Immunotherapy uses the certain parts of the patient's own immune system to help fight cancer This can be done in a couple of ways: a. By stimulating patient's own immune system to attack cancer cells; and, b. By giving the immune system synthesized components like immune system proteins to develop a defense mechanism against attack. There are four main types of immunotherapy:

a.  Monoclonal antibodies are synthesized versions of immune system proteins that can be cultivated to attack specific parts of cancer cells.
b.  Immune checkpoint inhibitors are responsible to take the gates and brakes off the immune system to recognize and attack cancer cells.
c.  Cancer vaccines are weaker substances induced in the body to stimulate an immune response to cancer cells.
d.  Non-specific immunotherapies are treatments that boost the immune system in a general fashion.

While cancer is less likely to return with immunotherapy and it can help other treatments work better, the catch is that it may cause considerable side effects, harm other organs and systems, takes time to produce results.