IDO1 and non-small cell lung carcinoma: According to the agreement statistics [28, 29], PD-L1 (κ = 0.61, 95% CI 0.13–1.00, P = 0.007) and B7-H4 (κ = 0.53, 95% CI 0.15–0.92, P = 0.024) had moderate consistency in primary NSCLC and its brain metastases, and the expressions of B7-H3 (κ = 0.43, 95% CI 0.03–0.83, P = 0.059), IDO1 (κ = 0.38, 95% CI − 0.07–0.83, P = 0.115), and EphA2 (κ = − 0.04, 95% CI − 0.49–0.41, P = 0.858) in primary NSCLC and its brain metastases were not consistent (Details are shown in Table 2).