Immune oncology trials on ICIs and CAR-T have identified a number of variables potentially influencing the immunotherapy outcome; among them, some are potentially prognostic, such as: tumor cell biology and mutational burden, presence of an inflammatory tumor microenvironment (TME) recruiting tumor-fighting CD8+ T cells, antigen loss and immune escape, fitness of the immune system and timing of administration of the immunotherapy. This evidence concerns the gene CD8A and neoplasm.