Targeted Chemotherapy

Most chemotherapy drugs work by killing cells that are actively growing and dividing.  Since cancer cells are characterized by abnormal rates of growth and division, they are often more susceptible to the action of chemotherapy drugs than most normal cells in your body.  Some of these normal cells, however, do divide rapidly and they too can be damaged by chemotherapy.  These include blood cells, bone marrow, hair follicles, and the cells that line the mouth and digestive tract. 

To avoid damage to these healthy, normal cells, new therapies are being developed to target cancer cells more accurately.  One of the primary goals of cancer research is to identify specific characteristics of cancer cells that distinguish them from normal cells.  These characteristics of genes, proteins and the tissue environment are targeted with drugs or agents that affect only the cancer cells. The understanding of cancer cell growth and division has increased significantly in recent years, and a number of targeted therapies for breast cancer have been developed as a result.  The most commonly used and successful of these therapies targets the HER2 gene.
 

HER2 Targeted Therapy
HER2 is a gene that helps regulate the rate of cell growth and division.  Some cancers have too many copies of this gene.  When that occurs, HER2 produces too much of a protein that is said to be overexpressed.  This condition leads to an increased, abnormal rate of cell growth and division.  Approximately 25% of all breast cancers over express the HER2 protein and are called HER2 positive (HER2+).  HER2+ breast cancers tend to be more aggressive and more likely to recur, but the HER2 receptors on the surface of cells provide a target for anti-cancer drugs, making it easier to treat. 

Your pathology report will include your HER2 status.  You should know if you are HER2 positive or negative (HER2+/-) and discuss the implications with your doctor. 

The most common drug used to target HER2+ breast cancer is called trastuzumab (brand name Herceptin).  It is used to treat early stage breast cancers as adjuvant therapy as well as for breast cancers that have spread or metastasized.  HER2 therapy for advanced or metastatic breast cancer is discussed in the section on that topic. 

When Herceptin is given as adjuvant therapy for early stage breast cancer, it is generally combined with chemotherapy.  The combination of Herceptin and chemotherapy has been shown to be very effective in reducing the recurrence rate in women who have HER2+ breast cancer. 

Herceptin does have side effects, although they are generally mild.  It can cause flu-like symptoms, including achiness, fever and nausea.  The most serious side effect is the risk of heart problems, some of which can be permanent.  These problems occur in approximately 2-5% of patients taking the drug.  If you are taking Herceptin, your doctor will monitor your heart function very carefully.

A second HER2 targeted therapy, lapatinib (brand name Tykerb), is also effective in treating patients with HER2+ breast cancer.  This drug has been used primarily for metastatic disease but has been tested in early stage breast cancers.  It is also used in the treatment of inflammatory breast cancers.
 

Triple Negative Breast Cancer
Triple negative breast cancer refers to a type of invasive breast cancer that is estrogen receptor negative (ER-), progesterone receptor negative (PR-), and HER2 negative (HER2-).  Between 10-20% of breast cancers are triple negative, and occur more often in younger women and African-American women.  They are generally more aggressive and higher grade – and in some respects, more difficult to treat.  The lack of hormone receptors means that these cancers cannot be treated effectively with hormone therapy.  HER2- breast cancers do not respond to treatments targeted to the HER2 receptors.  Triple negative breast cancers can be treated effectively with chemotherapy and radiation therapy.  Researchers are investigating improved ways to treat triple negative breast cancers, especially with targeted therapies.

Next: Anxiety About Chemo.