Can our immune system kill cancer cells?

It all Depends: It all depends. The answer is yes and no. It depends on the cause of the cancer, what type of cancer, and the health of the human host. There is no simple answer to this very complicated question.

Yes: In fact, that is why most of us are not afflicted by cancer since cancerous cell mutations occur often. If your immune system is impaired, then the newly mutated cells may survive and proliferate and thus the reason why we are more prone to develop cancer in the later stage of life.

Yes: There is substantial evidence that parts of our immune system can control malignant cells. The problem is that recognition of those cancer cells may not be possible to the immune system, or it may be overwhelmed. This is a very complex issue and not for discussion here. Good question, however, and best wishes.

Yes and no: There is often some immune response to cancers. We pathologists can often see it under the microscope. Almost all cancers evade it eventually. Immune enhancers are highly effective for a minority of melanomas and kidney cancers. The immune response, especially to oat cell carcinoma, can make a person horrendously sick (blind, insane, more). Ignore any 'pop' immune enhancers for cancer.