Doctors usually divide mesothelioma into three types:
- Pleural mesothelioma - affects the pleura, the lining surrounding the lungs. This is the most common form.
- Peritoneal mesothelioma - the cancer attacks the lining of the abdomen, the peritoneum. This is the second most common form.
- Pericardial mesothelioma - the cancer attacks the protective layer covering the heart. This is the rarest form.
Mesothelioma is an aggressive form of cancer. For the majority of patients there is no cure. Doctors usually focus on improving the quality of life as the disease progresses - making the patient as comfortable as possible.
In the United Kingdom, approximately 2,000 patients are diagnosed with mesothelioma annually. According to the CDC (Centers for Disease Control and Prevention), mesothelioma kills over 2,700 people in the USA every year. According to the Mesothelioma register, deaths from this type of cancer rose more than tenfold from 1969 to 2009 in the UK. About four-fifths of all deaths are among men.
What are the signs and symptoms of mesothelioma?A symptom is something the patient feels and describes; while a sign is something other people can see, including doctors and nurses. For example, a symptom may be pain, while a sign could be a rash.
Exposure to asbestos and asbestos dust can take up to thirty years to show symptoms. Often, patients are diagnosed when the disease is already advanced. Outcomes depend on how early the malignancy can be diagnosed.
Mesothelioma signs and symptoms vary, depending on where in the body the cancer is.
Pleural mesothelioma (tissue surrounding the lungs)
- Shortness of breath
- Coughing, often painful
- Unexpected and unexplained loss of weight
- Pain under the rib cage
- Sometimes lumps may be detectable under the skin in the chest area
- Lower back pain
- Discomfort in the side of the chest
- Some people may experience sweating, fever, or difficulty swallowing
- Unexplained weight loss
- Pain in the abdomen
- Swelling in the abdomen
- Lumps in the abdomen
- Nausea, some patients may experience vomiting
- Low blood pressure
- Shortness of breath
- Fluid retention (edema), often in the legs
- Heart palpitations
- Fatigue, extreme after light exertion
- Chest pain
What are the causes of mesothelioma?Experts say that prolonged exposure to asbestos particles is the primary cause of mesothelioma. The risk of developing the disease is closely linked to asbestos particle dosage - i.e. the likelihood of developing mesothelioma is directly proportional to how long a person was exposed, and how much they inhaled.
People in jobs where exposure to asbestos fibers are common have the highest risk of developing the disease. Asbestos was commonly used for insulation, soundproofing, fireproofing, roofing, and ironing board covers.
Industries that may have involved asbestos exposure for some of their workpeople include constructions sites, steel mills, shipyards, oil refineries and power plants.
When the asbestos particles or fibers are inhaled or ingested, they build up in the lining of the abdomen, chest or lungs. This accumulation considerably increases the chances of cancerous cells developing.
When asbestos is damaged and particles or fibers are released into the air, the environment can become hazardous to human health. The fibers can be breathed in or swallowed, they get embedded in tissue, and eventually lead to mesothelioma.
Asbestos is a group of minerals that occur naturally. They exist as fibers or bundles. These fibers may be found in soil or rocks and exist in many parts of the world naturally. Asbestos is made of silicon, oxygen and some other elements.
There are two principle types of asbestos fibers:
- Serpentine asbestos - this is the most common type used in industry. It is known as white asbestos, or chrysotile. The fibers are curly.
- Amphibole asbestos - these include anthophyllite, amosite, actinolite, crocidolite, and tremolite. The fibers are straight, like needles. This type of asbestos, particularly crocidolite, is considered to be more likely to cause cancer. However, even serpentine asbestos has been linked to cancer.
Even family members who never set foot in a working environment that contained asbestos can be exposed. The fibers can be carried home in the workers clothing, and then breathed in by other members of the household.
Asbestos can also be swallowed, as may occur when water flows through asbestos cement pipes. Inhaled asbestos can be coughed up, and then swallowed (when the person swallows the saliva).
WHO (World Health Organization) in 2005 said that approximately 125 million people globally were exposed to asbestos at work in that year, despite their employers having known about the link to cancer and other lung diseases for over six decades. Most work-related exposure today occurs in developing nations.
In much rarer cases, mesothelioma may be linked to irradiation, the inhalation of eronite or some other fibrous silicate, and intrapleural thorium dioxide (Thorotrast - a suspension containing radioactive particles, used in X-ray diagnostics during the 1930s and 1940s, and even in the 1950s in some nations including the USA). Some experts believe that SV40 (simian virus 40) could be involved in the development of the disease.
A new study identifies previously unknown genetic alterations behind mesothelioma - a rare and deadly cancer whose main cause is exposure to asbestos. The findings include some mutations that may serve as new targets for treatment and others that could help improve the diagnosis, screening and prediction of outcomes for patients.
A new study raises hope for the treatment of mesothelioma. It shows that a drug called HRX9 stops tumor growth in mice implanted with human malignant mesothelioma cells.
How is mesothelioma diagnosed?
Digital chest x-ray of advanced malignant mesothelioma (on left)
Biopsy - some tissue is surgically removed so that it can be examined in the laboratory under a microscope. To determine whether a patient has mesothelioma, this will have to be done. How the biopsy is carried out depends on which part of the body is targeted:
Targeting either the chest or abdominal area
- Fine-needle aspiration - a small needle is inserted into the abdomen and chest and some fluid or piece of tissue is removed
- Thoracoscopy - the surgeon inserts a thoracoscope through a small incision between the patient's ribs. A thoracoscope is an endoscope for examination of the chest cavity - it is a tube with a small camera at the end. The surgeon removes a piece of tissue with special tools.
- Thoracotomy - in this surgical intervention, the chest is opened between the ribs so that the surgeon can see the target area and check for signs of cancer. Some tissue may also be removed and sent to the laboratory for testing.
- Laparoscopy - a small incision is made in the abdominal wall, a laparoscope is inserted through the incision into the abdomen, where the surgeon can have a look. The laparoscope is a long tube with a camera at the end. With specialized tools, tissue samples can be removed.
- Laparotomy - the surgeon opens the abdomen and has a look. Sometimes tissue samples may be removed and sent to the lab.
Staging - in medicine, specifically cancer, staging is the process of carrying out tests and examinations to determine the extent of the cancer, how advanced it is, and whether it has metastasized (spread from its original site to other parts of the body).
As soon as mesothelioma has been confirmed (diagnosed), other tests will be ordered to help determine the stage of the cancer. These may include such scans as CT, MRI (magnetic resonance imaging), PET (positron emission tomography), or a chest X-ray. What type of scan is used depends on several different factors.
When all the data is gathered together, the health care professional will assign the cancer a stage. The staging below is for pleural mesothelioma (lungs):
- Stage 1 - the cancer is localized. It is still inside the lining around the lung. It has not spread out.
- Stage 2 - the cancer may have spread to a lung or the diaphragm.
- Stage 3 - the cancer may have reached the lymph nodes, and possibly other parts of the chest
- Stage 4 - the cancer has either spread more extensively in the chest, or may even have reached other parts of the body far from the original site. It may have reached other lymph nodes, or even the brain.
What are the treatment options for mesothelioma?The treatment the doctor will recommend depends on several factors, including:
- Where the cancer is
- The stage of the cancer (how advanced it is)
- The patient's general health and age
If the cancer is very advanced, the tumor(s) can no longer be surgically removed. The only option left, in many cases, is to control the cancer, try to slow down its progress, and focus on making the patient as comfortable as possible.
It is vital that the medical team explains all the options to the patient - including their pros and cons - and if necessary, to his/her loved ones and/or caregivers. Fighting the cancer aggressively may mean enduring very unpleasant side effects, while just focusing on pain and quality of life for the remaining time, might be a better option. This is something the patient needs to discuss thoroughly with the medical team, and perhaps family members or close friends.
Surgery - this means removing tumors by surgery. Surgery is usually only an option during the early stages of the cancer. It may remove the whole cancer, or at least reduce some symptoms and slow it down.
- Fluid accumulation in the lung area - surgery may be recommended if there is fluid accumulation in the chest, resulting in breathing difficulties. The fluid is drained with a tube or catheter. A drug may be injected into the chest to stop a recurrence of fluid build-up. Drugs, such as tetracycline, talc powder, or bleomycin are instilled inside the space between the two layers of tissue lining the lungs (pleura); this causes inflammation, making the two pleura tack together, leaving no space for fluid build-up. Treatment for preventing this type of fluid build-up is called pleurodesis.
- Pleurectomy or peritonectomy - the lining around the lungs or abdominal cavity may be surgically removed. The aim is to relieve mesothelioma symptoms.
- Debulking - removing as much of the tumor as possible, if it is not possible to remove all of it.
- Removing a lung - signs and symptoms may be relieved if the surgeon removes the affected lung and its surrounding tissue. This will be followed by radiotherapy.
Radiotherapy - also known as radiation therapy. For those with pleural mesothelioma, it may help relieve symptoms. Radiotherapy is sometimes administered to prevent metastasis after biopsy or surgery.
Radiation therapy can help relieve symptoms
Clinical trials - human studies using novel treatment methods. The patient should discuss what the trial is about, as well as what to expect realistically, thoroughly with the doctor.
What is the prognosis for mesothelioma?Cancer is a very unpredictable disease, and providing an accurate prognosis is not easy.
In general, prognoses for patients with mesothelioma are not encouraging. Malignant mesothelioma is a very aggressive type of cancer; it also has a long latency period. In the majority of cases, the disease is only detected when it is already in an advanced stage.
In most cases, survival for pleural malignant mesothelioma after diagnosis is no more than one or two years. The patient needs to bear in mind that there are exceptions, and new treatments are being researched and appear all the time.
Written by Christian Nordqvist