cancer from 2004 to 2013 was analyzed from the SEER database.KaplanMeier survival curves were compared between preoperative,postoperative and non-radiotherapy patients.The Medcalc software was used to draw the receiver working curve(ROC)of lymph node metastasis ratio(LNR),and select the truncation point.The ROC curve was used to evaluate the predictive value of LNR for survival.Based on univariate and multivariate Cox analysis,the important variables were screened to construct Nomogram.Through the C-index,the feasibility of the prediction model was evaluated with the calibration chart.Research results:A total of 9996 patients with gastric cancer were identified through screening.In the entire cohort,the patients receiving preoperative or postoperative radiotherapy had significant survival benefits as compared with the patients who did not receive radiotherapy(log-rank test: preoperative radiotherapy,P = 0.000;postoperative radiotherapy,P = 0.000).For preoperative radiotherapy,the patients’ median survival and 5-year survival rate were 37 months and 39.5% respectively;those for postoperative radiotherapy were 47 months and 46.0% respectively;those for non-radiotherapy were 31 months and 38.9% respectively.There were significant survival benefits in the patients with positive local lymph nodes for both preoperative radiotherapy(P = 0.000)and postoperative radiotherapy(P = 0.000)as compared with those who did not receive radiotherapy.There were significant survival benefits in the patients for postoperative radiotherapy(P = 0.000)as compared with those for preoperative radiotherapy.However,there was no significant survival benefit in the patients with negative local lymph nodes for postoperative radiotherapy as compared with those who did not receive radiotherapy(P = 0.057),but there were significant survival benefits in the patients for postoperative radiotherapy and no radiotherapy as compared those for preoperative radiotherapy(P = 0.000 and 0.002,respectively).The ROC curve showed that the prognostic value for the patients with gastric cancer of lymph node metastasis in the ratio of lymph node metastasis was higher than the number of positive local lymph node metastases.Cox univariate and multivariate survival analysis showed that age,race,tumor grade,tumor histology type,tumor primary site,radiotherapy status,T stage,N stage,and lymph node metastasis ratio were independent prognostic factors of primary gastric cancer,respectively(P = 0.000).Based on the Cox multi-factor analysis model,the Nomogram was established and showed an excellent prediction performance.The C-index was 0.691(95%CI: 0.684-0.697),and the calibration curve was close to the ideal 45o dotted line.Conclusions:Lymph node metastasis ratio(LNR)is an independent and effective predictor of the prognosis of gastric cancer patients,and its prediction effect is more accurate and objective than the number of positive lymph node metastases.Radiotherapy could improve disease-related survival in patients with local lymph node-positive gastric cancer.The construction and verification of Nomogram based on SEER data analysis can effectively predict the survival rate of gastric cancer patients.