Anti-Angiogenic Therapy: Pros And Cons For Cancer Treatment

Anti-angiogenic therapy is a new type of targeted anti-cancer therapy. It involves the use of a new class of drugs that controls blood vessel growth to restore the health. The growing tumors need their own blood supply to enlarge and thrive. Blood vessels deliver oxygen and nutrients to the tumor, and cutting off the vasculature of the tumor literally starves the tumor of the vital supplies thus preventing its further growth and spreading.

The results can be more impressive when anti-angiogenic drugs are combined with other approaches to eliminate the tumors.

This type of therapy was first proposed in 1971, and it became a recognized method of cancer growth prevention in 1976. But the idea was very slow to develop, and only recently the drugs from this class have reached the hospitals. There are different types of anti-angiogenic therapy and the different drugs work in different ways to block the growth of blood vessels.

Why is Angiogenesis Important in Cancer?

Angiogenesis is a term that describes the formation of new blood vessels. It involves the growth, migration and differentiation of endothelial cell, the cells that form the lining of the internal walls of blood vessels. Specific chemical signals in the body control this process and the signals can either stimulate the new blood vessel formation and the repair of blood vessels that are damaged. Other chemical signal referred to as angiogenesis inhibitors interfere with the formation of blood vessels. Under normal circumstances, there is a balance between both of these signals so that blood vessels only start to form when they are needed.

For a tumor to get larger than a few millimeters, it must have its own blood supply. The chemical signals that stimulate blood vessel formation are responsible for the creation of tumor blood vessels. Tumors may also stimulate angiogenesis by giving off these chemical signals, thus stimulating the local blood vessels formation.

Both synthetic and natural angiogenesis inhibitors are being created in the laboratories around the world with the hope that these drugs will slow the growth of cancer, or completely prevent it from developing.

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Types of Anti-Angiogenesis Treatment

There are three primary types of anti-angiogenesis treatment that can be considered for cancer patients. These include:

• Blocking blood vessel growth factor: Some drugs in this class work by blocking the vascular endothelial growth factor from being able to attach itself to the cell receptors lining the blood vessels. This prevents the blood vessel growth.
• Blocking signaling within the cells: The drugs in this class work by stopping the vascular endothelial growth factor receptors from transmitting the growth signals to the cells of blood vessels. These drugs are also called tyrosine kinase inhibitors or cancer growth blockers.
• Affecting the signaling between the cells: The drugs from this class work on the level of chemical signals that the cells rely on to stimulate the other cells to grow.

Arguments For And Against Anti-Angiogenic Therapy

Pros of Anti-Angiogenic Therapy

Compared to traditional cancer therapies, anti-angiogenic therapy offers a variety of advantages, including:

• Tumor cells can mutate and start to resist chemotherapy. Anti-angiogenic cells target only endothelial cells and these cells are far less likely to become resistant to drugs.
• Conventional radiation and chemotherapy attack all of the cells that are dividing in the body. This can lead to unpleasant side effects, such as diarrhea, hair loss, ulcers in the mouth and weakened immunity. Anti-angiogenic therapy medications selectively target the blood vessels that are dividing, resulting in fewer side effects.
• This therapy allows continuous and more predictable control of a disease.
• Host blood vessels are necessary for all tumors to grow and thrive. This therapy does not target a specific type of cancer cell, but the blood vessels feeding the tumors, making it a therapy that can be used for a broad range of cancers.
• The drugs used in anti-angiogenic therapy are relatively nontoxic, especially compared to the traditional chemotherapy and other drugs used for cancer. They are able to be effective at doses far below the maximum tolerated dose. This means that patients can receive the drugs over a longer period of time, at lower doses, thus creating the potential for more successful treatment.
• Anti-angiogenic drugs can work along with radiation and chemotherapy when necessary without interfering with the other therapy's positive effects.
• These drugs are quick and easy to administer and require little to no preparation. The oral drugs are taken with a full glass of water and the injected drugs simply require the injection site to be swabbed with alcohol prior to inserting the needle.
• These drugs require no aftercare after being administered.
• Doctors and scientists can determine the best biologic dose of these drugs through measuring the peripheral blood cells. This is relatively simple, ensuring the best dose for the patient.

Cons of Anti-Angiogenic Therapy

As with all medical treatments, there are disadvantages that have to be considered when looking at the overall benefits of the therapy.

Their experimental nature makes it difficult for those that may benefit from the drugs to get access to them.

Avastin is a drug approved by the FDA that is an anti-angiogenic therapy and it is used for colorectal cancer, non-small cell lung cancer and kidney cancer. This drug, unfortunately, presents the risk for very serious side effects, including:

• Intestinal perforation
• The opening up of stitched wounds
• Coughing up mucous containing blood or just blood
• Severe bleeding in tumors
• Potentially dangerous effects on a developing fetus

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Right now the potential is there, but a lot more research is necessary before this form of cancer therapy can be considered on a broad stage.

Anti-angiogenic therapy has a long way to go since many drugs are still in the clinical trial phase. However, if scientists can achieve the results they are seeking, this has a potential to creates a whole new frontier in cancer treatment. Since anti-angiogenic treatment is specific to stopping tumors from getting the blood vessels they need for nutrients and oxygen supply, this could work to treat a wide array of cancers.