Saturday, February 9, 2013

What’s new in malignant mesothelioma research and treatment?

What’s new in malignant mesothelioma
research and treatment?
There is always research going on in the area of mesothelioma. Scientists are looking for
ways to prevent, diagnose, and treat mesothelioma. Despite recent progress, much
remains to be learned about the best way to treat these cancers.
Causes and prevention
Much of the research on mesothelioma has focused on learning exactly how asbestos
changes mesothelial cells and their DNA to cause these cancers. Understanding how
these fibers produce cancer might help us develop ways to prevent those changes.
The role of asbestos in increasing the risk of mesothelioma is a definite public health
concern. Researchers are learning more about which fibers can produce cancer, how they
cause these cancers, and what levels of exposure can be considered safe. Now that the
dangers of asbestos are known, we can limit or stop exposure in homes, public buildings,
and the workplace. Unfortunately, regulations protecting workers from asbestos exposure
are much less stringent in some countries than in others.
Research is also under way to clarify the role (if any) of SV40, a virus that has been
linked to mesothelioma in some studies.
Genetics
Researchers are starting to understand how certain changes in DNA can cause normal
cells to become mesothelioma cells. DNA is the substance in our cells that carries the
instructions for nearly everything they do.
Some genes (parts of our DNA) contain instructions for controlling when our cells grow
and divide into new cells. Certain genes that cause cells to grow and divide are called
oncogenes. Others that slow down cell division or cause cells to die at the right time are
called tumor suppressor genes. Cancers can be caused by DNA changes that turn on
oncogenes or turn off tumor suppressor genes.

Researchers have found some of the important DNA changes in mesothelioma cells in
recent years. Continued research in understanding these changes may lead to new tests
for earlier diagnosis and new drugs for more effective treatment.
Treatment
Mesothelioma remains a difficult cancer to treat, and doctors are constantly trying to
improve on current approaches. The exact roles of surgery, radiation therapy, and
chemotherapy in the treatment of mesothelioma are highly debated. Combinations of
these treatments, called multimodality therapy, are now being tested and may provide the
most promising option for some patients. Newer types of treatment now being studied
may give patients and their doctors even more options.
Chemotherapy
Some chemotherapy drugs can shrink or slow the growth of mesotheliomas, but in most
cases the effects last for a limited time. Several newer chemotherapy drugs, including
raltitrexed, are now being tested in clinical trials, often together with other types of
treatment.
As mentioned in the section “Chemotherapy for malignant mesothelioma,” doctors are
exploring giving chemotherapy drugs directly into the chest or abdomen, often right after
surgery. In some cases the drugs are heated before they are given. Doctors hope that
putting the drugs directly into contact with the tumors may help them work better, while
limiting the side effects in the rest of the body.
Photodynamic therapy
Another technique now being studied is photodynamic therapy (PDT). For this treatment,
a light-activated drug is injected into a vein. The drug spreads throughout the body and
tends to collect in cancer cells. A few days later (usually just after surgery for the
mesothelioma), a special red light on the end of a tube is placed into the chest cavity. The
light causes a chemical change that activates the drug and causes the cancer cells to die.
Since the drug is only active in the areas exposed to the special light, this approach may
cause fewer side effects than use of drugs that spread throughout all tissues of the body.
Several clinical trials are now studying the use of PDT for mesothelioma.
Targeted drugs
In general, chemotherapy drugs are limited in their effectiveness against mesothelioma.
As researchers have learned more about the changes in cells that cause cancer, they have
been able to develop newer drugs that specifically target these changes. Targeted drugs
work differently from standard chemotherapy drugs. They may sometimes work when
chemotherapy drugs do not, and they often have different (and less severe) side effects.
One group of targeted drugs is known as angiogenesis inhibitors. These drugs slow the
growth of new blood vessels (angiogenesis), which tumors need to grow larger. Some of

these drugs are already used to treat other types of cancer and are now being studied for
use against mesotheliomas. Examples of these drugs include bevacizumab (Avastin
®
) and
sorafenib (Nexavar
®
).
Other new drugs have different targets. For example, some new drugs target mesothelin,
a protein found in high levels in mesothelioma cells.
Other targeted drugs are already used to treat other types of cancer and are now being
tested in mesothelioma clinical trials, including imatinib (Gleevec
®
), dasatinib
(Sprycel
®
), bortezomib (Velcade
®
), and vorinostat (Zolinza
®
).
Newer forms of treatment
Because standard treatments often have limited usefulness against mesothelioma,
researchers are studying other new types of treatment as well.
A newer type of treatment being tested on mesothelioma is gene therapy, which attempts
to add new genes to cancer cells to make them easier to kill. One approach to gene
therapy uses special viruses that have been modified in the lab. The virus is injected into
the pleural space and infects the mesothelioma cells. When this infection occurs, the virus
injects the desired gene into the cells. In one version of this approach, the virus carries a
gene that helps turn on the immune system to attack the cancer cells. Early studies of this
approach have found it may shrink or slow the growth of mesothelioma in some people,
but more research is needed to confirm this.
Other new treatments called cancer vaccines are also aimed at getting the immune system
to attack the cancer. In one approach, immune cells are removed from a patient’s blood
and treated in the lab to get them to react to tumor cells. The immune cells are then given
back to the patient as blood transfusions, where it is hoped they will cause the body’s
immune system to attack the cancer. This approach is now being studied in clinical trials.


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