The lungs
Your lungs sit
inside your ribcage. There are two of them and they are shaped like
cones.
When we breathe in,
air is drawn through the nose or mouth, into the throat, and down
the windpipe (trachea)
into the chest. The windpipe branches into two tubes called bronchi, one going to each lung. Inside the lungs, the bronchi
branch out many times, like a tree, to form smaller bronchi and then
thousands of tiny tubes. These tiny tubes are called bronchioles and end up at tiny, bubble-like air sacs. These air
sacs make the lungs spongy.
The lungs are
covered by two layers of thin lining called the pleura. This is about as thick as plastic cling wrap. The inner
layer is attached to the lungs and the outer layer lines the chest
wall and diaphragm. Between the two layers is the pleural cavity. This cavity (like a cave) is almost empty—the
two layers of pleura slide against each other. They are moist and
smooth so that your lungs can move smoothly against the chest wall
as you breathe.
Lung cancer
Lung cancer is
cancer of some of the cells in part of your lung.
There are different
types of lung cancer. Lung cancers are named by the type of cell
affected. There are two main types: small cell
carcinomas and non-small cell carcinomas.
Small cell
carcinomas
Around 15% of lung
cancers are small cell carcinomas. They are also called ‘oat cell’
carcinomas because of the shape of the cells. This cancer is hard
to detect and can spread to other parts of the body before it is
found.
Non-small cell
carcinomas
Non-small cell
carcinomas affect the cells that line the main bronchi. There are different types including: squamous cell carcinoma, adenocarcinoma, large cell carcinoma, and bronchiolo-alveolar cell carcinoma.
As these cancers
grow they can spread into the chest wall and local lymph nodes. Squamous cell carcinoma has a lower rate of
spread than other types of lung cancer and is generally discovered
earlier, resulting in the best prognosis following treatment.
Causes of lung
cancer
As with many
cancers, we do not know the cause in all cases. Cigarette smoking is
the major cause of lung cancer but it is not known why one smoker
develops lung cancer and another does not. Up to 90% of lung cancers
are caused by smoking. Lung cancer occurs most often in adults
between the ages of forty and seventy who have smoked cigarettes for
at least twenty years. Many started smoking as teenagers.
There is also
increasing evidence to suggest that passive smoking cancer bring
about disease in adults, children and infants.
Some occupational
exposures may be linked with lung cancer, including contact with the
processing of steel, nickel, chrome and coal gas. Exposure to
radiation causes an increased risk of all cancers, including lung
cancer. Miners of uranium, fluorspar and haematite may be exposed to radiation by breathing air contaminated with radon gas.
How common is lung
cancer?
About 20,000
Victorians develop cancer every year—about 2,000 are lung cancer.
Diagnosing lung
cancer
Symptoms
Some people have no
symptoms, but learn that they have lung cancer when they have a
routine chest x-ray. Others find out something is wrong when
breathing becomes harder or they have trouble getting over
bronchitis.
The most common
symptom of lung cancer is a cough that won't go away or a change in
a cough that has been present for some time. In the earlier stages
of lung cancer, you may also have one or more of the following
symptoms:
In the later stages
of lung cancer, people may experience:
If the cancer has
spread to other parts of the body, there may be other symptoms that
seem unrelated to the lungs.
Doctors and other
health professionals who treat lung cancer
If your doctor
thinks you might have lung cancer, you will be sent for further
tests. If a diagnosis of cancer is made, you will then be sent to a
specialist who will advise you about treatment options. There are
many different health specialists involved with treating lung cancer
including:
-
respiratory
physicians, who are usually responsible for investigating the
symptoms, making a diagnosis and staging the disease
-
thoracic (chest)
surgeons, who are responsible for some biopsies and removing
cancers if they can be operated upon
-
medical
oncologists, who are responsible for chemotherapy
-
radiation
oncologists, who are responsible for radiotherapy
-
dietitians, who
will recommend the best diets to follow
-
nurses, who will
help you through all stages of your cancer experience
-
psychologists, who
help people with emotional and social concerns
-
speech
pathologists, who help people with speech and swallowing problems
-
social workers,
physiotherapists and occupational therapists, who will advise you
on support services and help you to get back to normal activities.
How lung cancer is
diagnosed
If lung cancer is
suspected, your doctor will first ask you about your past and
current health, smoking and work history, and then examine you
physically. You may then need to have some tests. Some of these
tests can show if cancer has spread from the lungs to other parts of
the body.
Chest x-ray
An x-ray of the chest can find cancers as small as one
centimetre. Sometimes, a lung cancer is found on a chest x-ray
that has been taken for other reasons.
Sputum cytology
This test is an
examination of sputum (phlegm) under a microscope to check for
abnormal cells. Sputum is the thick fluid that you cough up from your
lungs. Early-morning samples are collected for several days—you
will be asked to cough deeply to bring up sputum from your lungs.
You can do this at home and store the sample in the fridge before
taking it to the doctor or pathology collection centre.
Bronchoscopy
A flexible
'telescope' the width of a pencil is inserted into the nose or
mouth, down the trachea and into the bronchus. It allows the doctor to look at the lungs and take a
sample of tissue, if necessary. It can be done after you have had a
light sedative and been given a local anaesthetic spray to the back of the throat. It can be
uncomfortable but is not painful, and can be done as a day
procedure.
Fine-needle
aspiration
This is done if
you have a suspicious-looking lump that cannot be sampled using bronchoscopy but can be reached by putting a needle into the
lump. It is usually done in hospital. You will have a local anaesthetic before the doctor inserts the needle through the
chest wall and into the lump, guided by x-ray pictures, and removes some tissue.
A procedure called
thoracentesis also uses a fine needle. Instead of going into the
lump, fluid from around the pleural cavity is sampled to check for cancer cells.
Mediastinoscopy
This test allows
the doctor to look at lymph nodes in the centre of the chest, to see if they are
affected by cancer. This test is similar to a bronchoscopy, but the tube is inserted through a cut in the
neck and fed down to the lymph nodes around the windpipe. Samples
of the lung may also be removed if necessary. This test is done
using a general anaesthetic. It is usually a day procedure, but sometimes
includes an overnight stay in hospital.
Video-assisted
thoracoscopic surgery
Thoracoscopes are
instruments that are inserted into the chest cavity through small
cuts in the skin. The doctors can see inside your chest using
these instruments, and take tissue samples if necessary.
Often the doctor
uses a very small video camera and is able to guide the
instruments by watching the video screen. You may have up to three
small cuts made in your chest, one for the camera and two for the
surgical instruments. You will have a general anaesthetic and be in hospital for two or three days.
Computerised
tomography (CT) scan
A CT scan is a
special type of x-ray that gives a three-dimensional (3-D) picture
of organs and other structures (including any tumours) in your body. It can be used to find cancers smaller
than those found by x-rays. It can also show whether the lymph nodes around the lungs are swollen.
CT scans are
usually done at a hospital or a radiology clinic. It usually takes
about thirty to forty minutes to do this test, which does not
hurt. You will be asked not to eat or drink before the scan.
You may have a
liquid dye in a drink and/or an injection. This dye makes your
organs appear white on the scans that are taken, so anything
unusual will show more clearly. You will be asked to lie on a
table. The CT scanner, which is large and round like a doughnut,
will then move around you. Most people are able to go home as soon
as their scan is over.
Other scans
Other types of
scans may be used.
A bone scan can show whether cancer has spread to the bones. A small amount of
radioactive substance is injected into a vein. It travels through the bloodstream and collects in areas
of abnormal bone growth. A scanner measures the radioactivity
levels in these areas and records them on x-ray film.
Ventilation/perfusion lung scans work out how the lung will be
affected if part of your lung is removed in an operation.
Positron emission
tomography, also known as a PET scan, involves the injection of a radioactive glucose
solution into the body. Because cancer cells use more glucose than
the rest of the body’s cells, the PET scanner will detect
increased quantities of the radioactive gluose in those areas of
the body where the cancer is. It scans the whole body, including
the bones, but not the brain.
Other tests
You may also have
blood tests and breathing tests. If surgery is an option, it is
very important to measure your breathing capacity. People who
smoke develop emphysema and may have a reduced breathing capacity.
‘Staging’ the
disease
The tests described
above show whether you have cancer. They will also show where the primary cancer is and whether the cancer cells have spread to other parts of your body. This helps your
doctors 'stage' the disease so they can work out the best treatment
for you.
Non-small cell lung carcinoma has the following stages:
-
Stage 0: also
called carcinoma in situ. The cancer cells are confined to the
surface lining of the airway and have not spread into the
underlying tissue.
-
Stage I (1): this
may be a relatively small, self-contained cancer or a larger
cancer that has spread within one lung.
-
Stage II (2):
includes cancers that have spread to the chest wall or lymph nodes within the lung itself.
-
Stage IIIa (3a):
the cancer has spread to the lymph nodes on the same side of the mediastinum.
-
Stage IIIb (3b):
the cancer is close to or involving the trachea or major blood vessels, or has spread to lymph nodes
in the neck or to the other side of the mediastinum.
-
Stage IV (4): the
cancer cells have spread to distant parts of the body and formed
secondary cancers.
Small cell carcinoma is staged in the following way:
-
Limited stage:
cancer is found in one lung and nearby lymph nodes.
-
Extensive stage:
cancer has spread beyong the lung of origin to the opposite lung
or to distant organs.
-
Recurrent: cancer
returns after it has been treated.
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