CD274 and small cell lung carcinoma: Subgroup analyses investigating whether PD-L1 score or TMB could help to select patients who experienced the longer benefit with ICI were unfortunately negative [145,218,219] On the other hand, the low expression of MCH-I in SCLC (about 15%) helped us to recognize one of the main causes of ICI failure in SCLC in terms of immune system evasion [83].