Immunotherapy is a form of cancer treatment that mobilizes the patient’s own immune system to recognize and destroy tumor cells. Unlike chemotherapy and radiotherapy, which directly target rapidly dividing cells, immunotherapy modifies immune responses, often achieving longer lasting control and sometimes complete remission.

Several main strategies are in clinical use or advanced development. Immune checkpoint inhibitors block inhibitory receptors such as CTLA‑4 and PD‑1 or its ligand PD‑L1, which tumors exploit to silence T cells. By releasing these brakes, cytotoxic T cells can attack cancer more effectively. These drugs have transformed the management of melanoma, lung cancer and several other malignancies, though only a subset of patients benefit and immune‑related side effects can be serious.

Adoptive cell therapies engineer or expand a patient’s immune cells outside the body and reinfuse them. Chimeric antigen receptor T cells, or CAR‑T cells, are designed to recognize specific surface molecules on cancer cells. They have produced high response rates in certain leukemias and lymphomas, but face challenges in solid tumors, such as limited penetration and immune suppression within the tumor microenvironment.

Cancer vaccines and oncolytic viruses aim to enhance tumor visibility to the immune system. Vaccines present tumor antigens to stimulate targeted T cell responses, while oncolytic viruses selectively infect and lyse cancer cells, releasing additional antigens and inflammatory signals.

Current research focuses on optimizing combinations of immunotherapies with each other and with conventional treatments, identifying biomarkers to predict who will respond, and mitigating toxicity. The overall goal is to convert more cancers into controllable or curable diseases by harnessing durable, highly specific immune responses.