Define cancer immunoediting and its three phases.

• A. Activation, Expansion, Exhaustion
• B. Initiation, Promotion, Progression
• C. Recognition, Destruction, Repair
• D. Elimination, Equilibrium, Escape

Answer: (D)

Cancer immunoediting describes how the immune system interacts with developing tumors through three sequential phases: elimination, equilibrium, and escape. In elimination, the immune system acts as surveillance and destroys transformed cells before they can grow into detectable cancer. Cytotoxic T cells, natural killer cells, and other immune effectors recognize tumor antigens and kill those cells, often with help from cytokines that boost antigen presentation.

If some tumor cells survive, a balance can form in which the immune system contains the cancer without completely eradicating it—this is equilibrium. During this phase, the immune pressure tends to select for tumor variants that are less visible to immune attack, leading to a state where tumor growth is kept in check but not eliminated. Dormant or slowly growing lesions may persist, reflecting a tug-of-war between immune control and tumor cell adaptation.

Eventually, some tumor cells acquire changes that let them grow despite immune forces, leading to escape. They may downregulate antigen presentation, upregulate checkpoint molecules like PD-L1, secrete immunosuppressive factors, or recruit regulatory cells that dampen anti-tumor immunity. This culminates in clinically detectable cancer that continues to progress unless immune responses are strengthened.

Other options don’t describe this triad of immune-tumor interactions. Activation, Expansion, Exhaustion captures stages of T cell responses rather than the overall editing process. Initiation, Promotion, Progression refers to carcinogenesis, not immunoediting. Recognition, Destruction, Repair is not the standard framework for how the immune system interacts with evolving tumors.