Changes in tumour expression of programmed death-ligand 1 after neoadjuvant concurrent chemoradiotherapy in patients with squamous oesophageal cancer

Background Programmed death-ligand 1 (PD-L1) expression has been suggested as a potential predictive biomarker of response to anti-PD-1/PD-L1 therapy. In this study, we investigated whether the expression of PD-L1 in tumour cells is affected by neoadjuvant concurrent chemoradiotherapy (CCRT) or chemotherapy in oesophageal squamous cell carcinoma. Patients and methods Between 2004 and 2014, we collected the medical records of locally advanced oesophageal cancer patients consecutively diagnosed and treated with neoadjuvant CCRT or chemotherapy, followed by curative resection. PD-L1 expression in acquired tissue specimens was evaluated by immunohistochemistry using the H-score. The changes in PD-L1 expression between paired samples were evaluated and we also analysed PD-L1 expression in surgical tumour specimens to evaluate its prognostic role. Results Twenty-eight paired tumour tissues that were acquired before and after neoadjuvant therapy were available: 19 patients with CCRT and 9 with chemotherapy before complete oesophagectomy. The PD-L1 H-score increased significantly from baseline tumour tissues to surgical tumour tissues after neoadjuvant CCRT (P = 0.007, median H-score from 28 to 52), whereas it decreased significantly after neoadjuvant chemotherapy (P = 0.048, median H-score from 53 to 22). In a total of 73 patients, including 45 additional cases for the prognosis analysis, patients with higher PD-L1 H-scores (≥20) had poorer overall survival (median 16.7 versus 32.9 months, P = 0.02) than those with lower H-scores (<20). Conclusions PD-L1 expression in tumour cells increased in oesophageal cancer patients who received neoadjuvant CCRT. Further studies with more cases are necessary to validate these findings.