The HR for OS for PD-L2–positive versus PD-L2–negative patients was 0.50 (95% CI, 0.31−0.82) in unadjusted analyses and 0.44 (95% CI, 0.25−0.79) in multivariate analysis adjusted for age and stage at SCLC diagnosis, ECOG PS, treatment prior to specimen collection, LDH level, and smoking history. This evidence concerns the gene PDCD1LG2 and small cell lung carcinoma.