PDCD1 and small cell lung carcinoma: The result showed that PIV was an independent predictive factor for PFS and OS among the SCLC patients treated with anti-PD-1/PD-L1 inhibitor combined with chemotherapy (PFS: HR = 2.157, 95% CI: 1.181–3.940, p = 0.012; OS: HR = 2.359, 95% CI: 1.168–4.762, p = 0.020).