Targeting Cancer Treatment - Specific Factors Of A Patient's Tumor

Editor's Choice
Main Category: Cancer / Oncology
Article Date: 03 Jun 2011 - 16:00 PDT

email to a friend   printer friendly   opinions  

Cancer treatment is depending more and more today on specific factors of a patient's tumor, including gene mutations, or proteins that are commonly typical of certain cancer cells, rather than focusing on where in the body the cancer started. Before, treatment was based on finding where in the body the cancer originated, such as the breast or lung.

Targeted therapy is all about the cancer's genes, tissue environment that contributes the tumor's growth and survival, and its proteins. Nowadays, cancer therapy is designed to interfere with a signal that tells the cancer cells not to die or tells it to divide, while before, chemotherapies had the goal of interfering with cancer cells as division was already underway, when the cells were dividing into new ones.

The human body is made of various types of cells, including skin cells, brain cells, or blood cells. Each one has a specific function.

Cancer occurs when healthy cells change and start growing out of control; they eventually form a tumor - a mass. A benign tumor is noncancerous, whereas a malignant one is cancerous, it can spread to other parts of the body.

Cancer cells either divide too quickly or do not die when they should do

Specific genetic mutations within a cell change the way it behaves.

• When the genes that control cell division mutate (change), they can multiply too quickly; the cell has become cancerous.
• Cells are genetically programmed to die, when the specific genes that tell the cell to die mutate, and the cell does not die, it has become a cancerous cell.

Put simply, cancerous cells either divide too rapidly or do not die when they should, in both cases because their genes have changed.

Researchers study cancer cells and how they respond to their environment; by doing this they are finding that particular gene mutations are linked to the development of certain cancers. They are then able to develop medications that modify the alterations that had occurred in the cancer cell to stop the erroneous instructions of either dividing too fast or not dying - the effect can be to destroy the tumor, or at least to slow down its progression.

One example is a type of breast cancer that has too much HER2 (human epidermal growth factor receptor 2), a type of protein. The drug Herceptin (trastuzumab) blocks HER2. 25% of breast cancers are of this type. Herceptin only works for this specific type of breast cancer.

A tumor is part of a network of blood vessels, lymph and tissues. Without this network the tumor would not exist. Cancer spreads when a bit breaks off from the tumor and travels through the bloodstream or lymph system. Blood vessels nearby help feed the growing tumor.

Targeting the new blood vessel growth around a tumor is an effective way of treating some cancers. The process of growing new blood cells is known as angiogenesis. Bevacizumab (Avastin), sunitinib (Sutent), sorafenib (Nexavar), lenalidomide (Revlimid), and thalidomide (Thalomid) are drugs that interfere with angiogenesis - they stop blood vessels being formed and growing around the tumor.

Targeted therapies can be classified as:

• Monoclonal antibodies - these are designed to block a specific target on the outside of cancer cells. A bit like trying to prevent electricity from flowing by placing a plastic plug into an electrical socket. As they are generally made up of large compounds which the body cannot absorb very well, they are administered intravenously. Examples include pertuzumab (Omnitarg), alemtuzumab (Campath-1H), panitumumab (Vectibix), bevacizumab, cetuximab (Erbitux), rituximab (Rituxan), and trastuzumab.
• Oral small molecules - the patient swallows a pill, as the molecules are much smaller than those in monoclonal antibodies the body can absorb them well. This type of medication usually interferes with cancer processes within the cancer cell, inside it. Examples include nilotinib (Tasigna), lapatinib (Tykerb), imatinib (Gleevec), sorafenib, dasatinib (Sprycel), erlotinib (Tarceva), gefitinib (Iressa), sunitinib, and temsirolimus (Torisel).
• Proteasome inhibitors - these are specialized proteins that interfere with enzymes (proteasomes) that break down other proteins within the cell when they are no longer needed. Bortezomib (Velcade), an injection that is used for treating multiple myeloma is an example.

Not all tumors have the same targets, though, recent studies have shown. A targeted treatment might not work for each patient. As these treatments may have side effects, and can be very costly, doctors have to try hard to match each patient to the most effective treatment whenever possible.

Sometimes targeting a medication to a tumor is not as simple as it sounds. What was targeted might turn out to be of no importance, or what worked before has no effect after a while - the cancer becomes resistant to the treatment. Targeted therapies may have serious side effects. Angiogenesis inhibitors are frequently linked to hypertension (high blood pressure).

Scientists and oncologists see targeted treatments as a major breakthrough in medicine. However, except in very few cases, these medications are not used on their own. Patients usually also undergo a combination of chemotherapy, radiation therapy, hormonal therapy or surgery.



Source: American Society of Clinical Oncology (ASCO)

Written by Christian Nordqvist


Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

• Additional
• References
• Citations