CD274 and cancer: The CASPIAN study demonstrated that PD-L1 expression level, a predictive biomarker for ICIs in various cancers, did not correlate with response to ICIs in SCLC.5 Only about 25% of SCLC patients had PD-L1 expression on ≥ 1% on tumor cells.33 This necessitates the exploration for new biomarkers.