Biological therapy

Biological therapy uses natural or artificial substances that act like (mimic) or block natural cell responses to kill, control or change the behaviour of cancer cells. It is also called biotherapy or biological response modifiers (BRMs).

Although biological therapies have been used for many years to treat other diseases, their use in treating cancer is still relatively new. Biological therapies are used to:

slow the growth, lessen the spread and lower the risk of recurrence (the cancer coming back) for some cancers
control symptoms of cancer
lessen some of the side effects from cancer treatments
treat a small number of cancers
deliver radioactive substances (radioactive isotopes) or chemotherapy drugs directly to a tumour

How biological therapy works

Biological therapy works by stimulating, boosting, restoring or acting like the body’s immune system response against cancer cells. Different types of biological therapies work in different ways.

Biological therapy is based on the theory that the immune system helps destroy cancer cells.

The immune system protects a person from infection and disease. Parts of the immune system recognize antigens on the surface of viruses, bacteria, other germs and cancer cells. Antigens mark these cells as being different (foreign) so the immune system can find them. The immune system reacts to these antigens and destroys the cells they are attached to.
Normal cells and cancer cells are very similar. This makes it difficult for the immune system to recognize cancer cells.
In some cases, the immune system may recognize cancer cells, but it may not be strong enough to kill them.

Types of biological therapy

A number of different biological therapies are used to treat certain types of cancer. Biological therapies can be confusing because they aren’t grouped in a simple, easy-to-follow way. Some biological drugs are grouped according to the effect they have, such as blocking cell growth. Others are grouped by a particular type of drug, and some drugs belong to more than one group.

Immunotherapy

Immunotherapy is a type of biological therapy that uses the immune system to help destroy cancer cells. Immunotherapy may be active or passive.

Active immunotherapy stimulates and strengthens the body’s immune system response so that it attacks and destroys cancer cells. It can be either non-specific or specific.
- Non-specific active immunotherapies (such as interferon and interleukin) stimulate or boost the immune system in a very general way.
- Specific active immunotherapies (such as cancer vaccines) use antigens of a specific type of cancer cell to trigger an immune response. They do not cause a general immune system response.
Passive immunotherapy uses substances that act like parts of the immune system and attack specific cells. These substances are made in a laboratory. Treatment using monoclonal antibodies is an example of passive immunotherapy.

Cytokines

Cytokines are naturally occurring chemicals made by different immune system cells. They are the messengers of the immune system. Cytokines allow immune system cells to communicate with each other and thus help carry out the immune system response.

Interferon is a type of cytokine that the body naturally makes in small amounts. It is also made in the laboratory so that it can be given in larger amounts to treat cancer. Interferon can improve the way the immune system acts against cancer cells. It also acts directly on cancer cells to slow their growth.
Interleukin is another cytokine that occurs naturally in the body and is also made in the laboratory. Interleuken-2 stimulates the growth and activity of certain immune cells that recognize and destroy cancer cells.
Tumour necrosis factor (TNF) is a cytokine produced by macrophages and lymphocytes (types of white blood cells that fight foreign cells). TNF stimulates the immune system to attack tumour cells and their blood vessels. Researchers are currently studying TNF in clinical trials.

Monoclonal antibodies

Monoclonal antibodies are made in the laboratory. They find and bind to a specific antigen on a cancer cell. Monoclonal antibodies may:

trigger the immune system to attack and kill cancer cells
stop cancer cells from using proteins they need to grow
be used to carry cancer drugs or radiation to cancer cells

Vaccines

Cancer vaccines work just like vaccines for other diseases, such as measles or chicken pox. They are injected after cancer is diagnosed. Vaccines may encourage the person’s immune system to identify cancer cells and stimulate T cells to attack them. For example, bacillus Calmette-Guérin (BCG) vaccine is used to treat bladder cancer. Cancer vaccines may also help prevent cancer from recurring (coming back).

Anti-angiogenesis drugs

Angiogenesis is the growth of new blood vessels. A tumour has to make new blood vessels to grow, but normal organs do not. Anti-angiogenesis drugs try to starve the tumour by stopping the development of new blood vessels.

Colony-stimulating factors

Colony-stimulating factors (CSFs) do not directly affect tumour cells. They stimulate the bone marrow to produce more red blood cells, white blood cells and platelets. CSFs are used to treat side effects of cancer treatments that may make someone more vulnerable to anemia, infection or bleeding.

Cancer growth inhibitors

Growth factors are naturally occurring chemicals that control cell growth. Cancer growth inhibitors block the growth factors that make cancer cells divide and grow. The different types of cancer growth inhibitors are named after the type of chemical they block. The main types are:

tyrosine kinase inhibitors
proteasome inhibitors
growth factor receptor inhibitors

Gene therapy

Researchers are actively studying gene therapy as a cancer treatment. This therapy introduces genetic material into a person’s cells to repair a mutation. Researchers are looking at ways of using gene therapy to change a person with cancer’s genetic material to fight or prevent disease.

For more detailed information on specific drugs, go to sources of drug information.

Getting biological therapy

The type of biological therapy used depends on the type and stage of cancer. Each type works differently to stimulate or strengthen the immune system. Biological therapy may be used alone or it may be combined with other cancer treatments, such as surgery, chemotherapy or radiation therapy.

Getting biological therapy includes assessment before treatment, having the treatment and follow-up after treatment is finished.

Biological therapy for children

When children are diagnosed with cancer, both children and their families have questions and concerns about biological therapy. They want to know how it is given and how to manage the treatment. Being prepared and knowing what to expect can reduce anxiety for both children and parents. Parents and caregivers can prepare and help children cope with biological therapy by giving them explanations that are appropriate to their age and maturity.

Side effects of biological therapy

Biological therapy travels through the entire body, so side effects affect the whole body as well. How bad side effects are depends on the type of biological therapy, the dose of the drug, how the drug is given and the schedule for taking the drug. Most side effects of biological therapy can be treated with other drugs. Side effects will improve once biological therapy is finished.

References

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