"Immunotherapy is a type of cancer treatment that helps your immune system fight cancer. The immune system helps your body fight infections and other diseases."
https://www.cancer.gov/about-cancer/treatment/types/immunotherapy
"Immunotherapy is treatment that uses a person's own immune system to fight cancer. Immunotherapy can boost or change how the immune system works so it can find and attack cancer cells."
https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/immunotherapy.html
"Immunotherapy is treatment that uses certain parts of a person’s immune system to fight diseases such as cancer. This can be done in a couple of ways:
Stimulating, or boosting, the natural defenses of your immune system so it works harder or smarter to find and attack cancer cells
Making substances in a lab that are just like immune system components and using them to help restore or improve how your immune system works to find and attack cancer cells"
"Immunotherapy drugs help your immune system work harder or make it easier for it to find and get rid of cancer cells.
Several immunotherapy drugs have been approved to fight cancer, and hundreds more are being tested in clinical trials (research studies that use volunteers to test new medicines)."
https://www.webmd.com/cancer/immunotherapy-risks-benefits
"Our immune system has the ability to find and destroy cancer cells. But cancer cells can sometimes hide from the immune system and avoid being destroyed. Cancer cells may also stop the immune system from working properly. Immunotherapy helps to strengthen or restore the immune system’s ability to fight cancer.
Immunotherapy is sometimes called biological therapy. You may also hear the term immune-oncology, which is the study of how the immune system interacts with cancer cells in order to find ways to prevent or treat cancer."
https://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/chemotherapy-and-other-drug-therapies/immunotherapy/?region=on