Does a Cancer Diagnosis Mean the Beginning of the End?" Nature of the Study: It is a conceptual and documentary review designed to connect basic tumor immunology with modern clinical immunotherapies. Main Objective: To build a coherent conceptual bridge between basic tumor immunology and clinic-based immunotherapies, and to reconsider the common assumption that a cancer diagnosis is inevitably a terminal trajectory. Scope of the Study: It focuses on general mechanisms and principles across tumor types (using melanoma, lung cancer, and hematologic malignancies as illustrative examples) rather than providing an exhaustive clinical analysis or economic health-policy evaluation. Theoretical Framework: It is organized into three core chapters covering immune surveillance, mechanisms of tumor immune evasion, and immunotherapy from concept to clinical application. Study Model: It employs a four-stage conceptual trajectory model spanning immunosurveillance, immune equilibrium, immune evasion/escape, and therapeutic re-engagement.