Cancer immunotherapy is a treatment that uses the body's immune system to fight cancer. Cancer cells have the ability to invade the immune system through a variety of mechanisms. Immunotherapy focuses on these mechanisms and develops another mechanism to restore the immune system and its ability to destroy cancer cells. Cancer immunotherapy is a cancer treatment that strengthens the immune system's ability to fight cancer. This treatment is preferred over older techniques because it provides long-term protection against cancer, has fewer side effects, and treats a wider range of cancers.