Mesothelioma is a cancer of the mesothelium, which is a series of thin linings with mesothelial cells. It usually forms near the lungs or abdomen when mesothelial cells become damaged. Mesothelioma is caused by exposure to asbestos, and the cancer takes 15-50 years after exposure to fully form.
Types of Mesothelioma
There are four types of mesothelioma:
- Pleural mesothelioma — Forms in the pleura, a mesothelial lining outside of the lung cavity
- Peritoneal mesothelioma — Forms in the peritoneum, a mesothelial lining around the abdomen
- Pericardial mesothelioma — Forms in the pericardium, a mesothelial lining around the heart
- Testicular mesothelioma — Forms in the mesothelial lining around the testes
Most cases (around 80%) are pleural mesothelioma. Almost all of the rest are peritoneal mesothelioma.
Rates of Mesothelioma in Canada
According to the Canadian Cancer Society, between 400 and 500 people in Canada are diagnosed each year with mesothelioma. The number of cases has increased in Canada in recent years. For instance, in Ontario, the annual case count rose from fewer than 40 in 1982 to nearly 200 by 2012.
Most people with mesothelioma are men. According to the Canadian Cancer Society’s data, around 80% of cases involve men.
Survival From Mesothelioma
Survival from mesothelioma is poor across the world, including Canada. In the United States, the average survival is 1-2 years. In Canada, the five-year survival rate is just 7%.
Factors affecting survival include:
- Stage of cancer
- Eligible treatment options
Similar to other cancers, there are four stages of mesothelioma. They range from least severe (stage 1) to most severe (stage 4). Stage is the biggest factor for survival variances.
According to the Canadian Cancer Society:
- Stage 1 pleural mesothelioma has a median survival of 21-51 months
- Stage 2 pleural mesothelioma has a median survival of 19-26 months
- Stage 3 pleural mesothelioma has a median survival of 15-16 months
- Stage 4 pleural mesothelioma has a median survival of 8-12 months
Unfortunately, most cases are diagnosed in stages 3 and 4, which attributes to the poor life expectancies.
Peritoneal mesothelioma survival in Canada is less known. Canadian Cancer Society reported an average of one year. In the United States, successful surgery for peritoneal mesothelioma from a leading cancer centre can lead to average survival of 3-5 years. The website Mesothelioma Guide reported peritoneal mesothelioma survival averages of 38-42 months.
Causes of Mesothelioma
The primary cause of mesothelioma is asbestos exposure. The mesothelial linings are very narrow, which prevents most dangerous particles and other toxins from reaching the space and affecting the cells.
Asbestos is a flaky mineral used for industrial purposes during the 20th century. Thin, sharp fragments can break apart and contaminate the oxygen for workers, residents and more. Breathing in or swallowing these fragments, or fibres, can lead to them entering a mesothelial lining.
Once in the lining, the asbestos fibre mutates the cells as the body struggles to remove the fibres and control the cells’ quickened duplication.
Exposure to asbestos can occur from residence or occupation, most often the latter. Work settings involved buildings constructed with asbestos, and some jobs even required handling asbestos directly. A few occupations at the highest risk include:
- Ship loading
- Truck driving
- Automobile repair
People who live with or spend time around an asbestos worker could be exposed through their clothes or hair.
Asbestos Ban in Canada
Canada banned asbestos in 2018, when it joined a long list of other countries outlawing asbestos. The government made the decision due to the dangers of asbestos, which can not only cause mesothelioma but also other cancers and deadly health issues.
The Globe and Mail reported in 2014 that asbestos exposure is the top cause of workplace/occupational death in Canada.
The provision is titled “Prohibition of Asbestos and Products Containing Asbestos Regulation.” It prohibits the import, sale and use of asbestos, plus the manufacturing, importing, sale and use of products containing asbestos.
There are some allowances made to “legacy asbestos”, which refers to asbestos present in old buildings, vehicles, planes or equipment. The law also does not apply to asbestos in transit through Canada or most mining residue activities.
Treatments for Mesothelioma
The main treatments for mesothelioma are surgery, chemotherapy and immunotherapy. Health Canada recently approved two immunotherapy drugs, nivolumab and ipilimumab, for mesothelioma cases.
The top surgeries for mesothelioma are:
- Extrapleural pneumonectomy — Removes the affected lung along with the pleura
- Pleurectomy with decortication — Leaves both lungs but removes the entire pleura
- Cytoreduction/Debulking — Removes the peritoneum plus any areas overrun with tumours
- Palliative surgeries — Operations to reduce pain from symptoms
The chemotherapy drugs used for mesothelioma are pemetrexed (Alimta), cisplatin, carboplatin, raltitrexed, vinorelbine and gemcitabine.
The two immunotherapy drugs, nivolumab and ipilimumab, are the generic names for Opdivo and Yervoy. They block immune checkpoints and allow the body’s immune system to fight mesothelioma naturally.
Health Canada approved these drugs for cases not eligible for surgery, which is the first considered option for mesothelioma. The immunotherapy drugs led to an average survival of 18 months, which is better than chemotherapy.
Other treatment options not approved by Health Canada are:
- Photodynamic therapy
- Other immunotherapy drugs
These therapies are used mostly in studies on an experimental basis.
Symptoms of Mesothelioma
The main symptoms of mesothelioma are chest or stomach pain. Chest pain occurs with pleural mesothelioma and stomach pain with peritoneal mesothelioma. This pain is due to fluid packing in the mesothelial linings as room is reduced due to growing tumours and spreading cancer. The lack of room causes fluid to press against the chest wall or stomach.
This effect also causes less room for organs like the lungs to operate fully. This leads to symptoms such as difficulty breathing and persistent coughing.
Other symptoms are:
- Decreased appetite
- Difficulty swallowing
- Mesothelioma Statistics. Canadian Cancer Society. Retrieved from: https://www.cancer.ca/en/cancer-information/cancer-type/mesothelioma/statistics/?region=bc. Accessed: 06/09/2021.
- Health Canada Approves OPDIVO® (nivolumab) plus YERVOY® (ipilimumab) as the First and Only Immunotherapy Treatment for Previously Untreated Unresectable Malignant Pleural Mesothelioma. Cision. Retrieved from: https://www.newswire.ca/news-releases/health-canada-approves-opdivo-r-nivolumab-plus-yervoy-r-ipilimumab-as-the-first-and-only-immunotherapy-treatment-for-previously-untreated-unresectable-malignant-pleural-mesothelioma-837006029.html. Accessed: 06/09/2021.
- Prohibition of Asbestos and Products Containing Asbestos Regulations: frequently asked questions. Government of Canada. Retrieved from: https://www.canada.ca/en/environment-climate-change/services/canadian-environmental-protection-act-registry/prohibition-asbestos-products-regulations-questions.html. Accessed: 06/09/2021.
- Treatments for mesothelioma. Canadian Cancer Society. Retrieved from: https://www.cancer.ca/en/cancer-information/cancer-type/mesothelioma/treatment/?region=on. Accessed: 06/09/2021.
- Mesothelioma. Mesothelioma Guide. Retrieved from: https://www.mesotheliomaguide.com/mesothelioma/. Accessed: 06/09/2021.
For more information on mesothelioma, please visit the Mesothelioma page in our Health Concerns for Patients section.