| |
Targeted Therapy Drugs
|
 |
Cancer
|
Our bodies are made up of many tiny units called cells, which are arranged into tissues and organs. Tissue and organ growth (in children) and repair (in adults) are generally the result of cells growing in size and dividing into two cells in a controlled manner. Chemical signals tell the cells to divide or stop dividing.
|
Cancer is a condition where cells in a specific part of the body grow and reproduce uncontrollably. Rather than responding appropriately to the signals that control normal cell behavior, cancer cells grow and divide in an uncontrolled manner. The cancer cells can invade and destroy surrounding healthy tissue, including organs. Cancer sometimes begins in one part of the body and then spreads to other areas. This process is known as metastasis. There are over 200 different types of cancer, each with its own methods of diagnosis and treatment. |
Cancer is a leading cause of death in Hong Kong, accounting for 30.5% of all deaths in 2012. Altogether 13,336 died from cancer in 2012. The number of cancer deaths in HK rose at an average annual rate of 1.4% between 2002-2012. The five most commonly diagnosed cancers were those of the lung (16.6%), colorectum (16.4%), breast (12.6%), liver (6.4%) and prostate (5.9%). These 5 leading cancers comprised nearly 60% of all cancers newly diagnosed in Hong Kong. |
|
|
▲ back to top
Treatment |
Surgery is the primary treatment option for most types of cancer, because solid tumours can usually be surgically removed. Two other commonly used treatment methods are chemotherapy (uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing) and radiotherapy (uses high-energy X-rays or other types of radiation to kill cancer cells or keep them from growing).
|
|
|
▲ back to top
|
Targeted therapy drugs |
Targeted therapy drugs, like any drugs used to treat cancer, are technically considered chemotherapy. But targeted therapy drugs do not work in the same ways as standard chemotherapy drugs. Targeted therapy drugs interfere with specific molecules (targets) that are involved in cancer cell growth and survival. Traditional chemotherapy drugs, by contrast, act against all actively dividing cells. Therefore, targeted therapy drugs may have fewer side effects than traditional chemotherapy drugs.
|
Not all cancer patients are candidates for targeted therapy. The use of a targeted therapy may be restricted to patients whose tumour has an appropriate target for a particular target therapy drug. Sometimes, a patient is a candidate for a targeted therapy only if he or she meets specific criteria (for example, their cancer did not respond to other therapies, has spread, or is inoperable).
|
Sometimes targeted therapy will be the only treatment you need. But in most cases, targeted therapy is used along with other treatments such as traditional chemotherapy, surgery, and/or radiotherapy.
|
Most targeted therapy drugs are either small molecules or monoclonal antibodies. Small molecules are chemicals typically developed for targets that are located inside the cell because such agents are able to enter cells relatively easily. Monoclonal antibodies are relatively large immune system proteins and generally cannot enter cells, so they are used only for targets that are outside cells or on the cell surface.
|
|
The most common ways to give targeted therapy drugs are by mouth (as a tablet or capsule) or into a vein (intravenously). A few targeted therapy drugs might be injected under the skin (subcutaneously).
|
|
|
|
▲ back to top
Principles of targeted therapy drugs
|
|
 |
| Targeted therapy drugs can be grouped by how they work or which part of a cell they target at. A few of the more common types of targeted therapy drugs are listed below, but this is not a complete list: |
|
Signal transduction inhibitors
Signal transduction inhibitors block the activities of molecules that participate in signal transduction, the process by which a cell responds to signals from its environment. In some cancers, the malignant cells are stimulated to divide continuously without being prompted to do so by external growth factors. Signal transduction inhibitors interfere with this inappropriate signaling.
|
Angiogenesis inhibitors
Angiogenesis is the formation of new blood vessels. Blood supply is necessary for tumours to grow beyond a certain size because blood provides the oxygen and nutrients that tumours need for continued growth. Angiogenesis inhibitors block the growth of new blood vessels to tumours and thus may block tumour growth.
|
Apoptosis-inducing drugs
Apoptosis-inducing drugs cause cancer cells to undergo a process of controlled cell death called apoptosis. Apoptosis is one method the body uses to get rid of unneeded or abnormal cells, but cancer cells have strategies to avoid apoptosis. Apoptosis-inducing drugs can get around these strategies to cause the death of cancer cells.
|
Immunotherapy drugs
Immunotherapy drugs trigger the immune system to destroy cancer cells. Some immunotherapy drugs are monoclonal antibodies that recognize specific molecules on the surface of cancer cells. Cells that express a target molecule will be destroyed when monoclonal antibody binds to the target molecule. Other monoclonal antibodies bind to certain immune cells to help these cells to kill cancer cells.
|
Monoclonal antibodies attached to toxins
Monoclonal antibodies that deliver toxic molecules can cause the death of cancer cells specifically. Once the antibody binds to its target cell, the toxic molecule that is linked to the antibody — such as a radioactive substance or a poisonous chemical — will be taken up by the cell and ultimately kills that cell. The toxin will not affect cells that lack the target for the majority of cells in the body will not be affected.
|
|
▲ back to top
Targeted therapy drugs registered in Hong Kong |
Targeted therapy drugs registered in Hong Kong are prescription only medicines and should be administered strictly under doctor’s instruction and recommendation. Examples of targeted therapy drugs registered in Hong Kong for the treatment of some cancer patients are listed below:
|
- Brain cancer: bevacizumab, everolimus
- Breast cancer: bevacizumab, everolimus, lapatinib, pertuzumab, trastuzumab and its antibody drug conjugates
- Colorectal cancer: aflibercept, bevacizumab, cetuximab, panitumumab, regorafenib
- Dermatofibrosarcoma protuberans: imatinib
- Gastric cancer: trastuzumab
- Gastrointestinal stromal tumour: imatinib, sunitinib
- Head and neck cancer: cetuximab
- Kidney cancer: axitinib, bevacizumab, everolimus, pazopanib, sorafenib, sunitinib, temsirolimus
- Leukaemia: dasatinib, imatinib, nilotinib, rituximab
- Liver cancer: sorafenib
- Lung cancer: afatinib, bevacizumab, crizotinib, erlotinib, gefitinib
- Lymphoma: bortezomib, brentuximab vedotin, ibritumomab tiuxetan, rituximab, temsirolimus
- Melanoma: dabrafenib, ipilimumab, vemurafenib
- Multiple myeloma: bortezomib, lenalidomide
- Myelodysplastic/myeloproliferative disorders: imatinib, ruxolitinib
- Ovarian epithelial/fallopian tube/primary peritoneal cancers: bevacizumab
- Pancreatic cancer: erlotinib, everolimus, sunitinib
- Soft tissue sarcoma: pazopanib
- Thyroid cancer: sorafenib, vandetanib
|
|
▲ back to top
Side effects of targeted therapy drugs
|
 |
Scientists had expected that targeted therapy drugs would be less toxic than traditional chemotherapy drugs. However, targeted therapy drugs can have substantial side effects.
Common side effects seen with targeted therapy drugs are nausea and vomiting, diarrhea, and liver problems such as hepatitis and elevated liver enzymes. Other side effects include: |
- Skin problems (e.g. acneiform rash, dry skin, nail changes, hair depigmentation)
- Problems with blood clotting and wound healing
- High blood pressure
- Heart damage
- Gastrointestinal perforation (a rare side effect of some targeted therapy drugs)
The severity of side effects can vary greatly from drug to drug and from person to person. Most side effects go away over time after treatment ends and the healthy cells recover. The time it takes to get over side effects varies from person to person. It depends on many factors, including your overall health and the drugs you were given.
Because many targeted therapy drugs are still quite new, it’s hard to say how long you can expect side effects to last. Some of the side effects from standard chemotherapy drugs can last a lifetime, such as when the drug causes long-term damage to the heart, lungs, kidneys, or reproductive organs. In many cases we still don’t know if targeted therapy drugs cause these kinds of long-term changes.
|
|
|
|
▲ back to top
General advice
|
-
When the prescribed targeted therapy drugs are tablets or capsules, you may take the drugs at home. You should take the exact dose, at the scheduled time, for as long as it has been prescribed.
- Intravenous drugs are usually given as an infusion that can last for 30 minutes to a few hours. The infusion might be done in a clinic or a hospital.
- The frequency and duration of your treatment depend on the kind of cancer you have, the goals of the treatment, the drugs being used, and how your body responds to them. You may get treatments daily, weekly, every few weeks, or even less often. Some drugs are given in on-and-off cycles to allow your body to build healthy new cells and regain its strength during the breaks. Other drugs may be taken every day for many months or even years.
- Cancer and its treatment can bring major changes to your life. You may feel sad, anxious, angry, depressed, and other feelings. To cope with the emotional changes, you may keep friends and family close, and find a good listener to talk with. You may also ask your doctor about counselors, groups, or networks where you can find support.
|
|
▲ back to top
Communication with your doctor
|
|
 |
|
- Ask your doctor about your cancer, including your treatment options. As you learn more about cancer, you may become more confident in making treatment decisions.
- Talk to your doctor about what possible side effects to expect from targeted therapy drugs, including how they will be treated if they do appear. Rare and unusual side effects can happen with some of these drugs, and some can be serious. All changes and side effects should be reported to your doctor.
|
- Always ask your doctor before taking any other medicines or health products as they may affect the efficacy or increase the side effects of your medication.
- Be sure to ask your doctor if you can drink beer, wine, or any other alcoholic beverages as alcohol may affect the efficacy or increase the side effects of your medication.
- The evidence on the effectiveness of alternative cancer treatments to cure cancer is not clear. But alternative treatment options (e.g. acupuncture, hypnosis, massage, meditation, relaxation techniques and yoga) may help you cope with side effects of cancer and cancer treatment, such as fatigue, nausea and pain. Talk to your doctor about what alternative treatment options may offer some benefit.
- You should talk to your doctor before taking targeted therapy drugs if you are pregnant or plan to become pregnant because targeted therapy drugs may cause birth defects.
|
|
|
|
▲ back to top
Storage targeted therapy drugs |
|
Targeted therapy drugs should be stored according to condition specified on the label, for oral targeted therapy drugs usually kept in a cool and dry place, whereas for injectable targeted therapy drugs usually store in refrigerators. Furthermore, drugs should be kept properly in places unreachable by children to prevent accidental ingestion.
|
|
▲ back to top
|
|
Acknowledgement: The Drug Office would like to thank the Professional Development and Quality Assurance (PD&QA) and Non-communicable Disease Division of Surveillance & Epidemiology Branch (NCDD of SEB) for their valuable contribution to the preparation of this article
|
|
|
|
|
Drug Office
Department of Health
Dec 2015
|
