General Information / Anatomy / Function / Statistics

• Mesothelioma are tumours originating from the lining of the body cavities; this includes the chest and abdomen. Although the most common type of mesothelioma begins within the chest, this cancer should not be confused with lung cancer. Mesotheliomas arise from the serosal lining outside of the lungs within the chest or outside the bowel within the abdomen.
• About 100 new cases of malignant mesothelioma appear in Canada each year
• 30-40 cases are seen at the BC Cancer Agency each year
• Malignant mesothelioma is usually not curable

Symptoms / Signs

• Symptoms and signs from mesotheliomas depend upon location of the mesothelioma, its size and whether it is benign or malignant
• Benign forms of the disease are generally asymptomatic
• The symptomatology of malignant mesotheliomas is due to tumour growth resulting in invasion of surrounding structures and/or the production of fluid (pleural effusion, ascites, or pericardial effusion). Chest pain may be caused by invasion of the chest wall. Pleural effusion causes collapse of adjacent lung and shortness of breath.
• Symptoms of distant spread are possible, but uncommon since the tumour is usually a local problem and blood borne spread is uncommon
• Patients with more advanced disease may be ill generally with fever, night sweats and weight loss
• Involvement of the membrane around the heart (pericardium) may cause heart rhythm disturbances

Etiology / Carcinogens / Risks

• There is a definite association between asbestos and mesothelioma. The risk associated with asbestos exposure has been shown by many investigators and inhalation of asbestos poses the most serious hazard.
• In approximately 30% of mesotheliomas, no asbestos exposure can be traced
• Crocidolite (Cape blue asbestos), the main cancer causing form of asbestos, is associated with over 90% of pleural and peritoneal mesotheliomas. Other types of asbestos fibre have been associated in a less significant way.
• Individuals at highest risk are those employed in the asbestos industry; dockyard workers, especially if they dismantle asbestos-insulated steam piping; those who handle and manufacture asbestos compounds; insulators and steam fitters; and those in demolition and construction industries
• Spouses and children of asbestos workers are also at risk
• The latent interval between exposure to asbestos and development of tumour is long (15-25 years)
• Mesothelioma is not caused by cigarette smoking but asbestos exposure and cigarette smoking both increase the risk of lung cancer

Prevention

• The only method of prevention is avoidance of asbestos exposure
• Cigarette smoking should be avoided by all persons and asbestos exposed individuals should avoid cigarette smoke in particular because asbestos plus cigarette smoking can cause lung cancer

• The chest X-ray is a very helpful test, usually showing thickening of the pleura or pleural effusion in patients with pleural mesothelioma. Sometimes a CT scan of the chest may be required for further information.
• A pleural biopsy is essential for pathological confirmation of the disease. Although pleural fluid cytology may be abnormal, this is often difficult to interpret.
• Patients having peritoneal mesothelioma may require an abdominal surgery for exploration of the peritonial surfaces and biopsy of any lesions observed

Types

• Mesotheliomas may be of epithelial or sarcomatous. Sarcomatous types are more malignant and tend to be resistant to treatment.

Treatment

• Treatment unsatisfactory with no recent advances
• Malignant mesotheliomas are serious illnesses and cure of the disease is rare
• Survival with this type of cancer obviously varies with the extent of the disease, but overall it is in the region of one year

Surgery

• Because of the large area of pleural surfaces, complete surgical removal is rarely technically feasible. The advisability of resection is always considered at diagnosis, but only a small minority of cases are eligible for an attempted resection. Spread of disease to the chest wall, heart, or esophagus often rules out the possibility of an operation.

Radiation

• Radiation may be given for control of symptoms in a localized area. Radiation therapy does not have the power to cure this disease. Radiation cannot be given to the entire tumour because this would involve the treatment of large volumes of normal tissue and the dose of radiation required for tumour control is too high for this to be tolerated. Radiation can, however, be of value in controlling pain in a localized area.

Chemotherapy

• Benefits from chemotherapy treatments for mesothelioma are uncertain as the tumour is often resistant. The best available treatment programs do not have the power to cure any patients with mesothelioma. 20% of patients may have a temporary shrinkage of the disease with currently available drugs.

General Support and Symptom Control

• If pain is associated with mesothelioma, good drug prescriptions are available that can control this. Pleural effusions (fluid build up) can be treated by a small surgical procedure that removes the fluid, permitting re-expansion of the lung and improvement in shortness of breath. Some patients with mesothelioma may have very slow growing tumours and if symptoms are not present, it is often advisable to follow the patient with regular chest X-rays without specific therapy. When symptoms do occur, they should be assessed on an individual basis.
• Chemotherapy may be considered for treatment of recurrent thymoma