EGFR and neoplasm: We found that plasma levels of hsa_circ_0006423 in patients with NSCLC before surgery were not significantly related to clinicopathological factors (i.e., gender, age, smoking history, histology, tumor location, tumor size, TNM stage, EGFR, ALK, and PD-L1) but was related to the degree of differentiation (P < 0.001; Table 2); otherwise, tissue levels of hsa_circ_0006423 in patients with NSCLC before surgery was related to the tumor size (P = 0.002; Table 2) and PD-L1 (P = 0.043; Table 2).