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 theinternal organs (the mesothelium). The lining of the lungs (the pleura) is the most commonlyaffected area, but the cancer can also develop in the tissue in the abdomen that surroundsthe digestive organs (the peritoneum), the lining of the heart and the tissue that surroundsthe testicles. 1
Mesothelioma typically develops slowly, manifesting itself in symptoms such as extremetiredness, fever, shortness of breath, chest pain, a persistent cough, nausea, abdominalpain, swelling or weight loss. 2
The majority of mesothelioma cases are a result of exposure to asbestos, a once commonbuilding material that is now known to be highly toxic. The more exposure to asbestos, thegreater the risk of the cancer. Roughly five times more men than women are diagnosed withmesothelioma and around half of all cases occur in individuals 75 years of age or older. Itis a fairly rare type of cancer, with around 3,000 reported cases in the USA each year. 3
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 initialdiagnosis.
Symptoms of Mesothelioma
The symptoms of mesothelioma can be difficult to detect due to their similarity the symptomsof other, more common, conditions. Symptoms can also be very slow to develop, making thempotentially unnoticeable in the condition’s early stages. In some cases, they can takedecades 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 theheart, 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 casesof mesothelioma — some 80 percent — are directly related to exposure to asbestos. The linkbetween asbestos and mesothelioma, therefore, is considered indisputable by healthcareprofessionals.
Asbestos is a naturally occurring mineral which has been known of since antiquity and minedsince the early 19th century, though it was only in the latter half of the 20th century thatit became a common building material. Although researchers discovered a link between asbestosand cancer as early as the late 1940s, the extent of its dangers did not become commonknowledge until much later and it was only banned in the USA in 1989. 4
Those with a history of long-term exposure to asbestos are most at risk of being diagnosedwith mesothelioma. However, cases have also been reported of mesothelioma in individualswho 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 farhigher risk of developing mesothelioma than those who do not. Naturally occurring asbestosis found across the globe, including in the United States, Canada and South Africa. Fortypercent of the world’s asbestos is mined in Russia, with large amounts also mined in Chinaand Kazakhstan.
When the earth is mined or construction work undertaken, the asbestos is disturbed, releasingparticles into the air and exposing large areas to the risk of inadvertent inhalation.
Working with asbestos, particularly in the construction and mining industries, has beenproven to vastly increase one’s risk of developing a number of diseases, including malignantmesothelioma. Despite asbestos now being banned, the risk of exposure still exists whendealing with buildings built before the banning order took effect. The use of masks andartificial 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 wellas 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 makethis 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 initialimaging tests to confirmation through biopsies. Due to the rarity of the disease, patientsdisplaying the symptoms will first be asked to recall their full work history and anyexposure to asbestos. Prolonged exposure is grounds for clinical suspicion of mesotheliomaand 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 anymalignant cancer. If a large amount of fluid is found in the pleural cavity, it is commonfor doctors to drain the fluid using a syringe and test it for cancerous cells. Though itdoes 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 diagnosemesothelioma, various biomarker tests, or assays, are available and can be useful to thediagnostic process.
The presence of malignant mesothelioma can only be fully confirmed with a full biopsy. Todo this, a pathologist will examine a tissue sample, or in the case of suspected chest canceror abdomen cancer, this may involve a thoracoscopy or laparoscopy, respectively. Theseprocedures are types of minimally invasive surgery, wherein surgeons are able to remove atissue sample through a small incision in the abdomen or chest.
There currently exists no cure for mesothelioma, however there are treatments availablethat can help prolong life expectancy and improve quality of life. These typically involvea combination of surgery, chemotherapy and radiation therapy. In some cases, emerging orexperimental treatments may also be prescribed. 5 The direction that treatment will takeis largely determined by the maturity of the cancer, the age and general health of thepatient, as well as how far the cancer has spread (this will depend on what stage the cancerhas 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 sectionsof the lungs or heart. However, if the cancer is more developed, this may be impossible andsurgery will typically be paired with chemotherapy or radiation therapy — a treatment routethat has proven effective in combatting malignant mesothelioma.
Courses of chemotherapy have proven the most effective treatment method in combattingmesothelioma in controlled testing. Chemotherapy drugs work by halting the multiplicationof cancerous cells in the body and thereby stopping the spread of the disease and thedevelopment of tumors. 6 There are more than 100 types of chemotherapy drugs currentlyavailable on the market, with each differentially effective in treating patients in differentstages 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, radiationtherapy, in conjunction with surgery and sometimes chemotherapy as well, can be an effectivetreatment 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 includepneumonitis; a condition that involves the inflammation of the alveoli (air sacs) in thelungs that can sometimes be fatal in itself.
If surgery, chemotherapy and radiation therapy prove ineffective, some patients may beeligible for emerging treatments in their clinical trial stage. These treatment options arethose that have not yet been approved by the U.S. Food and Drug Administration and aretherefore considered experimental.
One such promising treatment method is immunotherapy. This type of treatment harnesses thepower of the bodies own immune system, training it to specifically attack the cancerouscells and leave the healthy cells alone. This is done by introducing antigens (substancesthe body recognises as toxic) into the body, stimulating and improving the immune system’sresponse to their presence. When used in addition to conventional methods, immunotherapyhas seen some success in improving life expectancies.
Across the world, numerous clinical trials are taking place on new drugs for treatment ofmesothelioma. These new, cutting-edge drugs promise to advance the treatment of the cancerand improve the prognosis of patients. New drugs take years to be tested and becomeavailable on the market, though patients with particularly severe cases may be eligiblefor inclusion on these clinical trials.
Mesothelioma spreads quickly and is difficult to treat, meaning the prognosis is generallypoor. Roughly 50 percent of people with mesothelioma in one location are expected to surviveuntil 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 canceris detected and the age of the patient.
People diagnosed with mesothelioma before the age of 50, and women in particular, can expecta better prognosis. Whether the cancer is pleural or peritoneal is also a factor. The prognosiscan be improved by maintaining a healthy lifestyle, seeing a mesothelioma specialist andreceiving a second opinion. 7
Long-term survival, however, is rare, with around one in every 10 people surviving for over 5 years after diagnosis. 8
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 ofthe body, with no spread to the lymph nodes or metastasis. If mesothelioma is detectedduring this stage the patient has the most treatment options and can expect a higher lifeexpectancy.
- Stage 2: The cancer is still largely localized to one side of the body, but may havespread to the lymph nodes or other organs. Aggressive treatment options may still be anoption.
- 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 (distantmetastases). Treatment at this stage is generally limited to easing the uncomfortablesymptoms.
Legal Issues Related to Mesothelioma
Many people have sought to claim compensation for the development of mesothelioma as a resultof exposure to asbestos. Since the first in 1929, large amounts of lawsuits and class actioncases have been launched, normally against asbestos manufacturers and employers. 9 In theUSA, 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 doors 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. 10 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 11.
Q: Is mesothelioma hereditary?
A: No. Unlike most other types of cancer, the only known cause of mesothelioma is exposure to asbestos. 12