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Targeted Therapy

In recent years clinical trials have been conducted to evaluate the effectiveness of new drugs that alter the behavior of the breast cancer cell. These drugs are referred to as targeted therapy or biologic targeted therapy.

During the clinical trial, the pathologist performs a special prognostic factor called HER2neu receptor on the invasive breast cancer cells. This receptor stands for human epidermal growth receptor 2. It is a gene that helps control how cells grow, divide and repair themselves. The HER2 gene (not to be confused with BRCA 1 or 2 genes) directs the production of a special protein. This gene is designed to help the breast cell grow normally. However, if there are too many copies of the gene within the cell, the breast cells then have the ability to turn into a breast cancer cell. Those breast cancers that are HER2neu positive are considered more aggressive.

Special tests referred to as immunohistochemistry (IHC) or FISH (Fluorescence in situ Hybridization) are used by the pathologist to determine if the breast cancer cells are HER2/neu positive or negative. If positive, a patient may be advised to take targeted biologic therapy.

Two types of targeted biologic therapy:

  • Herceptin® (trastuzumab) – This drug binds to the HER2 receptors on the surface of the cell to prevent it from overproducing the protein that is causing the problem. It can also limit the breast cancer cell’s ability to grow and subdivide. Herceptin works in multiple ways: to block tumor cell growth; to try to target the cell for destruction by the immune system; or it may work with chemotherapy to destroy the HER2neu positive cancer cells. This drug can be given alone or with specific chemotherapy agents. It is not unusual for a patient to be advised to take this drug for a year. It is given intravenously, usually in combination with chemotherapy.
  • Pertuzumab