Peritoneal mesothelioma: symptoms, causes, diagnosis and treatment

The NHS describes mesothelioma as a rare type of cancer that can develop in the lining of the body's organs, usually caused by exposure to asbestos. Cancer Research UK explains that it starts in the cells that cover the outer surface of most internal organs, called mesothelial cells, which form a lining called the mesothelium. In most people it starts in the pleura, the tissue covering each lung, and more rarely in the peritoneum, the layer of tissue covering the organs in the tummy.

The peritoneum helps to protect the contents of the abdomen and keep them in place, and it makes a lubricating fluid that helps organs move smoothly against each other. When cancer arises here it is called peritoneal mesothelioma. Cancer Research UK says it does not usually spread to other parts of the body, which means its effects are largely due to what it does inside the abdomen.

Around 2,600 people in the UK are diagnosed with mesothelioma each year, according to Cancer Research UK, and almost 65% are aged 75 and over. Because peritoneal disease is only about 4% of the total, only a small number of people are diagnosed with it each year.

Cancer Research UK says early stage mesothelioma does not usually cause many symptoms, and that symptoms appear as it grows and becomes more advanced. For peritoneal mesothelioma it lists the symptoms below. They are not specific, and most people with them will have a different cause, but they should be checked.

• Pain in the tummy (abdomen).

• Swelling of the abdomen.

• Feeling or being sick.

• Poor appetite.

• Losing weight when not dieting.

• Diarrhoea or constipation.

Cancer Research UK says you should see your GP if you have these symptoms, particularly if you have been exposed to asbestos in the past. It says your symptoms are unlikely to be cancer but it is important to get them checked, because the earlier a cancer is picked up the easier it is to treat. It advises seeing your GP about any change that is not normal for you.

Persistent swelling of the tummy, ongoing pain or unexplained weight loss are reasons to be assessed. If you have severe sudden abdominal pain or feel very unwell, use NHS 111 or call 999 as you would for any acute abdominal problem.

Cancer Research UK says asbestos is the biggest cause of mesothelioma in the UK and that exposure to large amounts for a long period increases the risk. Many people with peritoneal mesothelioma have also been exposed to asbestos. It explains that asbestos fibres can be breathed in, work their way into the pleura and cause gene changes, and that some fibres can be coughed up and swallowed, which is probably the cause of peritoneal mesothelioma.

The link between asbestos and mesothelioma was found in the 1960s, because of the heavy use of asbestos in industry from the end of the Second World War until the mid-1970s. Mesothelioma is most common in those exposed at work, for example in manufacturing using asbestos or using asbestos products in construction or engineering, including metal plate workers, carpenters, plumbers and mechanics, and possibly painters, because until the 1990s some paints contained asbestos. It may not develop until 15 to 60 years after exposure. Families of people exposed to asbestos may have a higher risk because fibres can be carried home on clothes.

Some people with mesothelioma say they have no history of exposure to asbestos. Cancer Research UK says you may be able to claim compensation if you get mesothelioma because of asbestos exposure and suggests talking to a solicitor as early as possible.

Cancer Research UK says you usually start by seeing your GP, who asks about your general health and symptoms, may examine you and arrange tests, and may refer you to a specialist. It says you usually have a number of tests to check whether you have mesothelioma, how big the cancer is and whether it has spread. For symptoms that could be due to mesothelioma, the GP should arrange an urgent chest X-ray or a specialist referral.

In practice, investigation of a swollen or painful abdomen commonly involves scans such as CT and a sample of tissue or fluid from the abdomen, but the sources used for this guide do not describe the individual tests in detail, so your specialist team will explain which are needed in your case. Treatment decisions are made by a specialist multidisciplinary team once the type and stage are known.

Cancer Research UK says mesothelioma can be difficult to treat and is often diagnosed at an advanced stage, so most treatments aim to control the cancer for as long as possible and keep symptoms under control. For peritoneal mesothelioma the options include chemotherapy, and a few people might have surgery. Radiotherapy is not usually given for peritoneal mesothelioma.

Cancer Research UK says survival depends on many factors, including the stage and type of the mesothelioma, that no one can tell you exactly how long you will live and that statistics can only be a general guide. Because mesothelioma is less common, survival is harder to estimate and some of the statistics are based on a small number of people. The figures it gives are for all mesotheliomas in England, not peritoneal disease alone: 45 out of 100 people survive for 1 year or more after diagnosis and more than 5 out of 100 survive 5 years or more.

Other factors it lists include the cell type, with the epithelial type tending to do better, how well you are overall (performance status), and normal blood counts. Your specialist team can give you information about your own outlook.

Cancer Research UK says practical and emotional support is available to help you cope with a diagnosis of mesothelioma during and after treatment, and that clinical trials can help to improve the outlook for people with the condition. A specialist nurse is usually the main point of contact in the hospital. Mesothelioma charities and cancer information services can help with questions about benefits, compensation and living with the disease.

It is natural to feel overwhelmed. Telling the team about worries, including low mood or anxiety, is part of care, and the team can arrange emotional support alongside medical treatment.

On the NHS, a suspected peritoneal mesothelioma is investigated through an urgent cancer pathway and treated by a specialist team, free at the point of use. Because the condition is rare, care is concentrated in centres with experience. Some people also seek a private opinion or a second opinion; it is reasonable to ask the NHS team to review the scans and pathology with you, and to ask any provider how often they treat this rare cancer.