CD274 and non-small cell lung carcinoma: Avoiding sample bias is particularly important because of the different patient eligibility criteria of the four clinical trials: specifically, except that the BIRCH and FIR trials contained a fraction of PD-L1-positive (PD-L1 ≥ 5%) advanced NSCLC patients with no prior chemotherapy, all trials recruited advanced NSCLC patients who underwent platinum-based therapy.