Malignant mesothelioma is a tumour of mesothelial cells which usually occurs in the pleura (80-90% of all cases), but also other sites, including the peritoneum and pericardium. Patients suffering from asbestos-related mesothelioma may be entitled to compensation.¹

Epidemiology

• It is three times more common in men than women. Often presents between the ages of 40 and 70 years.
• Because of the widespread use of asbestos until the end of the 1970's the incidence of pleural mesothelioma has risen for some decades and is expected to peak between 2010 and 2020.²
• It is associated with occupational exposure to asbestos but only 20% of patients also have pulmonary asbestosis.
• The lag period between initial exposure and death varies but one study found a median latency of 32 years, with 96% of cases occurring after at least 20 years.³ The latent period between exposure and development of the tumour may be up to 45 years.⁴
• The annual number of deaths from mesothelioma had risen from 153 in 1968 to 1848 in 2001, and it is predicted to peak at 1950-2450 cases annually between 2011 and 2015.³

Clinical features

• Malignant mesothelioma should be considered in any patient with a pleural effusion or pleural thickening, especially if a history of asbestos exposure and chest pain is present.³
• Chest pain (typically dull, diffuse, progressive and occasionally pleuritic)
• Breathlessness may be caused by a pleural effusion or circumferential pleural thickening.
• Patients may also present with a palpable chest wall mass
• Weight loss, fatigue, fever, sweats; finger clubbing is usually caused by underlying asbestosis
• Pericardial effusion may be caused by local extension in progressive disease. Ascites caused by peritoneal mesothelioma and secondary hydropneumothorax are uncommon but recognised presentations.
• If the tumour has metastasised there may be lymphadenopathy, hepatomegaly, bone pain, bone tenderness, abdominal pain, gastrointestinal obstruction (peritoneal malignant mesothelioma).

Investigations³

• Chest x-ray and CT scan: may show a pleural effusion, lobulated or nodular pleural thickening, a pleural mass, rib destruction; other features of exposure to asbestos may also be present.
• Pleural fluid: straw coloured or blood stained. Cytological analysis occasionally leads to the diagnosis but a pleural biopsy is usually required.
• Pleural biopsy: ultrasound or computed tomography-guided percutaneous biopsy.
• Thoracoscopy under local anaesthetic (enabling drainage of pleural fluid, pleural biopsy, and pleurodesis) is becoming increasingly available.

Associated diseases

See separate article Asbestos-related Diseases. Inhalation of asbestos fibres can lead to benign pleural disease (pleural plaques, diffuse pleural thickening, atelectasis) parenchymal lung disease (asbestosis) and malignant chest disease (mesothelioma, lung cancer).

Staging

• Stage I: confined inside the capsule of the parietal pleura: ipsilateral pleura, lung, pericardium, and diaphragm.
• Stage II: all of stage I with intrathoracic (N1 or N2) lymph nodes.
• Stage III: local extension of disease into the following: chest wall or mediastinum; heart or through the diaphragm, peritoneum; with or without extrathoracic or contralateral (N3) lymph node involvement.
• Stage IV: distant metastases.

Management

• Symptomatic, as cure is only possible with surgery for extremely localised (stage 1) mesothelioma. Traditional treatment modalities (surgery, radiotherapy, and chemotherapy) have evolved slowly, and there has been little improvement in establishing effective treatments.⁴ Neither radiotherapy nor chemotherapy currently improves survival.
• Surgery:
  • The role of surgery is controversial but extrapleural pneumonectomy and lung-sparing debulking procedures may be considered.
  • Pleurectomy and decortication may provide palliative relief from pain and pleural effusions.
• Chemotherapy:
  • Studies of chemotherapy have shown poor results but promising results have been achieved with pemetrexed and raltitrexed in combination with cisplatin and other combinations, including cisplatin and gemcitabine. Single-agent therapy with vinorelbine may provide useful palliation with low toxicity.⁵
  • The National Institute for Health and Clinical Excellence (NICE) has recommended pemetrexed as a possible treatment for malignant pleural mesothelioma in people:⁶
    • With advanced disease.
    • Whose cancer is not suitable for surgical resection.
    • Who have a World Health Organization (WHO) performance status of 0 (able to carry out all normal activity without restriction) or 1 (restricted in strenuous activity but able to move around and carry out light work).
• Radiotherapy:
  • Prophylactic radiotherapy to the pleural puncture site is often considered in patients who have had large chest wall incisions (during thoracoscopy or insertion of a large-bore chest tube) to reduce the chance of tumour cells seeding along the track to the skin surface.
  • Radiation therapy can also help relieve pain.

Prognosis

• This is difficult to assess because of considerable variation in 'time to diagnosis'.
• Depends on the patient's age, staging information, histology and general 'performance status' at diagnosis, but is generally very poor.
• Median survival is 8-14 months from the time of diagnosis.³ It is almost always fatal.

Document references

1. Department for Work and Pensions; DB1 – A guide to Industrial Injuries Disablement Benefits (August 2009)
2. Boutin C, Schlesser M, Frenay C, et al; Malignant pleural mesothelioma. Eur Respir J. 1998 Oct;12(4):972-81. [abstract]
3. Currie GP, Watt SJ, Maskell NA; An overview of how asbestos exposure affects the lung. BMJ. 2009 Aug 24;339:b3209. doi: 10.1136/bmj.b3209.
4. Pistolesi M, Rusthoven J; Malignant pleural mesothelioma: update, current management, and newer therapeutic strategies. Chest. 2004 Oct;126(4):1318-29. [abstract]
5. Steele JP, Klabatsa A; Chemotherapy options and new advances in malignant pleural mesothelioma. Ann Oncol. 2005 Mar;16(3):345-51. Epub 2005 Jan 27. [abstract]
6. Mesothelioma - pemetrexed disodium, NICE Technology Appraisal (January 2008)

Internet and further reading

• Tan WW; Mesothelioma, eMedicine, Mar 2009
• Khan AN; Asbestos-Related Disease, eMedicine, Mar 2008
• National Cancer Institute (US); Asbestos Exposure and Cancer Risk
• Management of patients with lung cancer, Scottish Intercollegiate Guidelines Network - SIGN (2005)
• Lung cancer - suspected, Prodigy (July 2005)