Herceptin (chemical name: trastuzumab) is the only immune treatment currently available for breast cancer. It is considered an immune treatment because it helps the immune system fight the cancer. It does this by giving the body an antibody that can help slow down or stop the growth of cancer cells.

Herceptin works only against breast cancers that make too much of the HER2/neu, or HER2, protein. These cancers are called "HER2 positive." About one out of every four breast cancers is HER2 positive.

Herceptin is approved by the U.S. Food and Drug Administration (FDA) for women with metastatic HER2 positive breast cancer, and it is available in clinical trials for women with early-stage HER2 positive breast cancer involving lymph nodes.

Research studies have shown that Herceptin often works better in combination with different types of chemotherapy.

In this section you'll learn more about how Herceptin works, who can benefit from it, how you get it, and what the side effects are.

The medical expert for Herceptin is Jennifer Griggs, M.D., medical oncologist and breast cancer specialist, University of Rochester Cancer Center, Rochester, NY.