The Exploration Of Preoperative Radiotherapy In The Locally Advanced Rectal Cancer With Different CEA Levels And Screening Of Benefit Groups

Objective: This study was designed to analyze the clinical features,prognostic factors and survival value of preoperative radiotherapy in locally advanced rectal cancer(LARC)with different levels of carcinoembryonic antigen(CEA).The survival and prognosis of LARC patients with normal CEA,especially the influence of preoperative radiotherapy.To provide more evidence for the individualized treatment of LARC with normal CEA.Methods and Materials:LARC patients either receiving or not receiving preoperative radiotherapy followed by surgery between 2011 and 2015 were identified in the Surveillance,Epidemiology,and End Results database(SEER).An analysis of overall survival(OS)was performed using Kaplan–Meier(KM)curves stratified by CEA level,and further analysis was conducted among subgroups of patients with normal CEA levels as training set.250 cases collected in our hospital were used as verification set,and the prediction ability of nomogram was verified by C-index and calibration curves.Based on the established Nomogram model,the KM curve of each risk group was plotted and analyzed by stratification.Subgroup analysis was performed for patients who received or did not receive preoperative radiotherapy and stratified for each variable,including the AJCC 8th edition TNM staging system and Nomogram risk group.The final results are shown in a forest map.Results: 1.In total,4262 patients were eligible for this study.In normal CEA group,63.41% was phase III,8.2% was T4,11.4% was tumor deposits positive,10.17% had perineural invasion,which accounted for less than that in the CEA elevated group.The KM survival curves showed only a significant difference for the subgroup with elevated CEA levels(P < 0.05)but not in the whole cohort or subgroup with normal CEA levels(both P > 0.05).2.The normal CEA group in SEER database was used as the training set.Using a multivariate Cox regression model,race,age,tumor differentiation,T stage,N stage,tumor deposits,and perineural invasion were independently associated with poor OS for patients with normal CEA levels(all P < 0.05).A nomogram was established based on the multivariate analysis,and it showed better calibration than that of the 8th American Joint Committee on Cancer(AJCC)staging system for patients with normal CEA levels.The C-index of nomogram model is 0.670.The C-index of the model based on nomogram for predicting overall survival was 0.659 in the validation set.The calibration curve showed that the actual survival rate was consistent with the predicted survival rate,indicating that the prediction effect of the model was good.3.Further analysis showed that among patients with normal CEA levels,preoperative radiotherapy benefited only those with normal CEA levels who were at high risk(P < 0.05),not patients at low risk(P > 0.05).Conclusions: In the current study,we concluded that preoperative radiotherapy benefits the majority of LARC patients,but patients with normal CEA levels and low risk might not need radiation-based neoadjuvant modality.