The immune system of the body is a natural defense against various diseases, including cancer. It also defends the body against infections and other side effects of cancer treatment. A strong immune system detects the difference between healthy cells and cancer cells, and it can get rid of those that become cancer. The immune system can be strengthened and improved by new immunotherapies. These treatments are designed to repair, stimulate, or increase the body's natural ability to fight infections and cancer.

About 25% of breast cancer patients are noted to have an overexpression of HER2/neu. A recent monoclonal antibody (immunotherapy) treatment called "herceptin" is currently used to reduce the chance of breast cancer recurrence in those patients. Bone marrow transplantation is occasionally recommended for Stage IV breast cancer patients.

As with other types of cancers, immunotherapy is also used as a treatment against breast cancer. To learn more about immunotherapy, see the Cancer Treatment module.