Cancer immunotherapy aims to enhance or reactivate immune system function by leveraging both adaptive and innate immunity mechanisms. Key approaches to stimulate tumor-specific immune responses include cytokine therapies, cancer vaccines, and immune checkpoint blockade. The field experienced transformative growth after the 2011 approval of ipilimumab (targeting CTLA-4), paving the way for subsequent inhibitors of PD-1 and PD-L1 pathways that demonstrated unprecedented survival benefits across multiple malignancies. These breakthroughs have catalyzed advancements in adoptive T cell therapies, particularly genetically modified CAR T cell infusions showing promising clinical efficacy, signaling a paradigm shift in oncology treatment approaches. Meanwhile, response assessment has faced new challenges. In fact, immunotherapy response patterns often contrast with conventional chemotherapy, particularly regarding phenomena like pseudoprogression, delayed clinical effects, and extended disease stabilization. To address these unique dynamics, revised response assessment guidelines have been established to enhance therapeutic development and clinical decision-making. This chapter examines the progression of immune-specific evaluation standards, their application in clinical trials, and their practical consequences, concluding with insights into future advancements in response classification systems.