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The influence of adjuvant radiation therapy after endoscopic resection on survival for early stage EC: an analysis of the surveillance epidemiology and end results (SEER) database.

Background
Endoscopic resection (ER) followed by radiation therapy (RT) is a treatment option for early stage esophageal cancer (EC). We used the surveillance epidemiology and end results (SEER) database to investigate the influence of adjuvant RT after ER on survival for early stage EC.


Methods
The SEER database [1998-2013] was queried for locoregional cases of EC. Tumor staging was redefined with the 8th Edition of the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control tumor-node-metastasis (TNM) staging system. The T1-2 stage EC cases in which ER were followed by radiation or observation were included. Kaplan-Meier methods were performed to compare overall survival (OS) and cancer-specific survival (CSS) between the patients who received radiation and those who did not. Subgroup analysis was made according to AJCC stage. A multivariate Cox proportional-hazards regression model was used to identify independent covariates which may influence survival.


Results
The median survival of the no-radiation group was significantly longer than that of the radiation group [74 vs. 31 months; hazard risk (HR), 2.39; 95% confidence interval (CI), 1.782-3.197; P<0.001]. In T1a stage subgroup, patients who did not receive RT had significantly better OS and CSS outcomes (OS: 90 vs. 31 months; HR, 2.90; 95% CI, 1.766-4.773; P<0.001; CSS: 105 vs. 48 months; HR, 5.40; 95% CI, 2.636-8.226; P<0.001). In the T1b and T2 subgroup analyses, both the OS and CSS were not significantly different between the radiation group and the no-radiation group (all P>0.05). In multivariate regression analysis, radiation was not a significant factor for OS and CSS after adjustment for confounding factors (P>0.05).


Conclusions
Using SEER data, we revealed that RT after ER did not improve survival in early stage EC patients; specifically, RT did not benefit T1b and T2 patients and may lead to poorer survival in T1a patients. Our findings do not support the addition of RT after ER for early stage EC, especially T1a EC.