April
29, 2003
Choi, Sarah
Kim, Jin
WHAT IS LUNG CANCER?
Lung
cancer is the leading cancer killer in both men and women. There were an estimated
164,100 new cases of lung cancer and an estimated 156,900 deaths from lung cancer
in the United States in 2000.
The
rate of lung cancer cases appears to be dropping among white and
African-American men in the United States, while it continues to rise among
both white and African-American women.
There
are two major types of lung cancer: non-small cell lung cancer and small
cell lung cancer. Non-small cell lung cancer is much more common. It
usually spreads to different parts of the body more slowly than small cell lung
cancer. Squamous cell carcinoma, ademocarcinoma, and large cell carcinoma are
three types of non-small cell lung cancer. Small cell lung cancer also called
oat cell cancer, accounts for about 20% of all lung cancer.
WHAT CAUSES LUNG CANCER?
Smoking
is the number one cause of lung cancer. Lung cancer may also be the most tragic
cancer because in most cases, it might have been prevented -- smoking causes
87% of lung cancer cases. Cigarette smoke contains more than 4,000 different
chemicals, many of which are proven cancer-causing substances, or carcinogens.
Smoking cigars or pipes also increases the risk of lung cancer.
The
more you smoke and the longer you smoke, the greater your risk of lung cancer.
But if you stop smoking, the risk of lung cancer decreases each year as normal
cells replace abnormal cells. After ten years, the risk drops to a level that
is one-third to one-half of the risk for people who continue to smoke. In
addition, quitting smoking greatly reduces the risk of developing other
smoking-related diseases, such as heart disease, stroke, emphysema and chronic
bronchitis.
Many
of the chemicals in tobacco smoke also affect the nonsmoker inhaling the smoke,
making "secondhand smoking" another important cause of lung cancer.
It is responsible for approximately 3,000 lung cancer deaths and as many as
62,000 deaths from heart disease annually.
Radon
is considered to be the second leading cause of lung cancer in the U.S. today.
Radon gas can come up through the soil under a home or building and enter
through gaps and cracks in the foundation or insulation, as well as through
pipes, drains, walls or other openings. Radon causes between 15,000 and 22,000
lung cancer deaths each year in the United States -- 12 percent of all lung
cancer deaths are linked to radon.
Radon
problems have been found in every state. The EPA estimates that nearly 1 out of
every 15 homes in the U.S. has indoor radon levels at or above the level at
which homeowners should take action -- 4 picocuries per liter of air (pCi/L) on
a yearly average. Radon can be a problem in schools and workplaces, too.
Because
you cannot see or smell radon, the only way to tell if you are being exposed to
the gas is by measuring radon levels. Exposure to radon in combination with
cigarette smoking greatly increases the risk of lung cancer. That means for
smokers, exposure to radon is an even greater health risk.
Another
leading cause of lung cancer is on-the-job exposure to cancer-causing
substances or carcinogens. Asbestos is a well-known, work-related substance
that can cause lung cancer, but there are many others, including uranium,
arsenic, and certain petroleum products.
There
are many different jobs that may involve exposure. Some examples are working
with certain types of insulation, working in coke ovens, and repairing brakes.
When exposure to job-related carcinogens is combined with smoking, the risk of
getting lung cancer is sharply increased.
Lung
cancer takes many years to develop. But changes in the lung can begin almost as
soon as a person is exposed to cancer-causing substances. Soon after exposure
begins, a few abnormal cells may appear in the lining of the bronchi (the main
breathing tubes). If a person continues to be exposed to the cancer-causing
substance, more abnormal cells will appear. These cells may be on their way to
becoming cancerous and forming a tumor.
HOW IS LUNG CANCER DETECTED?
In its
early stages, lung cancer usually does not cause symptoms. When symptoms occur,
the cancer is often advanced. Symptoms of lung cancer include:
• Chronic cough
• Hoarseness
• Coughing up blood
• Weight loss & loss of appetite
• Shortness of breath
• Fever without a known reason
• Wheezing
• Repeated bouts of bronchitis or
pneumonia
• Chest pain
These conditions are also symptomatic of
many other lung problems, so a person who has any of these symptoms should see
a doctor to find out the cause.
When a person goes for an exam, the
doctor ask many questions about the person's medical history, including
questions about the patient's exposure to hazardous substances. The doctor will
also give the patient a physical exam. If the patient has a cough that produces
a sputum (mucus), it may be examined for cancer cells.
The doctor will order a chest X-ray or
specialized X-ray such as the CT scan, which help to locate any abnormal spots
in the lungs. The doctor may insert a small tube called a bronchoscope through
the nose or mouth and down the throat, to look inside the airways and lungs and
take a sample, or biopsy, of the tumor. This is just one of several ways in
which a doctor may take a biopsy sample.
A growing number of doctors are using a
form of CT scan in smokers to spot small lung cancers, which are more likely
than large tumors to be cured. The technique, called helical low-dose CT scan,
is much more sensitive than a regular X-ray and can detect tumors when they are
small.
More studies on this type of screening
will show whether routine screening of smokers and others at risk for lung
cancer will save lives.
If you are diagnosed with cancer, the
doctor will do testing to find out whether the cancer has spread, and, if so,
to which parts of the body. This information will help the doctor plan the most
effective treatment. Tests to find out whether the cancer has spread can
include a CT scan, an MRI, or a bone scan.
HOW
IS LUNG CANCER TREATED?
The doctor will decide which treatment
you will receive based on factors such as the type of lung cancer, the size,
location and extent of the tumor (whether or not it has spread), and your
general health. There are many treatments, which may be used alone or in
combination. These include:
SURGERY may cure lung cancer. It is used in
limited stages of the disease. The type of surgery depends on where the tumor
is located in the lung. Some tumors cannot be removed because of their size or
location.
RADIATION THERAPY is a form of
high energy X-ray that kills cancer cells. It is used:
• In combination with chemotherapy and
sometimes with surgery.
• To offer relief from pain or blockage
of the airways.
CHEMOTHERAPY is the use of
drugs that are effective against cancer cells. Chemotherapy may be injected
directly into a vein or given through a catheter, which is a thin tube that is
placed into a large vein and kept there until it is no longer needed. Some
chemotherapy drugs are taken by pill. Chemotherapy may be used:
• In conjunction with surgery.
• In more advanced stages of the disease
to relieve symptoms.
• In all stages of small cell cancer.
Cancer of the lung and bronchus
(hereafter, lung cancer) is the second most common cancer among both men and women
and is the leading cause of cancer death in both sexes. Among men, age-adjusted
lung cancer incidence rates (per 100,000) range from a low of about 14 among
American Indians to a high of 117 among blacks, an eight- fold difference.
Between these two extremes, rates fall into two groups ranging from 42 to 53
for Hispanics, Japanese, Chinese, Filipinos, and Koreans and from 71 to 89 for
Vietnamese, whites, Alaska Natives and Hawaiians. The range among women is much
narrower, from a rate of about 15 among Japanese to nearly 51 among Alaska
Natives, only a three-fold difference. Rates for the remaining female
populations fall roughly into two groups with low rates of 16 to 25 for Korean,
Filipino, Hispanic and Chinese women, and rates of 31 to 44 among Vietnamese,
white, Hawaiian and black women. The rates among men are about two to three
times greater than the rates among women in each of the racial/ethnic groups.
In the 30-54 year age group,
incidence rates among men are double those among women in most of the
racial/ethnic groups. In white non-Hispanics and white Hispanics, however
incidence rates for women are closer to those for men. This suggests that
smoking cessation and prevention programs may have been especially successful
among white men and/or that such programs have not been as effective among
white women.
Age-adjusted mortality rates
follow similar racial/ethnic patterns to those for the incidence rates. Among
men, the incidence and mortality rates are very similar. Filipino men are an
exception, with an incidence rate nearly twice as large as their mortality
rate. Incidence rates are also similar to mortality rates among women, with the
exception of Filipinos and Hispanics. In these two groups, incidence rates are
nearly twice as large as mortality rates. Among Hawaiian women, the mortality
rate actually exceeds the incidence rate. This may be due to differences in the
accuracy of race classification on medical records versus death certificates.
Racial/ethnic patterns are
generally consistent within each age group for both incidence and mortality. An
exception is the high incidence and mortality rate in Chinese women aged 70
years and older. This group tends to have low incidence and mortality rates in
the younger age groups.
Cigarette smoking accounts for
nearly 90% of all lung cancers. Passive smoking also contributes to the
development of lung cancer among nonsmokers. Certain occupational exposures
such as asbestos exposure are also known to cause lung cancer. Air pollution is
a probable cause, but makes a relatively small contribution to incidence and
mortality rates. In certain geographic areas of the United States, indoor
exposure to radon may also make a small contribution to the total incidence of
lung cancer.
The graph above shows figures for
males (green squares) and females (purple diamonds). It shows a substantial
decrease in new cases of lung cancer in men, and a slight increase in women.
This reflects a large decrease in smoking by men since the 1940s, and a slight
(and later) increase in smoking by women.
Bibliography
- www.offsonline.com
- Source: Miller BA, Kolonel LN, Bernstein L,
Young, Jr. JL, Swanson GM, West D, Key CR, Liff JM, Glover CS, Alexander GA, et
al. (eds). Racial/Ethnic Patterns of Cancer in the United States 1988-1992,
National Cancer Institute. NIH Pub. No. 96-4104. Bethesda, MD, 1996.
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Graphs showing incidence and mortality
for specific racial and ethnic groups including information that may not be
discussed in the text above, is available at the NCI's Surveillance,
Epidemiology, and End Results (SEER) Web site at: http://seer.cancer.gov/.
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