PD-L1 Expression and the Effect with Radiosensitivity and Prognosis in Esophageal Squamous Cell Carcinoma

Abstract

The relationship between PD-L1 expression and the clinical biological behavior of esophageal squamous cell carcinoma (ESCC) has been widely debated. The purpose of the research was to investigate the relationship of PD-L1 with clinicopathological characteristics, radiotherapy response, and prognosis of patients with ESCC. The expression of PD-L1 was detected by immunohistochemical staining, both on cancerous and normal esophageal mucosal cells. Esophagus barium meal X-ray examinations were applied to evaluation radiotherapy response lines with PD-L1 expression in ESCC. Progress-free survival (PFS) and Overall survival (OS) were analyzed by Kaplan-Meier method. Differences between pairs of Kaplan-Meier curves were examined by the log-rank test. The chi-square test was used to compare correlations between pathological characteristics and PD-L1 expression. P value of 0.05 was considered statistically significant. A total of 90 patients with ESCC were included. PD-L1 staining was observed on tumor cells (56.7%), as well as normal esophageal mucosal cells (15.0%). PD-L1 protein expression was not correlated with age, gender, the maximum diameter of tumor, the length of tumor, the local aggressive of tumor, clinical stage and primary tumor volume (P > 0.05 ), it was statistically correlated with the lymphatic metastasis (P < 0.05)．Patients with positive PD-L1 expression was sensitive to radiation( P < 0.05). Single factor analysis found that the maximum diameter of tumor, radiosensitivity and GTV-T were correlated with PFS (P =0.013, P= 0.008, and P= 0.012) and OS (P =0.004, P= 0.039, and P= 0.025) of ESCC patients. However, PD-L1 expression levels was not correlated with PFS (P =0.953) and OS (P =0.952) of ESCC patients. The results of multifactor analysis showed that the radiosensitivity and the maximum diameter of tumor affected PFS (OR=0.512, 95% CI=0.275∼0.954, P =0.035) and OS (OR=0.507, 95% CI=0.266∼0.968, P =0.039) in ESCC patients, respectively. The level of PD-L1 protein expression in ESCC tissues increased comparing to the normal esophageal mucosa tissues of normal people. PD-L1 may be a novel predictive marker for response to the radiotherapy and metastatic potential in patients with ESCC. However, positive PD-L1 cannot as one of prognosis predictors in ESCC patients accomplished curative radiotherapy.