The Impact of Radiotherapy Parameters on Lymphopenia and Overall Survival in Patients With Esophageal Cancer

Purpose: We sought to perform survival analysis of patients with thoracic esophageal squamous cell carcinoma (ESCC) receiving definitive radiotherapy and identify prognostic factors among hematological and dosimetric factors. Methods: Cases of thoracic ESCC treated with chemoradiation between 2014 and 2017 were identified. The impact of clinicopathological factors’ on overall survival (OS) was analyzed via Cox proportional hazards model. Absolute lymphocyte counts (ALC) and the neutrophil-to-lymphocyte ratio (NLR = ANC/ALC) were assessed before radiotherapy (RT), during RT, and after RT. Cox regression was used to correlate clinical factors with both hematologic toxicities and overall survival. Multiple logistic regression analyses were used to find associations between lymphopenia and dosimetric parameters. The receiver operating characteristics (ROC) curve was used to determine cut-off points. Results: Ninety-nine ESCC patients were enrolled with the median overall survival of 23 months. The median RT dose was 55.75Gy(46–66Gy), and the mean does (D mean ) of thoracic vertebrae dose (TVB) was 27.04±9.65Gy. Based on multivariate analysis, V20 of TVB, pretreatment NLR, and ALC nadir were associated with a worse OS significantly. Concurrent CRT, increasing mean TVB dose and V20 of TVB were associated with higher odds of lymphopenia risk (P＜0.05) through multiple logistic regression analysis. Conclusions: In ESCC patients who received definitive RT, V 20 of TVB, pretreatment NLR, and ALC nadir during RT were independent prognostic factors and chemotherapy regimen, mean TVB dose, and V 20 of TVB were associated with lymphopenia.