A wide range of approaches have been explored to develop predictive biomarkers for ICIs, including analyses of PD-L1 or PD-1 expression on tumour cells and infiltrating lymphocytes41,42, the pattern of lymphocytic infiltration as reflected in an “immunoscore”11, tumour mutational burden11,43, microbiome44 and consideration of clinical features such as use of steroids and antibiotics. This evidence concerns the gene PDCD1 and neoplasm.