A retrospective study of NSCLC patients comprised of both squamous cell carcinoma (SCC) and non-squamous cell carcinoma (adenocarcinoma [ADC]) treated with anti-PD-1 monotherapy showed that patients with liver metastases have shorter PFS and OS compared with patients without liver metastases (hazard ratio [HR] for PFS = 1.62, 95% CI, 1.11-2.36; HR for OS = 1.62, 95% CI, 1.09-2.41) (61). Here, PDCD1 is linked to squamous cell carcinoma.