Clinical impact of 22C3 PD-L1 expression in non-small cell lung cancer.

Abstract

149 Background: Immune checkpoint inhibitors has been widely applied in the field of non-small cell lung cancer (NSCLC). Immunostaining of PD-L1 using 22C3 was carried out as a companion diagnosis for Pembrolizumab. To date, only PD-L1 expression thought to be a predictive biomarker approved in USA and JAPAN. However, clinical impact or characteristic of PD-L1 expression in NSCLC is still controversial. In this report, we tried to analyze the relationship between PD-L1 expression and clinic-pathological parameter in NSCLC. Methods: A total 110 of NSCLC samples (Biopsy tissue and surgical resection specimen) were stained with PD-L1 IHC assays by using 22C3 antibody. The expression rate of PD-L1 was examined and relationship between the PD-L1 expression and clinicopathological factors was statistically analyzed. Results: The frequency of Tumor Proportion Score (TPS) less than 1% was 50%, TPS 1 to 49% was 32.7% and TPS 50% or more was 19%. Compared with the previous clinical trials such as KEYNOTE 001 and the KEYNOTE 010, our data of positivity tended to be low. In comparison between histological subtype, the expression in squamous cell carcinoma was higher than non-squamous histology. Furthermore, in relation to smoking history, higher smoking subgroup tended to be higher than the group with low smoking subset. In addition, the specimen preserved for 3 years or longer had a low positive rate, suggesting the possibility of false negatives due to long term formalin fixation of tissue specimens. Conclusions: We examined the relationship between the expression rate of PD-L1 and clinicopathological factors in 110 tissue samples subjected to PD-L1 staining by 22C3 at our hospital. Our results consistent with recent previous studies. In considering to analyze the archived tissue, we recommend that more fresh sample should be use for PD-L1 testing.