Lung cancer – a brief guide to the facts
Lung cancer is the second most common form of cancer in the UK after breast cancer. Smoking and passive smoking cause nine out of ten lung cancers.
Men are more likely to be affected, although the number of women with lung cancer has been increasing. There are over 38,300 new cases of lung cancer in the UK each year.
Factors implicated in developing lung cancer
The most important risk factors for lung cancer are listed below:
Tobacco smoking
Smoking is by far the commonest risk factor for developing lung cancer. Tobacco smoking (e.g. cigarettes, pipes, cigars) accounts for 9 out of 10 cases of lung cancer.
Here are some facts about smoking and lung cancer
- The more you smoke, the more likely you are to get lung cancer. It seems that the length of time you have been a smoker is the most important factor.
- Filtered and low tar cigarettes might not increase your risk quite so much, but most smokers cancel this out by taking more, deeper puffs or smoking more cigarettes
- As soon as you stop smoking, your risk of lung cancer starts to go down
- Passive smoking (breathing other people's cigarette smoke) increases the risk of lung cancer, but it is still much less than if you smoke yourself
It is almost impossible to work out the risk of occasional smoke exposure to second hand smoke for non smokers (passive smoking). We know that the risk of lung cancer for passive smokers goes up the more cigarette smoke they are exposed to. Overall, people exposed to environmental tobacco smoke at work or at home have their risk of lung cancer increased by about a quarter compared to people who are not exposed to environmental tobacco smoke. Heavy exposure to environmental tobacco smoke at work has been shown to double the risk of lung cancer.
Although Cigarette smoking is more risky pipe and cigar smokers are still much more likely to get lung cancer than non smokers. (They are also much more likely to get cancer of the mouth or lip.)
In the past lung cancer has always been more common in men than women. Now, as more women smoke, it is almost as common in women.
Age
The risk of lung cancer increases with age. Three-quarters of lung cancer deaths occur in people over 65.
Radon gas
High indoor levels of radon, a naturally occurring radioactive gas, are responsible for a small but significant percentage of lung cancers.
Exposure to environmental chemicals
Exposure to carcinogens such as asbestos, nickel, chromium, polycyclic aromatic hydrocarbons, silica and diesel fumes can increase the risk of lung cancer, particularly when combined with smoking.
Social background
Lung cancer rates are strongly linked to socioeconomic deprivation. Rates in the most deprived groups are two to three times higher than the least deprived. This reflects, in large measure, the smoking habits of these groups.
Protective factors
Diet
A diet that is rich in fruit may slightly reduce the risk of the disease, but this protective effect is small compared to the harm caused by smoking.
Types of lung cancer
Primary lung cancer
This is cancer that develops from cells within the lungs, the bronchi (air passages) trachea (wind pipe) or lining of the lungs.
There are several different types of primary lung cancer. These are divided into two main types:
- Small cell lung cancer (SCLC)
- Non-small cell lung cancer (NSCLC)
Small cell lung cancer
About 20 out of every 100 lung cancers diagnosed are this type. Small cell lung cancer is so called because the cancer cells are small cells that are mostly filled with the nucleus (the control centre of cells). You may hear it called 'oat cell' cancer. This type of cancer is usually always caused by smoking. It is very rare for someone who has never smoked to develop it. Small cell lung cancer often spreads quite early on and so doctors often suggest treatment with chemotherapy rather than surgery.
Non-small cell lung cancer
There are three types of non-small cell lung cancer. These are grouped together because they behave in a similar way and respond to treatment differently to small cell lung cancer. The three types are:
- Squamous cell carcinoma
- Adenocarcinoma
- Large cell carcinoma
Occasionally it is not possible to work out which type of non small cell lung cancer you have. If the cells in the biopsy are very undeveloped, it just may not be possible to tell. Undeveloped cancer cells are known as undifferentiated cells. So you will be told you have undifferentiated non-small cell lung cancer. This will not make any difference to your treatment as all non-small cell lung cancers are treated the same way at present.
Squamous cell cancer
Squamous cell cancer is the most common type of lung cancer. It develops from the cells that line the airways and you often find it near the centre of the lung in one of the main airways (the left or right bronchus). This type of cancer is often due to smoking. The incidence of squamous cell cancer is going down in the UK.
Adenocarcinoma
Adenocarcinoma also develops from the cells that line the airways. But it develops from a particular type of cell that produces mucus (phlegm). You often find it in the outer regions of the lungs. The incidence of adenocarcinoma is increasing and it may soon become more common in the UK than squamous cell lung cancer.
They are different because they originate in different types of cells in the lungs. Around 80% of lung cancer is NSCLC.
Large cell carcinoma
Large cell lung cancer is called this because the cells look large and rounded when they are looked at under a microscope. This type of lung cancer tends to grow quite quickly.
Mesothelioma
A rare type of cancer which affects the covering of the lung (the pleura). It is often caused by exposure to asbestos.
Secondary lung cancer
Secondary lung cancer is cancer that has spread from somewhere else in the body to the lungs. There are quite a few different cancers that can spread to the lungs, including breast cancer and bowel cancer.
The choice of cancer treatment depends on where the cancer started. For example when cancer spreads to the lung from the breast, the cells are breast cancer cells, not lung cancer cells. So they respond to breast cancer treatments. In a similar way, cancer that has spread from the bowel should respond to bowel cancer treatments.
Signs and symptoms
People who notice any of these symptoms should see their doctor. However symptoms may have other causes, such as chronic smoking-related lung disease.
General symptoms of lung cancer
Although not exclusive to lung cancer, the following symptoms should be taken seriously and might arouse suspicion:
- Having a cough most of the time
- A change in a cough you have had for a long time
- Being short of breath
- Coughing up phlegm (sputum) with signs of blood in it
- An ache or pain when breathing or coughing
- Loss of appetite
- Fatigue
- Losing weight
Less common symptoms of lung cancer
There are other symptoms of lung cancer that are less common. They can be associated with more advanced lung cancer. You may have:
- A hoarse voice
- Difficulty swallowing
- Changes in the shape of your fingers and nails called clubbing.
- Swelling of the face caused by a blockage of a main blood vessel from the head (SVCO)
- Swelling in the neck caused by enlarged lymph nodes
- Pain or discomfort under your ribs on your right side (from the liver)
- Shortness of breath caused by fluid around the lungs (called pleural effusion)
Pancoast tumours
Doctors sometimes call lung cancer that is growing right at the top of the lung a 'Pancoast tumour'. These tumours can cause very specific symptoms. The most common is severe shoulder pain. They can also cause a collection of symptoms called 'Horner's syndrome'. These are:
- Drooping or weakness of one eyelid
- Small pupil in that eye
- Loss of sweating on that same side of the face
These symptoms of Horner's syndrome are caused by the tumour pressing on or damaging a nerve that runs up from the neck to that side of the face.
Odd symptoms of lung cancer
Sometimes lung cancer cells produce hormones that get into the bloodstream. These hormones can produce strange symptoms that you may not realise are anything to do with lung cancer. You may hear your doctor call these 'paraneoplastic symptoms' or say you have 'paraneoplastic syndrome'. These hormone related symptoms include:
- Pins and needles or numbness in fingers or toes
- Muscle weakness
- Drowsiness, weakness, dizziness or confusion
- Breast swelling in men
- Tendency to have blood clots (thrombosis)
These symptoms are rarely caused by lung cancer. But they can be. So it is important you tell your doctor about any new symptoms you have noticed. They may be nothing to do with your cancer and so your mind can be put at rest. If they are, then they can treat them and help you to feel better.
Detection
Your doctor will carry out an examination and ask questions about any previous medical problems. If you are referred a specialist may carry out further tests, such as:
- Chest X-rays
- Bronchoscopy
- Mediastinoscopy
- Lung biopsy
- CT, MRI, or other scans.
Treatment
Possible treatments for lung cancer may include:
Surgery
If at all possible, non-small cell lung cancer will be treated by surgery to remove all or part of the cancer. However, surgery is rarely a suitable treatment option for small cell lung cancer.
Radiotherapy
Cancer specialists use radiotherapy to treat all types of lung cancer. It can be given on its own or with another treatment such as chemotherapy or surgery.
Chemotherapy
Chemotherapy is standard treatment for most patients with small cell lung cancer, as this type of cancer usually reponds well to this treatment. Many drugs are active against small cell lung cancer, and these can be used in various combinations. Chemotherapy is also increasingly being offered for non-small cell lung cancer.
If the cancer is advanced, doctors will offer treatment to control and manage some of the effects and symptoms, such as pain, breathing problems and weight loss.
Screening for lung cancer?
What is screening?
Screening means testing people for the early stages of a disease before they have any symptoms. It is an important part of health care for some cancers. But before screening for any type of cancer can be carried out, doctors must have a test that will reliably detect early disease.
Spiral CT scanning
Lung cancer is often picked up on chest X-ray. But by the time it is diagnosed this way, it is often quite advanced. Researchers in the USA are trying to find out whether screening with a type of scan called spiral CT scanning would help them diagnose lung cancer earlier and improve the cure rate. This is a large trial, involving 50,000 people. It opened in 2002 and isn't due to finish until 2009.
Bronchoscopy
Researchers are also investigating a different way of carrying out a test called a Bronchoscopy in people at high risk of lung cancer. This is called fluorescence bronchoscopy and involves using blue and white light to examine the lining of the airways. This trial finished recruiting patients in November 2005, and it will be some time before we know the results. It is still early days and at the moment there is no clearly effective test for lung cancer in people who do not have any symptoms.
Screening for people at a high risk of lung cancer
Doctors must also be aware of the potential harm of any screening test. The lungs are very sensitive to radiation. Therefore frequent X-rays may not be a sensible solution. For screening to be introduced, we need a test that is simple, quick, not too expensive and not harmful. It is always more cost effective to screen people at high risk, rather than screen everyone. For lung cancer, we know who is at higher risk - anyone who smokes. As soon as you stop smoking, you start to lower your risk.
Prevention
Of course smoking is the biggest avoidable risk factor for lung cancer, as it causes nine in ten cases of the disease. One of the best ways to avoid lung cancer is to quit smoking and avoid exposure to passive smoking.
Article copyright YourDoc Medical Ltd 2010. All rights reserved.
