In a similar approach, Xing et al. [189] and Niemeijer et al. [190] investigated the correlation between PD-L1/PD-1 expression based on single photon emission computed tomography (SPECT), PD-L1/PD-1 PET and PD-L1/PD-1 expression assessed by immunohistochemistry (IHC) in NSCLC patients. The gene discussed is PDCD1; the disease is non-small cell lung carcinoma.