Mesothelioma – the cancer of the outer surface of some of the body’s organs
Mesothelioma is a type of cancer that develops in the lining that covers the outer surface of some of the body’s organs. It’s usually linked to asbestos exposure.
Mesothelioma mainly affects the lining of the lungs (pleural mesothelioma), although it can also affect the lining of the tummy (peritoneal mesothelioma), heart or testicles.
More than 2,600 people are diagnosed with the condition each year in the UK. Most cases are diagnosed in people aged 60 to 80, and men are affected more commonly than women.
Mesothelioma is a type of rare cancer that develops in the mesothelium-a thin layer of tissue that surrounds many of the internal organs such as the lungs, heart and testis. A cancerous tumor of the mesothelium is called a malignant mesothelioma, but is generally referred to as mesothelioma. It is an aggressive form of cancer.
More than 80% of mesothelioma cases are caused by exposure to asbestos. Exposure to asbestos leads to asbestosis, a chronic respiratory disease where the inhaled asbestos fibers cause lung scarring and stiffness of the lungs. Asbestosis prevents the patients from taking full and deep breaths. It is not a cancer but the patients with asbestosis more likely develop lung cancer and mesothelioma. Asbestosis develops from the lodging of asbestos fibers in the alveoli / air sacs of the lungs whereas mesothelioma develops from the asbestos fibers lodged in the lining of the lungs.
Unfortunately, it’s rarely possible to cure mesothelioma, although treatment can help control the symptoms.
According to the National Asbestos Profile of India by The Occupational and Environmental Health Network of India (OEHNI) published on April 28, 2017, fifty five countries have banned the use, trade, import, mining, manufacturing and other economic activities related to asbestos. In spite of adequate evidence about the role of asbestos in mesothelioma, India is one of world’s largest importers of asbestos. In 2014-15, India has imported over 396,493 tons and by 2017, it is expected to rise by 605,000 tons with 9% growth. During 2009-2012, 21 cases of mesothelioma were reported at the Gujarat Cancer Research Institute, Ahmedabad while in 2013, in just one year, 23 cases of mesothelioma were diagnosed.
What are the Types of Mesothelioma?
Mesothelioma can be divided into different types on the basis of its location, types of cells involved and the presence of malignancy.
a) Mesothelioma type by location: The most common way to classify mesothelioma is based on the location of the cancer.
- Pleural mesothelioma– This is the most common type and develops in the lining of the lungs (known as the pleura). It is hard to diagnose.
- Peritoneal Mesothelioma-It originates in the lining of the abdomen and often spreads to abdominal organs, including the spleen, liver and bowel.
- Pericardial Mesothelioma– It is rare (less than 1%) and originates in the lining of heart (the pericardium).
- Testicular Mesothelioma-It is an extremely rare form of the disease, with less than 100 cases having been diagnosed around the world.
b) On the basis of cell types:
- Epithelial mesothelioma- It is the most prevalent type responsible for approximately 75% of diagnosed cases. The cells are uniform in shape with an elongated pattern. Epithelial mesotheliomas have the best outcomes.
- Sarcomatoid mesothelioma– It is a less common type of mesothelioma and the cells are long, spindle-shaped, arranged in a haphazard way and grow out of supportive structures, such as bones and muscles.
- Biphasic / Mixed mesothelioma– It consists of a mix of epithelial and sarcomatoid cell types.
- Malignant Mesothelioma– Most forms of mesothelioma are malignant, making the disease, as a whole, very deadly.
- Benign Mesothelioma– It is very rare and well-differentiated papillary mesothelioma (WDPM) is one of the examples of benign mesothelioma.
Symptoms of mesothelioma
The symptoms of mesothelioma tend to develop gradually over time. They typically don’t appear until several decades after exposure to asbestos.
Symptoms of mesothelioma in the lining of the lungs include:
- chest pain
- shortness of breath
- fatigue (extreme tiredness)
- a high temperature (fever) and sweating, particularly at night
- a persistent cough
- loss of appetite and unexplained weight loss
- clubbed (swollen) fingertips
Symptoms of mesothelioma in the lining of the tummy include:
- tummy pain or swelling
- feeling or being sick
- loss of appetite and unexplained weight loss
- diarrhoea or constipation
See your GP if you have any persistent or worrying symptoms. Tell them about any exposure to asbestos you may have had in the past.
What causes mesothelioma?
Mesothelioma is almost always caused by exposure to asbestos, a group of minerals made of microscopic fibres that used to be widely used in construction.
These tiny fibres can easily get in the lungs, where they get stuck, damaging the lungs over time.
It usually takes a while for this to cause any obvious problems, with mesothelioma typically developing more than 20 years after exposure to asbestos.
The use of asbestos was completely banned in 1999, so the risk of exposure is much lower nowadays. But materials containing asbestos are still found in many older buildings.
What are the Causes of Mesothelioma?
Generally, when asbestos fibers are inhaled, they get lodged in the lining of the lungs or the heart. They enter the abdomen when they are cough up from the lungs and swallowed. They cause inflammation that finally leads to the development of mesothelioma.
Asbestos is a generic name for six types of silicate minerals that share common properties. Asbestos can cause DNA damage both directly as well as indirectly. Asbestos impedes the process of mitotic cell division leading to cellular damage and mutation. Further, asbestos also causes mesothelial cells to release reactive oxygen and nitrogen species, the agents that also cause mutation.
Usually, it takes 10-50 years for mesothelioma to develop after the asbestos exposure. This is one of the reasons why mesothelioma cases continue to appear in the countries even where asbestos has been banned. However, in few cases, the latency period is quite shorter and this is supported by the findings of mesothelioma in children and young teenagers.
In 80% of the cases, asbestos exposure is the cause of mesothelioma. However, recent studies have shown the role of certain environmental risk factors contributing to mesothelioma symptoms. In 2016, the case of a 60-year-old patient with mesothelioma without any prior exposure to asbestos has been reported.
- Asbestos-like minerals: Other silicate minerals such as Erionite, a form of zeolite, in particular has been associated with mesothelioma.
- Simian Virus 40 (SV40): A number of studies have reported association of SV40 with mesothelioma leading to the speculation that SV40 may contribute to the development of mesothelioma, though it does not appear to cause mesothelioma on its own.
- Smoking: Individuals who smoke and are exposed to asbestos are at a much higher risk.
- Radiation Exposure: In few cases, mesothelioma is caused by radiation exposure.
- Carbon Nanotubes: Some researchers have reported carbon nanotubes, and other high aspect ratio nanoparticles (HARNs), as potential causes of mesothelioma.
In its early stages, mesothelioma does not have many symptoms. Most of the symptoms are caused by the growing cancer and the pressure it exerts on a nerve or other body organ.
The symptoms of pleural mesothelioma are persistent cough, tiredness, chest pain, loss of appetite, shortness of breath, sweating and high temperatures, losing weight, difficulty in swallowing, a hoarse or husky voice, and in some cases, changes in the shape of the fingers and nails (known as finger clubbing).
The symptoms of peritoneal mesothelioma are abdominal swelling, lumps in the abdomen, pain in the abdomen, poor appetite, diarrhea or constipation and unexplained weight loss.
Patients suffering from pericardial mesothelioma experience difficulty in breathing and chest pain whereas mesothelioma of testis can be first detected as swelling or a mass on a testicle.
How mesothelioma is diagnosed
If your GP suspects mesothelioma, they’ll refer you to a hospital specialist for some tests.
A number of different tests may need to be carried out, including:
- an X-ray of your chest or tummy
- a CT scan – a number of X-ray images are taken to create a detailed image of the inside of the body
- fluid drainage – if there’s a build-up of fluid around the lungs or in the tummy, a sample may be removed using a needle inserted through the skin so the fluid can be analysed
- a thoracoscopy or laparoscopy – the inside of your chest or tummy is examined with a long, thin camera that’s inserted through a small cut (incision) under sedation or anaesthetic; a sample of tissue (biopsy) may be removed so it can be analysed
These tests can help diagnose mesothelioma and show how far it’s spread.
Patients with the above symptoms should visit a doctor. The diagnostic tests consist of imaging tests, blood tests and biopsies.
Imaging tests: Usually the first step in making a mesothelioma diagnosis involves X-ray imaging. X-rays detect fluid accumulation caused by the mesothelioma. CT scan is more conclusive than x-rays as CT scans can determine the location of tumors allowing doctors to take a biopsy and make a definite diagnosis. Mesothelioma cells appear as bright spots on a PET scan making this scan useful to determine the extent of spread of the cancer to other sites. An MRI scan is useful to determine the damage to tissue surrounding the tumor and in diagnosing peritoneal mesothelioma.
Blood tests: These tests look for the presence of biomarkers which are found to be elevated in people with mesothelioma. The biomarkers that may be measured include:
- Soluble mesothelin related peptides (SMRP)
- Megakaryocyte potentiation factor (MPF), which is produced by a mesothelin precursor protein
- Cancer Antigen 125 (CA125)
- Fibulin-3. Although it is still in the early testing stages, this promising new biomarker could serve as an early warning in patients with mesothelioma. Fibulin-3 is a protein found in plasma which indicates the presence of mesothelioma.
In addition, the measurement of biomarkers such as osteopontin, interleukin-6 (IL-6), mesothelin, 8-hydroxy-2′-deoxyguanosine (8OHdG), vascular endothelial growth factor-beta (VEGF-β), and estrogen receptor beta (ERβ) also have proven to be useful in detecting mesothelioma or monitoring the effectiveness of treatment.
Biopsies: These tests can reveal whether a growth is cancerous, where in the body the cancer originated and what type of cells are involved. There are several ways by which biopsies are performed such as fine-needle aspiration, incisional/core and excisional biopsy. The biopsy may be performed through procedures like a thoracoscopy or a mediastinoscopy.
Immunohistochemistry: The presence of markers such as calretinin, podoplanin (PDPN), EMA (epithelial membrane antigen) in a membranous distribution, mesothelin, WT1 (Wilms’ tumour 1), cytokeratin, HBME-1 (Human mesothelial cell), or osteopontin in the biopsy sample could suggest the presence of mesothelioma.
The analysis of pleural fluid is usually not useful in the diagnosis of mesothelioma.
Staging of mesothelioma is based on the recommendation by the International Mesothelioma Interest Group and is staged I–IV based on the TNM status.
Treatments for mesothelioma
The best treatment for mesothelioma depends on several factors, including how far the cancer has spread and your general health.
As mesothelioma is often diagnosed at an advanced stage, treatment is usually focused on controlling the symptoms and prolonging life for as long as possible.
This is known as palliative or supportive care.
Possible treatments include:
- chemotherapy – this is the main treatment for mesothelioma and involves using medicine to help shrink the cancer
- radiotherapy – this involves using high-energy radiation to kill cancer cells; it may be used to slow the cancer down and keep it under control
- surgery – an operation to remove the cancerous area can be done if mesothelioma is detected at a very early stage, although it’s not clear whether surgery is helpful
You’ll also probably have treatment for your individual symptoms to help you feel as comfortable as possible.
For example, regularly draining fluid from your chest may help your breathing and strong painkillers may help relieve your pain.
Sometimes a procedure is carried out to stop the fluid coming back again by making the outside of the lungs stick to the inside of your chest (pleurodesis), or a tube is put in your chest to drain the fluid regularly at home.
Your doctors should discuss these treatments with you.
It is quite challenging to treat mesothelioma patients. The important factors determining a mesothelioma treatment plan include the primary site affected, the cell type of the cancer, whether the cancer is localized to the chest or has spread to the chest wall, diaphragm, or lymph nodes, as well as the age and overall health of the patient.
The approaches currently used for the treatment are chemotherapy, and multimodal treatment. Multimodal treatment generally consists of a primary treatment (surgery to remove the tumor) used in combination with a neoadjuvant therapy (radiation to shrink the tumor size) and an adjuvant treatment (chemotherapy to kill any remaining cells). In various studies, multimodal treatment has been shown to be more effective than any of the individual treatments alone.
Surgery: For patients with an early-stage mesothelioma diagnosis, surgery can be used to remove the mesothelial lining, one or more lymph nodes, or part or all of a lung or other organ. Sometimes, it works as palliative as it relieves the symptoms of mesothelioma, without aggressively treating the disease. In pleurectomy / decortication, the pleura is removed along with the cancers, while in extrapleural pneumonectomy, the lung and pleura are removed along with other affected parts.
Radiotherapy: The efficacy of this treatment is limited as irradiation with a high radiation dose to an extensive tumor area can cause severe adverse effects such as pneumonitis, myocarditis, and myelopathy due to spinal cord toxicity. It is therefore mostly used for palliative purposes or in combination with surgery.
Photodynamic (PDT) therapy: It is a light-based cancer treatment which requires the interaction of a photosensitizer, oxygen, and light and these three together induce a tumoricidal photochemical reaction. Recently, it was shown that PDT offers an improved survival but it has to be confirmed by a randomized clinical trial.
Chemotherapy: Cisplatin and pemetrexed, an antifolate combination chemotherapy are the current preferred treatment for mesothelioma. Gemcitabine can be combined with pemetrexed in patients who cannot take cisplatin. Other combinations that have been tried out include cisplatin/doxorubicin/mitomycin C, bleomycin/intrapleural hyaluronidase, cisplatin/doxorubicin, carboplatin/gemcitabine, and cisplatin/vinblastine/mitomycin C.
Immunotherapy: This type of treatment is more specific and targeted than the chemotherapy and spurs the patient’s own defenses to fight the cancer.
Recently, it was observed that two young women with papillary peritoneal mesothelioma with widespread recurrence received platinum-pemetrexed chemotherapy along with apitolisib, a dual phosphoinositide 3-kinase-mammalian target of rapamycin (PI3K-mTOR) inhibitor. Both the patients are alive and well 10–13 years after the diagnosis. This study identifies the use of targeted therapies with PI3K-mTOR-based inhibitors as a novel approach, warranting further clinical assessment.
Other immunotherapy drugs that show promise in the treatment of mesothelioma are pembrolizumab, tremelimumab, bevacizumab and atezolizumab.
Outlook for mesothelioma
Unfortunately, the outlook for mesothelioma tends to be poor. This is because it doesn’t usually cause any obvious symptoms until late on and can progress quite quickly once it reaches this stage.
- around half (50%) of people with mesothelioma will live at least a year after diagnosis
- around 1 in every 10 people (10%) with mesothelioma will live at least 5 years after diagnosis
There are currently around 2,500 deaths from mesothelioma each year in the UK. This number is expected to drop in the future because asbestos was banned in 1999.
More information and support
If you’d like to find out more about mesothelioma, the following organisations can provide further information, advice and support:
If you (or a relative) was exposed to asbestos in the UK, you may by entitled to a payment as part of a government run assistance scheme:
A similar scheme is also available for people who were exposed to asbestos while serving in the armed forces:
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