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.
2.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.
3.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.
4.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.
5.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.
6.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.
7.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.
8.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.
9.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.
People interested in taking part in a clinical trial
should talk with their doctor. Information about
clinical trials is available from the Cancer Information
Service (CIS) (see below) at 1–800–4–CANCER. Information
specialists at the CIS use PDQ®, NCI’s cancer
information database, to identify and provide detailed
information about specific ongoing clinical trials.
Patients also have the option of searching for clinical
trials on their own. The clinical trials page on the
NCI’s Cancer.gov Web site, located at http://www.cancer.gov/clinical_trials
on the Internet, provides general information about
clinical trials and links to PDQ.
People considering clinical trials may be interested in
the NCI booklet Taking Part in Clinical Trials: What
Cancer Patients Need To Know. This booklet describes how
research studies are carried out and explains their
possible benefits and risks. The booklet is available by
calling the CIS, or from the NCI Publications Locator
Web site at http://www.cancer.gov/publications on the
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