All About Targeted Therapy
What is targeted therapy?
Targeted therapy is a type of cancer treatment. Targeted therapies use drugs to target genes and proteins that control how cancer cells grow, divide, and spread. This slows down or kills the cancer cells while preserving the normal cells as much as possible. Sometimes the “target” is found on some healthy cells as well, and side effects can happen.
Targeted therapy can be called precision medicine or personalized medicine. This is because one person’s cancer may be treated differently than another based on the targets found on their tumor. In many cases, your healthcare provider will have to test your tumor to see if a specific target is present. Targeted therapy is effective, but it does not always work. Here are some examples:
- The same type of cancer does not always have the same molecular targets that match the treatment.
- The same targeted treatment doesn’t work for everyone with the same type of cancer. Some tumors react to the therapy differently.
- Even though the target is present, it does not mean the tumor will respond to the targeted therapy.
Common molecular targets (mutations or changes) that are treated with targeted therapies include HER2, EGFR, KRAS, VEGF, ALK, JAK 1 and 2, BTK, and BRAF. Your healthcare team may test for these mutations, depending on your cancer type and if a mutation is known in that cancer type.
Targeted therapies are currently FDA-approved for the treatment of many cancers. Targeted therapy may be given alone or given with chemotherapy, radiation, and/or surgery.
What are the types of targeted therapies?
There are different types of targeted therapy, and each type works a little differently. Some targeted therapies work by focusing on the inside of the cancer cell while other focus on the outside of the cancer cell. The two most common types of targeted therapy are small-molecule drugs and large-molecule drugs.
- Small-molecule drugs focus on the inside of the cancer because of how small they are. They find the target, enter the cell, and block it causing it to die.
- Large-molecule drugs often don’t fit into a cell. They focus on the outside of the cancer cell by attacking the proteins or enzymes on the surface of the cell causing them to die.
Examples of targeted therapies include:
- Kinase Inhibitors: Cell growth is controlled by growth factors. They attach to the surface of cells triggering a series of chemical reactions that allow the cell to grow and divide. Cancer cells do not work properly and are able to grow and divide even when growth factors are not present. Kinase inhibitors work by blocking signals within cancer cells, preventing a step needed for the cell to grow and divide. Examples of kinase inhibitors include dabrafenib (Tafinlar®), imatinib (Gleevec®), sorafenib (Nexavar®), ibrutinib (Imbruvica), and cabozantinib (Cometriq).
- Angiogenesis Inhibitors: Angiogenesis is the development of blood vessels to supply the tumor with the nutrients it needs to grow. These medications work to block the formation of this blood supply and cut off the tumor's source of nutrients. Some kinase inhibitors also act as angiogenesis inhibitors (examples: sorafenib (Nexavar), sunitinib (Sutent®), everolimus (Afinitor®). Examples of angiogenesis inhibitors include ziv-aflibercept (Zaltrap®), lenalidomide (Revlimid®), and vandetanib (Caprelsa®).
- Monoclonal antibodies: These antibodies are made in a lab and target a specific antigen (protein). They work in a few different ways. They can target a specific cell (the cancer cell), sending a message to the immune system to destroy the targeted cell. Some monoclonal antibodies slow or stop the growth of cancer cells by interfering with functions necessary for cell growth. Examples of monoclonal antibodies are bevacizumab (Avastin®), trastuzumab (Herceptin®), and denosumab (Xgeva®, Prolia®).
- Radioimmunotherapy: This is a combination of a monoclonal antibody and a radiation source, which allows radiation to be delivered directly to the targeted cells, but often in lower doses and over a longer period. An example is ibritumomab tiuxetan (Zevalin®).
How are targeted therapies given?
Some targeted therapies are given by pill, others are given by vein (IV). Be sure to store and handle oral medications as instructed. It is important that you take your oral medications exactly as your provider instructs you to.
Some oral medications are very expensive. Talk with your care team if you can’t afford your medication, help may be available.
What are the side effects of targeted therapies?
There are side effects to targeted therapies. Not everyone will have the same side effects. Talk with your healthcare provider about which side effects you may have.
Side effects are different for each drug and differ depending on how your body reacts to it. Some side effects to targeted therapies are:
- Skin problems, including dry skin or rash.
- Liver problems.
- Heart problems.
- High blood pressure.
- Problems with wound healing and blood clotting.
- Nail changes.
- Loss of hair color.
- Gastrointestinal (GI) perforation.
Do not stop taking your oral medications due to side effects. If you are having side effects talk with your healthcare provider, there are medications that can help. Most short-term side effects will go away over time once you are done with treatment.
Because many of these drugs are newer, we don’t know a lot about the potential for long-term side effects. Be sure to talk with your healthcare team about fertility preservation before starting any targeted therapy, as these medications may impact your ability to have a child. Certain targeted therapies like thalidomide and lenalidomide can cause serious birth defects and have special programs in place to educate patients and encourage safe distribution to patients of childbearing age.
How will I know if targeted therapy is working for me?
It is possible that over time, you may build up resistance to the targeted medication you are receiving. This may happen more frequently when targeted therapy is the only therapy being received. Your healthcare team will continue to monitor your disease closely throughout your treatment. You will have regular blood and imaging (CT scan, PET scan) tests that will tell how your body is responding to treatment.
Resources for More Information
- American Cancer Society: Targeted Therapy http://www.cancer.org/treatment/treatmentsandsideeffects/treatmenttypes/targetedtherapy/index
- National Cancer Institute: Targeted Therapy Fact Sheet http://www.cancer.gov/about-cancer/treatment/types/targeted-therapies/targeted-therapies-fact-sheet
- National Cancer Institute: List of Targeted Therapy Drugs Approved for Specific Types of Cancer https://www.cancer.gov/about-cancer/treatment/types/targeted-therapies/approved-drug-list
- American Society of Clinical Oncology (ASCO): Understanding Targeted Therapy http://www.cancer.net/navigating-cancer-care/how-cancer-treated/personalized-and-targeted-therapies/understanding-targeted-therapy
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