Lung cancer


Lung cancer is the uncontrolled growth of cancerous tumours in the lungs.

Exposure to carcinogens, such as those present in tobacco smoke, immediately
causes small changes to the tissue lining the bronchi of the lungs (the
bronchial mucous membrane). This effect is cumulative, and over time with
continued exposure more and more tissue gets damaged until a tumour
develops. If the tumour grows inwards it may obstruct the air passageway,
causing breathing difficulties. The lungs may then collapse and infections
can develop, leading to lung abscess. The patient here would start to cough
up blood-stained material. However, if the tumour grows outwards in to the
lung it may not even be noticed by the patient before it starts to spread to
other parts of the body. Common symptons include: coughing up blood or
lung-material bad, chronic, cough, wheezing, chest pains, weight loss or
loss of appetite, shortness of breath.

Types

There are two main types of lung cancer categorised by the size of the
cancerous cells seen under a microscope: small and non-small cell lung
cancer.

Small cell types:
Small cell carcinoma (also called oat cell carcinoma) is the less common
form of lung cancer, making up 20% of cases. It tends to start in the larger
breathing tubes and grows rapidly becoming quite large.

Non-small cell types:
Epidermoid carcinoma (or Squamous cell carcinoma) also starts in the larger
breathing tubes but grows slower meaning that the size of these tumours
varies when on diagnosis.
Adenocarcinoma (or for slower growing forms alveolar cell cancer) is a form
which starts near the surface of the lung.
Large cell carcinoma is a fast-growing form that grows near the surface of
the lung.

The listed types add up to 90% of all cases of lung cancer. Other forms
include carcinoid, cylindroma, mucoepidermoid and malignant mesothelioma.

Causes

There are four major reasons why people get lung cancer (and actually cancer
in general):

   * Carcinogens such as those contained in cigarretes
   * Radiation
   * Genetic susceptibility
   * viruses

Smoking, particularly of cigarettes, is believed to be by far the main cause
of cancer, which in at least in theory makes it one of the easiest diseases
to prevent. An estimated 80% of lung cancers result from smoking, due to the
hundreds of known carcinogens, such as benzene, present in cigarette smoke.
The length of time that a person continues to smoke as well as the amount
smoked increases there chances of contracting lung cancer. However if
someone stops smoking then these chances steadily decrease as the damage to
their lungs is repaired.

Passive smoking, whereby exhaled smoke is taken up by other people, has
recently been identified as a much larger cause of lung cancer in
non-smokers than previously believed. The US Environmental Protection Agency
(EPA) in 1993 concluded that about 3,000 lung-cancer related deaths were
caused by passive smoking every year, however the true extent is still being
contested among scientists.

Asbestos is another popularly known carcinogen mainly for mesothelioma
(affecting the mesothelium lining lungs, abdomen or heart.) Often this
exposure happens to people unavoidably through their work.

Radon is a colourless and odorless gas derived from the breakdown of
radioactive radium, which in turn is the decayed product of uranium, found
in the earth's crust. It is the second major cause of lung cancer after
smoking. This radiation ionises genetic material, causing mutations that
sometimes become cancerous. Radon gas levels vary over where you live. In
areas such as Cornwall in the UK, radon-gas is a major problem, and fans
have to be installed to drive out the gas. In the US the EPA estimated that
1 in 15 homes have radon levels above the recommended standard.

Oncogenes are genes which is believed make people more susceptible to
cancer. Proto-oncogenes are believed to turn in to oncogenes when exposed to
particular carcinogens. Viruses are suspected to cause cancer in humans, as
this link has already been proven in animals.

Treatment

Treatments for lung cancer depends on the specific form, how far it has
developed and on other details of the patient (eg. age). Common treatments
include surgery, chemotherapy and radiation therapy.

Radiofrequency Ablation is increasing in popularity for this condition as it
is non toxic and causes very little pain. It seems especially effective when
combined with chemotherapy as it catches the cells inside a tumor - the ones
difficult to get with chemo due to a reduced bood supply to the inside of
the tumor. It is done by inserting a small heat proble inside the tumor to
cook the tumor cells. These are then disposed of by the body through normal
eliminative processes.

Susceptibility

The group most likely to develop lung cancer are the over-fifties who also
have a history of smoking. Lung cancer is the second most commonly occurring
form of cancer in most western countries, however it is the leading
cancer-related cause of death for men and women. It is expected that in 2001
there will be 169,500 new cases of lung cancer; 90,700 in men and 78,000 in
women. Although the rate of men dying from lung cancer is declining in
western countries, it is actually increasing for women due to the increased
take up of smoking in this group.

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