The monoclonal antibody Herceptin (trastuzumab) treats a specific type of breast cancer. Herceptin blocks the action of HER2, a protein that stimulates cancer cell growth. Not all breast cancers express this growth protein, and Herceptin is ineffective against those types of cancers.

HER2-Positive Breast Cancer

Approximately one third of breast cancers are HER2-positive, according to the Mayo Clinic. Genetic mutations cause overproduction of human epidermal growth factor receptor-2, which stimulates cancer-cell growth. HER2-positive cancers are more aggressive and less likely to respond to treatment than cancers that do not express HER2.

Action of Herceptin

Herceptin blocks the HER2 receptors and prevents transmission of the chemical signals that trigger cancer cell growth. Herceptin does not directly attack the tumor.

Herceptin in Advanced Breast Cancer

The U.S. Food and Drug Administration (FDA) first approved Herceptin for use in advanced-stage HER2-positive breast cancer. Advanced breast cancer has metastasized to the lymph nodes and other organs.

Expansion of Use

The FDA expanded the indications for Herceptin in 2005 to include early-stage breast cancers with tumors still confined to the breast.

Standard Uses

Herceptin is used in patients with early or advanced HER2-positive breast cancer. It is only used for HER2-positive cancers; it has no effect on cancers that do not express the HER2 protein (ref 2).

Source:

Mayo Clinic. HER2-Positive Breast Cancer: What Is It?

Genentech: Herceptin (trastuzumab)

National Cancer Institute