You were right! There is immunotherapy.

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 your own immune system to work harder or smarter to attack cancer cells
Giving you immune system components, such as man-made immune system proteins
Some types of immunotherapy are also sometimes called biologic therapy or biotherapy.

In the last few decades immunotherapy has become an important part of treating some types of cancer. Newer types of immune treatments are now being studied, and they’ll impact how we treat cancer in the future.

Immunotherapy includes treatments that work in different ways. Some boost the body’s immune system in a very general way. Others help train the immune system to attack cancer cells specifically.

Immunotherapy works better for some types of cancer than for others. It’s used by itself for some of these cancers, but for others it seems to work better when used with other types of treatment.

this article is from
https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/immunotherapy/what-is-immunotherapy.html