1.1 About targeted therapy
Targeted therapy is the use of drugs that selectively attack cancer cells, thereby inhibiting tumor growth and achieving the goal of controlling cancer.
Targeted therapy is applied to various types of cancer, including colorectal cancer, lung cancer, etc. In the treatment of breast cancer, there are mainly three categories of drugs:
- Monoclonal Antibody drugs: These drugs work by targeting specific proteins on cancer cells, blocking their growth signals, and stimulating the immune system to attack cancer cells.
- Tyrosine Kinase Inhibitors: These drugs target and block the activity of tyrosine kinases, which are enzymes involved in the growth and division of cancer cells. By inhibiting these enzymes, the drugs can disrupt the signaling pathways that promote cancer cell growth.
- mTOR (Mammalian Target of Rapamycin) Inhibitors: These drugs target the mTOR protein, which plays a role in regulating cell growth and division. By inhibiting mTOR, these drugs can help control the growth of cancer cells.
These targeted therapy drugs are designed to specifically target cancer cells while minimizing damage to healthy cells, which can lead to more effective and less toxic treatment options for cancer patients.
1.2 HER2 gene and testing
HER2, which stands for Human Epidermal Growth Factor Receptor 2, is a group of genes present in cells that are responsible for producing the HER2 receptor protein. The HER2 receptor protein plays a role in controlling cell growth. Medical research has found that some breast cancer tumors exhibit over-expression of the HER2 gene, meaning that cancer cells have replicated an excessive amount of the HER2 gene, resulting in an overabundance of HER2 receptors on the surface of cancer cells. This uncontrolled increase in HER2 receptors leads to uncontrolled proliferation and division of cancer cells, causing the tumor to grow and worsen. Such breast cancer tumors are referred to as HER2-positive breast cancer. Clinical studies have shown that this type of breast cancer generally exhibits faster growth and spread compared to HER2-negative breast cancer.
HER2 Testing
The purpose of HER2 testing is to determine whether a patient’s breast cancer tumor is HER2-positive, in order to assess its responsiveness to HER2-targeted therapies. It is estimated that approximately 20% of invasive breast cancer cases in Hong Kong are HER2-positive. Since drugs like trastuzumab (Herceptin) are only effective for HER2-positive breast cancer cases, HER2 testing is performed before initiating treatment to confirm the HER2 status of the breast cancer and ensure the appropriate treatment approach.
1.3 Monoclonal antibodies
The main principle of monoclonal antibodies in the treatment of HER2-positive breast cancer is to target the HER2 receptors on the surface of breast cancer cells. By doing so, they prevent excessive cell proliferation caused by the overexpression of HER2, effectively inhibiting tumor growth. One commonly used drug is trastuzumab (Herceptin).
Side Effects of Trastuzumab (Herceptin)
Common side effects include:
- Fever
- Headache
- Diarrhea, nausea, vomiting
- Joint and muscle pain
- Skin rash
Other common side effects may include flu-like symptoms, weight loss, loss of appetite, dry skin, and decreased white blood cell count.
Serious complications can occur, particularly related to cardiac function, potentially leading to heart failure.
1.4 Tyrosine kinase inhibitors
The principle of Tyrosine Kinase Inhibitors, which inhibit tyrosine kinase, is to block the HER2 receptors on breast cancer cells, preventing them from receiving signals that control cell growth. The most commonly used drug in this class is Lapatinib (Tykerb).
1.5 mTOR inhibitors
Hormonal therapy is a commonly used treatment for breast cancer. However, over time, the effectiveness of hormonal therapy may be reduced due to the development of resistance. One of the main reasons for this is the activation of a protein called mTOR (mammalian target of rapamycin), which allows cancer cells to continue growing. The role of mTOR inhibitors is to suppress the activity of this protein, thereby inhibiting the growth of breast cancer tumors. The most commonly used mTOR inhibitor is Everolimus (Afinitor).