EGFR and non-small cell lung carcinoma: Current studies regarding the correlation of PD-L1 expression levels in EGFR-mutant NSCLC patients and the clinical outcomes of first- and second-generation EGFR-TKIs have reported that mostly lower expression levels of PD-L1 during pre-treatment can predict a better Objective Response Rate (ORR) and PFS for EGFR-TKIs20,21.