The present invention provides diagnostic methods, therapeutic methods, and compositions for the treatment of cancer. The invention is based, at least in part, on the discovery that an immune-score expression level based on one or more of PD-L1, CXCL9, IFNG, GZMB, CD8A, and PD-1 in a sample obtained from an individual having cancer can be used in methods of predicting the therapeutic efficacy of treatment with a PD-L1 axis binding antagonist (e.g., a PD-L1 binding antagonist (e.g., anti-PD-L1 antibody, e.g., atezolizumab (MPDL3280A)) or a PD-1 binding antagonist (e.g., anti-PD-1 antibody)).