Lung Cancer
Risk
factors
Smoking
remains the greatest risk factor for lung cancer, accounting
for as many as 9 out of every 10 cases of the disease. Your
risk increases with the number of cigarettes you smoke each
day and the number of years you have smoked. Your risk is
also greater if you start smoking early in life — even if
you later quit. Smoking filtered, low-tar or low-nicotine
tobacco offers no additional protection because most people
who smoke these cigarettes inhale more deeply, which also
increases the risk.
On
the other hand, quitting — at any age — can significantly
lower your risk of developing lung cancer. After 10 years
of not smoking, your risk of lung cancer is reduced by one-third.
Cutting the number of cigarettes you smoke may also reduce
your risk, though not as dramatically as quitting completely.
Other
risk factors include:
* Your sex. Current or former women smokers are at greater
risk of lung cancer than are men who have smoked an equal
amount. Although the exact reasons for this are unknown,
some experts speculate that women may have a greater susceptibility
to the cancer-causing substances found in tobacco. Others
believe that estrogen may play a role. Women also are known
to inhale more than men do, and they are less likely to
quit.
* Exposure to secondhand smoke. Even if you don't smoke
yourself, you're at high risk of lung cancer if you're exposed
to the smoke of others. Daily exposure to secondhand smoke
may increase your chances of developing lung cancer.
* Exposure to radon gas. Second only to smoking as a cause
of lung cancer, radon comes from the natural (radioactive)
breakdown of uranium in soil, rock and water that eventually
becomes part of the air you breathe. Although unsafe levels
of radon can accumulate in any building, the greatest exposure
risk most people face is at home. The Surgeon General and
the Environmental Protection Agency recommend that all homeowners
check for the presence of radon. The best tests are those
that take three to six months. For more information, contact
your county public health department or visit the Environmental
Protection Agency Web site.
* Exposure to asbestos and other chemicals. Workplace exposure
to asbestos and other cancer-causing agents — such as vinyl
chloride, nickel chromates and coal products — also can
increase your risk of developing lung cancer, especially
if you're a smoker.
* Race. Black Americans are at a higher risk of lung cancer.
They also develop the disease at an earlier age and are
less likely to survive. Doctors don't think there's a genetic
reason for this disparity. Rather, it is more likely to
be related to inequities in health care and to environmental
factors.
* Heredity. Research increasingly points to a genetic factor
in lung cancer. Although smoking is undeniably the primary
cause, people with a parent, sibling or other first-degree
relative with lung cancer are at increased risk of the disease,
whether they smoke or not.
Screening and diagnosis
Screening for lung cancer is controversial. The American
Cancer Society currently doesn't recommend screening tests
for lung cancer, even in high-risk individuals. But some
doctors believe that smokers, especially those 50 years
or older, should have annual screenings. The debate is becoming
more heated with the increasing use of imaging tests such
as helical and electron beam computerized tomography (CT)
scans that could potentially detect early-stage cancers
more effectively than older tests do — and with far less
exposure to radiation. But CT screening has a serious drawback:
It detects small, benign nodules that commonly occur in
the lungs, leading, in some cases, to needless worry and
unnecessary and invasive tests.
A
standard chest X-ray can reveal an abnormal mass or nodule
in your lungs. And a CT scan may show very small lesions
and whether cancer has spread to other areas. But as with
all types of cancer, lung cancer can be definitively diagnosed
only by looking at a tissue sample (biopsy) under a microscope.
The sample may be removed using one of the following techniques:
* Sputum cytology. If you have a cough and are producing
sputum, looking at the sputum under the microscope can sometimes
reveal the presence of lung cancer cells. Before the test,
you may be asked to breathe a mildly irritating mist to
help you produce more sputum.
* Bronchoscopy. In this test, a flexible tube called a bronchoscope
is passed into your airway. The bronchoscope allows your
doctor to look inside your lungs as well as to take a tissue
sample for examination in the laboratory.
* Mediastinoscopy. In this test, an instrument passed through
a small incision at the base of your neck allows your doctor
to take a biopsy of lymph nodes in your chest. This helps
determine how far the cancer has spread and whether surgery
is a reasonable option for removing the tumor.
* Transthoracic needle biopsy. Using an X-ray or CT scan
for guidance, your doctor takes a small needle and places
it into a mass in your lung, removing a small piece for
study.
* Thoracentesis. If you have fluid in your chest cavity,
your doctor can remove a sample by inserting a thin needle
into your chest between the ribs. The fluid is then examined
in the laboratory for presence of cancer cells. Removing
a large amount of fluid with thoracentesis also can improve
your breathing.
* Video thoracoscopy. In this procedure, your doctor inserts
a tube (endoscope) through a small incision between your
ribs and partially collapses one of your lungs. This creates
a space through which a pen-sized instrument with a video
device is passed between the ribs and through your chest
wall. Your doctor then can perform biopsies of nodules or
masses while watching the procedure on a video screen. Your
lung will expand again after the procedure.
Staging
Staging is a system of classifying information about cancer,
including where and to what extent the cancer has spread.
In many cases, Roman numerals are used to describe stages,
with 0 being the least advanced and IV the most advanced.
Your doctor uses this information to determine what treatment
you need and to evaluate how your cancer might progress.
Non-small
cell lung cancer
Non-small cell lung cancer is staged according to the size
of the tumor, the level of lymph node involvement and the
extent to which the cancer has spread. Stages of non-small
cell lung cancer include:
* Stage 0. At this stage, cancer is limited to the lining
of the air passages and hasn't invaded lung tissue. Stage
0 cancers almost always are found during bronchoscopy, which
is likely to have been performed to assess an abnormality
on a chest X-ray. If found and treated promptly, cancers
at this stage usually can be eliminated.
* Stage I. Cancer at this stage has invaded the underlying
lung tissue but hasn't spread to the lymph nodes.
* Stage II. This stage cancer has spread to neighboring
lymph nodes or invaded the chest wall.
* Stage IIIA. At this stage, cancer has spread from the
lung to lymph nodes in the center of the chest.
* Stage IIIB. The cancer has spread locally to areas such
as the heart, blood vessels, trachea and esophagus — all
within the chest — or to lymph nodes in the area of the
collarbone.
* Stage IV. The cancer has spread to other parts of the
body, such as the liver, bones or brain.
Small
cell lung cancer
Small cell lung cancer is staged differently from non-small
cell types. Rather than using numbers, it's classified as
either limited or extensive:
* Limited. Cancer is confined to one lung and to its neighboring
lymph nodes.
* Extensive. Cancer has spread beyond one lung and nearby
lymph nodes, and may have invaded both lungs, more remote
lymph nodes or other organs.
Staging
tests
Tests to determine how far cancer has spread are of primary
importance in planning treatments. In addition to CT scans,
these tests include:
* Magnetic resonance imaging (MRI). Instead of radiation,
this test uses radio waves and high-powered magnets to produce
internal images of your body. It's especially good at detecting
tumors that have spread to the brain or spinal cord.
* Positron emission tomography (PET) scan. Unlike other
scanning techniques, a PET scan doesn't produce clear structural
images of organs. Instead, it shows images containing areas
of more or less intense color to provide information about
chemical activity within certain organs and tissues. This
chemical activity can indicate whether cancer cells have
spread to nearby lymph nodes, even before the lymph nodes
become enlarged, a distinct improvement over older staging
methods. But PET scans need to be interpreted carefully
because sometimes benign conditions can resemble cancer.
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The information on this page has been extracted from http://www.mayoclinic.com/health/lung-cancer/DS00038/DSECTION=4
