What is cancer?
Firstly it is important to understand that cancer is not a single illness, there are many different types and mesothelioma is just one type.
Our bodies are made of tiny building blocks called cells, cancer is a disease of these cells. Cells from different parts of the body look and work differently and millions of new cells are made everyday to replace those lost through old age or wear and tear.
Throughout the body new cells are produced when existing cells divide into two and there is normally a perfect balance between those that are dying and those that are dividing. This vital balance is controlled by a very complicated process, if control of this process is lost it can lead to too many cells being produced which results in a tumour.
Most tumours are not cancerous (sometimes described as benign) and they remain in the area where they first developed. A wart is a common example.
The development of cancer involves a change in the quality of the cells as well an increase in the quantity. They become more aggressive, destructive and independent of normal cells. They are able to invade surrounding tissues, glands and blood vessels and thus spread away from where they started to divide and grow. When the cancer cells reach a new site they may go on dividing and form a new tumour, this is often referred to as a secondary or metastasis.
What is mesothelioma?
In the UK about 2500 people a year are diagnosed with mesothelioma. It is also known as ‘diffuse’ or ‘malignant’ mesothelioma. Mesothelioma is a form of cancer that affects the mesothelium. The mesothelium is a thin membrane that lines the inner surface of:
- The chest wall, where it is known as the pleura
- The abdomen where it is known as the peritoneum
- The testicles
The mesothelium also surrounds organs within these cavities for example the heart, lungs and intestines. It is far more common to have mesothelioma in the chest than in the abdomen. There is approximately one case of peritoneal mesothelioma to every 12 cases of pleural mesothelioma.
Mesothelioma is more common in men than in women and nearly half of the people diagnosed with the disease are over 75 years old.
The pleural lining has two layers: the visceral (inner) layer is next to the lung and the parietal (outer) layer lines the chest wall. The pleura produces fluid that lubricates the space between the two layers, this allows the two layers to slide comfortably over each other as we breathe in and out.
Pleural mesothelioma causes the pleura to thicken. This thickening of the pleura might begin to press onto the lungs or attach itself to the inside of the chest wall. In either case the expansion of the lung becomes progressively restricted by the tumour. Fluid, sometimes several litres, can collect between the two layers of the pleura; this affects the lungs ability to expand and causes the person to feel breathless. This is known as a pleural effusion.
Symptoms of pleural mesothelioma
- shortness of breath
- chest pain
- loss of appetite
- weight loss
- fatigue and lethargy
The peritoneum also has two layers the inner (visceral) layer which is next to the abdominal organs and the outer (parietal) layer which lines the abdominal wall.
Peritoneal mesothelioma causes the peritoneum to thicken and fluid to collect in the abdomen. This collection of fluid is called ascites and causes the abdomen to swell.
Because pleural mesothelioma is more common and often spreads to the peritoneal cavity, it is sometimes necessary to determine if pleural mesothelioma is the primary cancer.
Symptoms of peritoneal mesothelioma
- abdominal pain
- abdominal swelling or feeling bloated
- constipation or diarrhoea
- loss of appetite
- weight loss
The most common symptoms for pleural and peritoneal mesothelioma are listed here, but there may be others. You can find out more about treatments for these symptoms in the Controlling Symptoms section.
Exposure to asbestos is responsible for up to 9 out of 10 mesothelioma cases. There are thought to be other rare causes of the disease but none are fully understood at this time. The disease has been described in medical literature since 1870 although the first suspicion linking asbestos and mesothelioma did not appear in the UK until 1935 and a definite link was not reported until 1960.
What is asbestos?
Asbestos is a natural fibrous mineral that is widely distributed in nature. Its name derives from the Greek meaning ‘inextinguishable’, which suggests its ability to resist heat and fire have always been understood. It is the ability to resist heat and fire that resulted in asbestos being used widely in industry, shipbuilding and construction particularly during and after World War II.
Currently the largest producers of asbestos are Russia, China and Canada. Russia and China use a majority within their own country however Canada dominates the export market.
There are three main types of asbestos, blue (crocidolite), brown (amosite) and white (Chrysotile).
They are all harmful but blue and brown asbestos are recognised as the most hazardous and have not been imported into the UK since 1985. However, they are still present in buildings and equipment built or produced before the ban. White asbestos was banned in the UK in 1999.
It is asbestos dust or airborne fibres, which cause harm when inhaled or ingested. Asbestos materials left undisturbed probably pose no significant threat. Asbestos fibres are very fine and if they are breathed in they can reach the smallest areas of the lung where they cannot be breathed or coughed out. Once they have lodged in the lung the body’s defence mechanism tries to break them down and remove them which leads to swelling and inflammation in the surrounding area.
The fibres can also penetrate the edge of the lung and settle in the pleural lining. The fibres can also be swallowed and in a similar way can lodge in the abdomen and work their way to the peritoneum that lines the abdomen where the same swelling and inflammation can occur.
If you have been exposed to asbestos at any time you are potentially at risk although it should be made clear that the majority of people who have been exposed to asbestos dust do not suffer ill health as a result. There is no way of identifying who or why some people go on to suffer and others remain unaffected.
Generally, asbestos is only a risk if you disturb or damage it and cause fibres to be released into the air. If asbestos containing materials are in good condition and in a position where they are not going to be disturbed or damaged then it may be safer to leave them where they are and ensure that any risks are properly managed. Professional advice should be sought.
Asbestos was used in many different products and buildings from the 1950s to the mid 1980s. Many homes may, therefore, contain asbestos containing material.
If you are concerned about asbestos in the home, and the potential removal of it, you should contact the local council in your area. They will be able to provide professional advice.
Mesothelioma is not an easy disease to diagnose. Often a number of investigations and hospital visits are required and even then, it is not always possible to be certain that mesothelioma is present.
Symptoms and referral
The earliest signs of the disease can be quite vague. The most common symptoms are breathlessness, chest pain, fatigue and weight loss.
In most cases the first sign of something being wrong is when breathlessness or pain in the chest occur as a result of an effusion. This is when fluid accumulates in the space (pleural cavity) between the two layers of the pleural lining. At this stage the patient will often visit their GP.
Once a diagnosis of mesothelioma has been made, it is helpful for the doctor to determine the stage of the disease. The stage describes the size and position of the cancer and whether or not there is evidence that it has spread to nearby tissues or to other, more distant, sites. Staging can be helpful in assessing prognosis, in making recommendations for treatment and in assessing and comparing the results of treatment. However, staging mesothelioma is difficult, the tumour is rarely present in a measurable manner.
Different systems have been established for staging mesothelioma. Here is a shortened version of the International Mesothelioma Interest Group (IMIG) staging system:
Disease limited to the pleura only on one side of the chest.
Disease limited to the pleura on one side of the chest but the cancer cells have extended from the pleura into the underlying lung tissue or muscle of the diaphragm.
The cancer has either spread beyond the pleura to glands in the chest and/or has advanced deeper into the tissues surrounding the pleura.
The cancer has spread to distant organs or tissues or invaded deeply into tissues close to the pleura e.g. across the diaphragm into the abdomen, into the pleura of the opposite lung or into the spine or heart muscle.
In order to stage the extent of disease a CT scan is usually carried out and may be all that is required. Other scans that are occasionally used in some centres include Magnetic Resonance Imaging (MRI), Ultrasound Scan (USS) and Positron Emission Tomography (PET) scans.
Multi-disciplinary teams (MDTs)
To assist in the diagnosis and treatment of cancer, hospitals have teams of doctors and nurses, each with their own areas of expertise, who work together to try and provide the best care for patients.
These are known as Multi-Disciplinary Teams (MDTs). These teams are made up of Consultant doctors, radiologists, pathologists, oncologists (doctors who treat cancers using chemotherapy and radiotherapy), surgeons and specialist nurses. These teams meet regularly to discuss the cases of individual patients, with confirmed or suspected mesothelioma, to agree on the likelihood of the diagnosis being correct, on the stage of the disease and best treatment strategy. The wishes of the patient are taken into close consideration when treatment plans are discussed. Following MDT discussion, treatment options will be explained to the patient and referrals will be made as necessary.
Some centres in the UK now have regional mesothelioma MDTs where complex cases can be discussed, although for most patients, discussion will be held in a lung cancer (pleural mesothelioma) or gastro-intestinal (peritoneal mesothelioma) MDT.