Written by Ada’s Medical Knowledge Team
What is Mesothelioma?
Mesothelioma is a type of cancer that develops in the layers of tissue that surround the internal organs (the mesothelium). The lining of the lungs (the pleura) is the most commonly affected area, but the cancer can also develop in the tissue in the abdomen that surrounds the digestive organs (the peritoneum), the lining of the heart and the tissue that surrounds the testicles.
Mesothelioma typically develops slowly, manifesting itself in symptoms such as extreme tiredness, fever, shortness of breath, chest pain, a persistent cough, nausea, abdominal pain, swelling or weight loss.
The majority of mesothelioma cases are a result of exposure to asbestos, a once common building material that is now known to be highly toxic. The more exposure to asbestos, the greater the risk of the cancer. Roughly five times more men than women are diagnosed with mesothelioma and around half of all cases occur in individuals 75 years of age or older. It is a fairly rare type of cancer, with around 3,000 reported cases in the USA each year.
There is no known cure for mesothelioma and treatment can be challenging. Life expectancy, therefore, is often limited to between several months and several years after the initial diagnosis.
Symptoms of Mesothelioma
The symptoms of mesothelioma can be difficult to detect due to their similarity the symptoms of other, more common, conditions. Symptoms can also be very slow to develop, making them potentially unnoticeable in the condition’s early stages. In some cases, they can take decades to fully develop.
Symptoms can also differ according to the cancer’s location.
Pleural mesothelioma in the tissue lining of the lungs has symptoms that include:
- Shortness of breath
- Lower back or chest pain
- A persistent cough (especially if coughing up blood)
- Difficulty swallowing
- Fever or sweating (particularly at night)
- Sudden weight loss or lack of appetite
Peritoneal mesothelioma in the abdomen tissue that surrounds the digestive organs has symptoms that include:
- Abdominal swelling and pain
- Breathing difficulties
- Sudden weight loss or lack of appetite
- Constipation or improper bowel function
- Fever or sweating (particularly at night)
Pericardial mesothelioma, a rare form of the condition that develops in the lining of the heart, has symptoms that include:
- Heart palpitations, heart murmurs or an irregular heartbeat
- Difficulty breathing
- Chest pain
- Fever and night sweats
Causes of Mesothelioma
Although there are rare instances where no link can be found, the vast majority of all cases of mesothelioma — some 80 percent — are directly related to exposure to asbestos. The link between asbestos and mesothelioma, therefore, is considered indisputable by healthcare professionals.
Asbestos is a naturally occurring mineral which has been known of since antiquity and mined since the early 19th century, though it was only in the latter half of the 20th century that it became a common building material. Although researchers discovered a link between asbestos and cancer as early as the late 1940s, the extent of its dangers did not become common knowledge until much later and it was only banned in the USA in 1989.
Those with a history of long-term exposure to asbestos are most at risk of being diagnosed with mesothelioma. However, cases have also been reported of mesothelioma in individuals who were only exposed to the material for a relatively short period of time (1-3 months).
Statistically, populations living close to naturally occurring asbestos deposits are at far higher risk of developing mesothelioma than those who do not. Naturally occurring asbestos is found across the globe, including in the United States, Canada and South Africa. Forty percent of the world’s asbestos is mined in Russia, with large amounts also mined in China and Kazakhstan.
When the earth is mined or construction work undertaken, the asbestos is disturbed, releasing particles into the air and exposing large areas to the risk of inadvertent inhalation.
Working with asbestos, particularly in the construction and mining industries, has been proven to vastly increase one’s risk of developing a number of diseases, including malignant mesothelioma. Despite asbestos now being banned, the risk of exposure still exists when dealing with buildings built before the banning order took effect. The use of masks and artificial respiratory systems has been shown to greatly reduce the risks posed.
Due to the symptoms of mesothelioma also being common to less serious conditions, as well as to other pleural and peritoneal malignancies, the cancer can often be difficult to diagnose. Those with a history of exposure to asbestos who display the symptoms should therefore make this clear to their care providers and seek out a doctor specialising in mesothelioma.
Full diagnosis of the cancer can take months, from first identification through initial imaging tests to confirmation through biopsies. Due to the rarity of the disease, patients displaying the symptoms will first be asked to recall their full work history and any exposure to asbestos. Prolonged exposure is grounds for clinical suspicion of mesothelioma and will significantly hasten the diagnostic process.
If an initial chest X-ray shows signs of pleural thickening — a tell-tale sign of mesothelioma — a PET scan, CT scan, MRI, or a combination of the three will follow. These scans give doctors a detailed look inside the body, allowing them to identify the presence of any malignant cancer. If a large amount of fluid is found in the pleural cavity, it is common for doctors to drain the fluid using a syringe and test it for cancerous cells. Though it does not completely exclude the presence of mesothelioma, if no cancerous cells are found, the chances of the disease are greatly reduced.
Like all types of cancer, mesothelioma releases abnormal substances into the bloodstream. While there is no test that can definitively identify these substances and diagnose mesothelioma, various biomarker tests, or assays, are available and can be useful to the diagnostic process.
The presence of malignant mesothelioma can only be fully confirmed with a full biopsy. To do this, a pathologist will examine a tissue sample, or in the case of suspected chest cancer or abdomen cancer, this may involve a thoracoscopy or laparoscopy, respectively. These procedures are types of minimally invasive surgery, wherein surgeons are able to remove a tissue sample through a small incision in the abdomen or chest.
There currently exists no cure for mesothelioma, however there are treatments available that can help prolong life expectancy and improve quality of life. These typically involve a combination of surgery, chemotherapy and radiation therapy. In some cases, emerging or experimental treatments may also be prescribed. The direction that treatment will take is largely determined by the maturity of the cancer, the age and general health of the patient, as well as how far the cancer has spread (this will depend on what stage the cancer has entered – see the prognosis section for more details on the stages of mesothelioma).
If the cancer has been detected early, surgery will involve fully removing the tumor(s) — or, depending on where the cancer is located — the mesothelial lining, lymph nodes or sections of the lungs or heart. However, if the cancer is more developed, this may be impossible and surgery will typically be paired with chemotherapy or radiation therapy — a treatment route that has proven effective in combatting malignant mesothelioma.
Courses of chemotherapy have proven the most effective treatment method in combatting mesothelioma in controlled testing. Chemotherapy drugs work by halting the multiplication of cancerous cells in the body and thereby stopping the spread of the disease and the development of tumors. There are more than 100 types of chemotherapy drugs currently available on the market, with each differentially effective in treating patients in different stages of the disease.
Chemotherapy can result in significant side-effects, most commonly vomiting, stomatitis, exhaustion and diarrhea. Typically, the chemotherapy drugs are administered intravenously in cycles of several weeks followed by a short recuperation break. To lessen the side-effects and more directly target specific tumors, doctors have pioneered a method of localized chemotherapy whereby the drug is injected straight into the tumor itself. While this method has proven effective in combatting early-stage mesothelioma, it is not suitable for tackling the disease once it has spread from its original location.
If the cancer remains localized and the patient is in otherwise good health, radiation therapy, in conjunction with surgery and sometimes chemotherapy as well, can be an effective treatment method. It has been shown to significantly improve a patient’s prognosis, however, it is considered a radical option that can result in serious side-effects. These can include pneumonitis; a condition that involves the inflammation of the alveoli (air sacs) in the lungs that can sometimes be fatal in itself.
If surgery, chemotherapy and radiation therapy prove ineffective, some patients may be eligible for emerging treatments in their clinical trial stage. These treatment options are those that have not yet been approved by the U.S. Food and Drug Administration and are therefore considered experimental.
One such promising treatment method is immunotherapy. This type of treatment harnesses the power of the bodies own immune system, training it to specifically attack the cancerous cells and leave the healthy cells alone. This is done by introducing antigens (substances the body recognises as toxic) into the body, stimulating and improving the immune system’s response to their presence. When used in addition to conventional methods, immunotherapy has seen some success in improving life expectancies.
Across the world, numerous clinical trials are taking place on new drugs for treatment of mesothelioma. These new, cutting-edge drugs promise to advance the treatment of the cancer and improve the prognosis of patients. New drugs take years to be tested and become available on the market, though patients with particularly severe cases may be eligible for inclusion on these clinical trials.
Mesothelioma spreads quickly and is difficult to treat, meaning the prognosis is generally poor. Roughly 50 percent of people with mesothelioma in one location are expected to survive until the first anniversary of their initial diagnosis. Life expectancy after diagnosis, however, depends on a multitude of factors, most significantly the stage at which the cancer is detected and the age of the patient.
People diagnosed with mesothelioma before the age of 50, and women in particular, can expect a better prognosis. Whether the cancer is pleural or peritoneal is also a factor. The prognosis can be improved by maintaining a healthy lifestyle, seeing a mesothelioma specialist and receiving a second opinion.
Long-term survival, however, is rare, with around one in every 10 people surviving for over 5 years after diagnosis.
Doctors generally describe the growth and spread of mesothelioma using the idea of four stages:
- Stage 1: The earliest stage of the cancer when it is still localized to one area of the body, with no spread to the lymph nodes or metastasis. If mesothelioma is detected during this stage the patient has the most treatment options and can expect a higher life expectancy.
- Stage 2: The cancer is still largely localized to one side of the body, but may have spread to the lymph nodes or other organs. Aggressive treatment options may still be an option.
- Stage 3: The cancer is still localized to one side of the body, but has spread further, including to the lymph nodes. Surgical treatment methods become less viable.
- Stage 4: The cancer has conclusively spread to areas far beyond its origin (distant metastases). Treatment at this stage is generally limited to easing the uncomfortable symptoms.
Legal Issues Related to Mesothelioma
Many people have sought to claim compensation for the development of mesothelioma as a result of exposure to asbestos. Since the first in 1929, large amounts of lawsuits and class action cases have been launched, normally against asbestos manufacturers and employers. In the USA, total claims have reached billions of dollars. Despite these precedents in the courts, as yet, the US Congress has passed no federal law on the issue.
Q: What jobs increase the risk of exposure to asbestos?
A: People involved with construction work, demolition and home renovation are at high risk of occupational exposure to asbestos.
**Q: Where is naturally occurring asbestos found? **
A: Naturally occurring asbestos is found in many locations across the world. Asbestos deposits can be found in most US states, with California, Arizona and Virginia having some of the highest levels. People living close to asbestos deposits should take steps to minimize their exposure, such as keeping windows and door closed during strong wind and thoroughly wiping shoes before going indoors.
Q: Can mesothelioma be benign?
A: Yes. Benign mesothelioma - sometimes called multicystic or fibrous mesothelioma - refers to non-cancerous tumors within the pleura. Like malignant mesothelioma, benign mesothelioma also largely results from exposure to airborne asbestos. However, unlike the cancerous version, it is relatively easy to treat with surgery to remove the tumor(s). Benign mesothelioma accounts for a tiny percentage of all mesothelioma cases, making it very rare.
Q: Can mesothelioma be caused by smoking?
A: No. Smoking does not increase the chances of developing mesothelioma. However, exposure to asbestos, like smoking, can also increase the risk of lung cancer.
Q: Is mesothelioma hereditary?
A: No. Unlike most other types of cancer, the only known cause of mesothelioma is exposure to asbestos.
Asbestos. [“Why Isn’t Asbestos Banned in the United States.”] (https://www.asbestos.com/blog/2012/09/17/why-isnt-asbestos-banned-in-the-united-states/) September 17, 2012. Accessed June 21, 2017. ↩
The Mesothelioma Group. [“Mesothelioma Prognosis.”] (https://www.mesotheliomagroup.com/mesothelioma/prognosis/) Accessed June 22, 2017. ↩
American Cancer Society. [“Survival statistics for mesothelioma.”] (https://www.cancer.org/cancer/malignant-mesothelioma/detection-diagnosis-staging/survival-statistics.html) February 17, 2016. Accessed June 22, 2017. ↩
Asbestos Network. “Asbestos and Cigarette Usage Increases Risk of Asbestos lung Cancer.” Accessed June 22, 2017. ↩