PD-L1 Expression Can Be Regarded As Prognostic Factor for Survival of Non-Small Cell Lung Cancer Patients after Chemoradiotherapy

Inoperable locally advanced non-small cell lung cancer (LA NSCLC) is treated with concurrent or sequential chemotherapy (ChT) and radiation therapy (RT). Survival rates with this treatment remains poor, reported 5-year survival is about 15%. New treatment strategies, including immunotherapy with programmed death ligand-1 (PD-L1) check point inhibitors are being investigated. The clinical significance of PD-L1 expression in tumor samples from patients with inoperable LA NSCLC who underwent concurrent chemoradiotherapy (CRT) in our institution between 2005 and 2010 was evaluated. The expression of PD-L1 was correlated with clinical and pathological parameters and outcome of treatment. We analysed 107 patients treated with concurrent CRT. Only 43 patients (36 males and 7 females) had sufficient tissue for immunohistochemical (IHC) staining. PD-L1 expression was demonstrated in 7 tumors. No statistical significant differences in patient characteristics, including age, smoking status and gender, were found according to the PD-L1 expression. After a median follow up of 103.6 months, median progression free survival (PFS) was 19.9 months in patients without and 10.1 months in patients with PD-L1 expression (p=0.006).Median overall survival (OS) was 28.4 and 12.1 months for PD-L1 negative and PD-L1 positive patients, respectively (p=0.012). In conclusions, PD-L1 expression was negative prognostic factor for PFS and OS after concurrent CRT in LA NSCLC. As only small number of patients had enough tissue for the IHC testing, no firm conclusions could be made and further investigation is warranted.