Mesothelioma: Questions and Answers
Mesothelioma: Questions and Answers
Mesothelioma is a rare form of cancer in which malignant
(cancerous) cells are found in the mesothelium, a protective sac that
covers most of the body’s internal organs. Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles.
What is the mesothelium?
The mesothelium is a membrane that covers and protects most of the
internal organs of the body. It is composed of two layers of cells: One
layer immediately surrounds the organ; the other forms a sac around it.
The mesothelium produces a lubricating fluid that is released between
these layers, allowing moving organs (such as the beating heart and the
expanding and contracting lungs) to glide easily against adjacent
structures.
The mesothelium has different names, depending on its location in
the body. The peritoneum is the mesothelial tissue that covers most of
the organs in the abdominal cavity. The pleura is the membrane that
surrounds the lungs and lines the wall of the chest cavity. The
pericardium covers and protects the heart. The mesothelial tissue
surrounding the male internal reproductive organs is called the tunica
vaginalis testis. The tunica serosa uteri covers the internal
reproductive organs in women.
What is mesothelioma?
Mesothelioma (cancer of the mesothelium) is a disease in
which cells of the mesothelium become abnormal and divide without
control or order. They can invade and damage nearby tissues and organs.
Cancer cells can also metastasize (spread) from their original site to
other parts of the body. Most cases of mesothelioma begin in the pleura
or peritoneum.
How common is mesothelioma?
Although reported incidence rates have increased in the past 20 years, mesothelioma
is still a relatively rare cancer. About 2,000 new cases of
mesothelioma are diagnosed in the United States each year. Mesothelioma
occurs more often in men than in women and risk increases with age, but
this disease can appear in either men or women at any age.
What are the risk factors for mesothelioma?
Working with asbestos is the major risk factor for mesothelioma. A
history of asbestos exposure at work is reported in about 70 percent to
80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.
Asbestos is the name of a group of minerals that occur naturally as
masses of strong, flexible fibers that can be separated into thin
threads and woven. Asbestos has been widely used in many industrial
products, including cement, brake linings, roof shingles, flooring
products, textiles, and insulation. If tiny asbestos particles float in
the air, especially during the manufacturing process, they may be
inhaled or swallowed, and can cause serious health problems. In addition
to mesothelioma, exposure to asbestos increases the risk of lung
cancer, asbestosis (a noncancerous, chronic lung ailment), and other
cancers, such as those of the larynx and kidney.
Smoking does not appear to increase the risk of mesothelioma.
However, the combination of smoking and asbestos exposure significantly
increases a person’s risk of developing cancer of the air passageways in
the lung.
Who is at increased risk for developing mesothelioma?
Asbestos has been mined and used commercially since the late 1800s.
Its use greatly increased during World War II. Since the early 1940s,
millions of American workers have been exposed to asbestos dust.
Initially, the risks associated with asbestos exposure were not known.
However, an increased risk of developing mesothelioma was later
found among shipyard workers, people who work in asbestos mines and
mills, producers of asbestos products, workers in the heating and
construction industries, and other tradespeople. Today, the U.S.
Occupational Safety and Health Administration (OSHA) sets limits for
acceptable levels of asbestos exposure in the workplace. People who work
with asbestos wear personal protective equipment to lower their risk of
exposure.
The risk of asbestos-related disease increases with heavier
exposure to asbestos and longer exposure time. However, some individuals
with only brief exposures have developed mesothelioma. On the other hand, not all workers who are heavily exposed develop asbestos-related diseases.
There is some evidence that family members and others living with asbestos workers have an increased risk of developing mesothelioma,
and possibly other asbestos-related diseases. This risk may be the
result of exposure to asbestos dust brought home on the clothing and
hair of asbestos workers. To reduce the chance of exposing family
members to asbestos fibers, asbestos workers are usually required to
shower and change their clothing before leaving the workplace.
What are the symptoms of mesothelioma?
Symptoms of mesothelioma may not appear until 30 to 50 years
after exposure to asbestos. Shortness of breath and pain in the chest
due to an accumulation of fluid in the pleura are often symptoms of
pleural mesothelioma. Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a buildup of fluid in the abdomen. Other symptoms of peritoneal mesothelioma
may include bowel obstruction, blood clotting abnormalities, anemia,
and fever. If the cancer has spread beyond the mesothelium to other
parts of the body, symptoms may include pain, trouble swallowing, or
swelling of the neck or face.
These symptoms may be caused by mesothelioma or by other,
less serious conditions. It is important to see a doctor about any of
these symptoms. Only a doctor can make a diagnosis.
How is mesothelioma diagnosed?
Diagnosing mesothelioma is often difficult, because the
symptoms are similar to those of a number of other conditions. Diagnosis
begins with a review of the patient’s medical history, including any
history of asbestos exposure. A complete physical examination may be
performed, including x-rays of the chest or abdomen and lung function
tests. A CT (or CAT) scan or an MRI may also be useful. A CT scan is a
series of detailed pictures of areas inside the body created by a
computer linked to an x-ray machine. In an MRI, a powerful magnet linked
to a computer is used to make detailed pictures of areas inside the
body. These pictures are viewed on a monitor and can also be printed.
A biopsy is needed to confirm a diagnosis of mesothelioma.
In a biopsy, a surgeon or a medical oncologist (a doctor who specializes
in diagnosing and treating cancer) removes a sample of tissue for
examination under a microscope by a pathologist. A biopsy may be done in
different ways, depending on where the abnormal area is located. If the
cancer is in the chest, the doctor may perform a thoracoscopy. In this
procedure, the doctor makes a small cut through the chest wall and puts a
thin, lighted tube called a thoracoscope into the chest between two
ribs. Thoracoscopy allows the doctor to look inside the chest and obtain
tissue samples. If the cancer is in the abdomen, the doctor may perform
a peritoneoscopy. To obtain tissue for examination, the doctor makes a
small opening in the abdomen and inserts a special instrument called a
peritoneoscope into the abdominal cavity. If these procedures do not
yield enough tissue, more extensive diagnostic surgery may be necessary.
If the diagnosis is mesothelioma, the doctor will want to
learn the stage (or extent) of the disease. Staging involves more tests
in a careful attempt to find out whether the cancer has spread and, if
so, to which parts of the body. Knowing the stage of the disease helps
the doctor plan treatment.
Mesothelioma is described as localized if the cancer is
found only on the membrane surface where it originated. It is classified
as advanced if it has spread beyond the original membrane surface to
other parts of the body, such as the lymph nodes, lungs, chest wall, or
abdominal organs.
How is mesothelioma treated?
Treatment for mesothelioma depends on the location of the
cancer, the stage of the disease, and the patient’s age and general
health. Standard treatment options include surgery, radiation therapy,
and chemotherapy. Sometimes, these treatments are combined.
Surgery is a common treatment for mesothelioma. The doctor
may remove part of the lining of the chest or abdomen and some of the
tissue around it. For cancer of the pleura (pleural mesothelioma),
a lung may be removed in an operation called a pneumonectomy. Sometimes
part of the diaphragm, the muscle below the lungs that helps with
breathing, is also removed.
Radiation therapy, also called radiotherapy, involves the use of
high-energy rays to kill cancer cells and shrink tumors. Radiation
therapy affects the cancer cells only in the treated area. The radiation
may come from a machine (external radiation) or from putting materials
that produce radiation through thin plastic tubes into the area where
the cancer cells are found (internal radiation therapy).
Chemotherapy is the use of anticancer drugs to kill cancer cells throughout the body. Most drugs used to treat mesothelioma
are given by injection into a vein (intravenous, or IV). Doctors are
also studying the effectiveness of putting chemotherapy directly into
the chest or abdomen (intracavitary chemotherapy).
To relieve symptoms and control pain, the doctor may use a needle
or a thin tube to drain fluid that has built up in the chest or abdomen.
The procedure for removing fluid from the chest is called
thoracentesis. Removal of fluid from the abdomen is called paracentesis.
Drugs may be given through a tube in the chest to prevent more fluid
from accumulating. Radiation therapy and surgery may also be helpful in
relieving symptoms.
Are new treatments for mesothelioma being studied?
Yes. Because mesothelioma is very hard to control, the
National Cancer Institute (NCI) is sponsoring clinical trials (research
studies with people) that are designed to find new treatments and better
ways to use current treatments. Before any new treatment can be
recommended for general use, doctors conduct clinical trials to find out
whether the treatment is safe for patients and effective against the
disease. Participation in clinical trials is an important treatment
option for many patients with mesothelioma.
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