What is Malignant Pleural Mesothelioma?
Malignant mesothelioma is a cancer which affects the thin layer of tissue which lines the body’s major cavities- the chest and the abdomen. In the chest this tissue layer is called the pleura and in the abdomen it is called the peritoneum. Therefore, when mesothelioma affects the lungs it is called pleural mesothelioma but when it affects the abdomen it is called peritoneal mesothelioma. In the UK, pleural mesothelioma tends to be more common than peritoneal mesothelioma.
Mesothelioma and asbestos
The development of mesothelioma is linked with exposure to asbestos. This material was used heavily in UK industries throughout the 1960s, 70s and 80s. It was popular for insulation and fire-proofing, because of its relatively cheap cost, high strength and resistance to heat, electricity and fire. Inhalation (breathing-in) of asbestos fibres in these environments has been shown to be associated with the development of pleural mesothelioma several decades later. Although asbestos has now been banned in the UK, the number of people being diagnosed with MPM continues to rise because of the long delay between exposure to the fibres and development of symptoms. The people who tend to be affected are those who previously worked in industries such as shipbuilding, pipe-laying and insulation.
There are no useful blood tests to look for mesothelioma in people who have been exposed to asbestos and early signs of the disease are often vague and easily mistaken for something less sinister. The disease is also difficult to see clearly on scans and getting a biopsy to prove the diagnosis can be difficult. Many patients therefore get diagnosed late, when their disease is at an advanced stage and when we are unfortunately only able to treat their symptoms rather than the underlying cancer.
The symptoms of pleural mesothelioma are often a consequence of the cancer growing in the lining of the lung. Extra fluid tends to be produced by the unhealthy pleura and is unable to drain away properly, so it collects between the chest wall and the lung. This is called a pleural effusion and can make patients feel very breathless, tired and unwell. This fluid can be drained away to help improve these symptoms, but it may come back and require further similar treatments. Even if patients don’t have a pleural effusion, they may find themselves more breathless with MPM, since the cancer can make the lining of the lung stiffer. This can make it less easy to expand the lung and as a result patients may find taking a deep breath more difficult.
Breathlessness and pain are the most common symptoms which patients get with MPM, but when patients have had their illness for a while, pain tends to become the bigger problem. There are many reasons why pain can occur.
• The pleura has a nerve supply and if it becomes irritated and inflamed with the growth of the cancer then this can cause the nerves to trigger pain signals to the brain. Often this nerve pain can be ‘sharp’ and ‘burning’ and can come on without warning, making it very difficult to control.
• Mesothelioma can grow around and into the surrounding ribs. This can trigger bone pain which patients often describe as a constant dull ‘gnawing’ pain.
• In areas where the cancer has become particularly bulky, it can press on other structures around it and pain can occur as a result of this pressure.
Radiotherapy for pain
This variety in the causes of pain in MPM explains why doctors often have to use a variety of pain killers, which all work in different ways, to try to control symptoms. Very often, however, pain remains uncontrolled and radiotherapy is often used at this stage to try to improve the patient’s symptoms. Since the results of the SYSTEMS study were published, the standard dose of radiotherapy used in this trial has become the ‘gold standard’ radiotherapy dose.