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.
1. 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://cancer.gov/clinical_trials on the Internet, provides general
information about clinical trials and links to PDQ.
Source: National Cancer Institute |
