Mesothelioma

What is mesothelioma?

The mesothelium is a thin layer of cells that covers the lungs, lines the chest wall, wraps the abdominal organs and surrounds the heart. It produces a small amount of fluid so that organs can glide smoothly. Mesothelioma begins when these cells become cancerous, usually after asbestos fibers lodge in the lining and cause decades of inflammation and DNA damage.

The cancer spreads along the lining, thickening it like a rind and encasing the lung or bowel. It often produces fluid that collects around the lung or in the abdomen.

Types by location

Types by cell appearance

• Epithelioid: the most common and best-outlook type.
• Sarcomatoid: less common and more aggressive.
• Biphasic: a mixture of both.

Mesothelioma symptoms

Symptoms build slowly and are often mistaken for more common conditions.

Pleural mesothelioma

• shortness of breath, from fluid around the lung (pleural effusion) or a stiffened lining
• a dull, aching pain in the chest wall or shoulder, often on one side
• a dry, persistent cough
• fatigue, fever and heavy sweating, especially at night
• unexplained weight loss and loss of appetite
• in later stages, hoarseness, swallowing difficulty and lumps under the skin of the chest

Peritoneal mesothelioma

• swelling of the abdomen from fluid (ascites)
• abdominal pain or discomfort
• nausea, constipation or diarrhea
• weight loss despite a growing waistline

Causes and risk factors

Asbestos exposure

Asbestos causes about 8 in 10 cases. Asbestos is a group of natural mineral fibers used widely in insulation, roofing, brake pads, cement, ship and boiler work until it was restricted in many countries from the 1970s to 2000s. When disturbed, the fibers are breathed in or swallowed and are almost impossible for the body to clear.

Higher-risk groups include:

• shipyard, construction, demolition, insulation, plumbing, electrical and boiler workers
• mechanics who worked on brakes and clutches
• military veterans, especially Navy
• family members exposed to dust brought home on work clothes
• people renovating older buildings without protection

There is no safe level of asbestos exposure, but risk rises with the amount and length of exposure. Smoking does not cause mesothelioma by itself, but it greatly increases the risk of asbestos-related lung cancer. Heavy exposure can also scar the lung tissue itself, a separate disease called asbestosis.

Other risk factors

• previous radiation therapy to the chest
• erionite, a mineral fiber found in some regions such as parts of Turkey
• inherited mutations in the BAP1 gene, which raise the risk of mesothelioma and some eye and skin cancers

How mesothelioma is diagnosed

1. History of exposure: your doctor will ask about every job you have had, military service and home renovations.
2. Chest X-ray and CT scan: show pleural thickening, fluid and sometimes calcified plaques, a marker of past asbestos exposure.
3. Fluid sample (thoracentesis or paracentesis): fluid is drained with a needle and examined for cancer cells, though this often cannot confirm the diagnosis alone.
4. Biopsy: the key test. Usually a thoracoscopy (a camera passed through a small cut in the chest) to take tissue samples and often drain fluid at the same time. Needle biopsies guided by CT are used in some cases.
5. PET-CT and sometimes MRI: stage the cancer and help decide whether surgery is possible.

Mesothelioma must be distinguished from lung cancer and from cancers that have spread to the pleura, which needs special lab stains.

Mesothelioma treatment

Treatment is planned by a specialist team and depends on the type, stage and fitness.

• Immunotherapy: the combination of nivolumab and ipilimumab improves survival compared with chemotherapy in many patients with pleural mesothelioma, particularly the non-epithelioid types. Pembrolizumab with chemotherapy is another option.
• Chemotherapy: pemetrexed with cisplatin or carboplatin, sometimes with bevacizumab.
• Surgery: in carefully selected patients with early epithelioid disease, a pleurectomy and decortication (removing the lining) may be offered with other treatments. The more radical extrapleural pneumonectomy is now rarely performed.
• Radiation therapy: to relieve pain, or after surgery.
• Peritoneal mesothelioma: cytoreductive surgery with heated chemotherapy washed through the abdomen (HIPEC) can give long-term survival in selected patients.
• Clinical trials: many patients are offered trials of new therapies.

Relieving symptoms

• Draining fluid around the lung eases breathlessness. If it keeps returning, talc pleurodesis seals the space, or an indwelling pleural catheter lets fluid be drained at home.
• Pain control with medicines, nerve blocks or radiation.
• Palliative care from diagnosis improves comfort and quality of life alongside cancer treatment.

Outlook and life expectancy

Mesothelioma is usually diagnosed at an advanced stage. Median survival for pleural mesothelioma is about 1 to 2 years with modern treatment, and around 10% of people live 5 years or more. Outcomes are better with the epithelioid type, early stage, good fitness and peritoneal mesothelioma treated with surgery and HIPEC, where many people live 5 years or longer.

Compensation and benefits

Because mesothelioma is almost always caused by occupational asbestos, people diagnosed may be eligible for compensation through asbestos trust funds, workers' compensation, legal claims or veterans' benefits. A social worker at a mesothelioma center can explain options.

Prevention

• Do not disturb materials that may contain asbestos in buildings constructed before about 1980. Have them tested and removed by licensed professionals.
• Follow workplace protection rules, including respirators and decontamination.
• Do not smoke, to reduce the related risk of lung cancer.

Frequently asked questions

What are the first signs of mesothelioma?

The first signs are usually shortness of breath and a dull pain in the chest or shoulder, often with a dry cough, tiredness and night sweats. Peritoneal mesothelioma starts with a swollen or uncomfortable belly. These symptoms are common to many conditions, so mention any asbestos exposure to your doctor.

How long after asbestos exposure does mesothelioma develop?

Typically 20 to 50 years. That is why most people are diagnosed after age 65, even though their exposure ended decades earlier. Short or low-level exposure carries a lower risk, but no level of exposure is considered completely safe.

Is mesothelioma the same as lung cancer?

No. Lung cancer starts in the airways and lung tissue. Mesothelioma starts in the lining around the lungs. Both can be caused by asbestos, and asbestos plus smoking greatly raises lung cancer risk, but they are diagnosed and treated differently.

Can mesothelioma be cured?

A cure is rare, but treatment can control the disease and ease symptoms. Some people with early, epithelioid pleural mesothelioma or peritoneal mesothelioma treated with surgery and heated chemotherapy live many years. Immunotherapy has improved survival for many patients.

What is the life expectancy with mesothelioma?

With modern treatment, median survival for pleural mesothelioma is about 1 to 2 years, and roughly 1 in 10 people live 5 years or more. Peritoneal mesothelioma treated with surgery and HIPEC has a better outlook. Individual outcomes vary with type, stage and health.