Mesothelioma is the cancer of the mesothelium - the thin layer of tissue that lines body cavities and organs like the lungs and heart. The cancer is rare, but highly aggressive. Nine out of ten times, it is caused by asbestos exposure. The other 10 percent of cases usually have had suspected but unconfirmed exposure to asbestos.
Asbestos fibers are tiny, and can noticeably be breathed in or swallowed. They lodge themselves in the deepest crevices of the lungs, damaging sensitive tissue, and they can often find their way to the mesothelium. There, they change otherwise normal cells into cancerous ones, inducing mutations that force them to grow uncontrollably and without order. This growth creates a tumor which can eventually kill a patient.
As with any cancer, early detection of mesothelioma is the key to a good prognosis. Unfortunately, in most cases, it is not diagnosed until it reaches its later stages. This is because symptoms often take 20 to 50 years to develop after the initial asbestos exposure. Once symptoms do appear, the cancer has already taken hold, and it is usually too late to do anything - it might already have metastasized (spread to distant regions of the body), and the tumor might not be responsive to chemotherapy. Additionally, mesothelioma mimics other diseases with its symptoms, so the disease is often misdiagnosed. Proper treatments are therefore usually delayed until the diagnosis is corrected.
While there are certainly a few cases of people living relatively long and healthy lives after diagnosis and treatment for mesothelioma, prognoses are generally very poor. According to the American Cancer Society, the five-year survival rate of patients diagnosed with malignant mesothelioma is approximately 10 percent. This rate is only an average, and changes are based on a variety of factors, including what stage the cancer achieved when it was detected and the type and efficacy of the treatments administered.
Age of onset is also an important factor in determining a patient's prognosis. Younger patients tend to be healthier, so they can withstand the stresses that chemotherapy, surgery, and radiation therapy can place on the body. Since they recover quicker and heal faster, more aggressive treatments can be implemented.
The type of mesothelioma that a patient is diagnosed with can also have an affect on his or her prognosis. The most common form of the disease is pleural mesothelioma. In pleural mesothelioma, the cancer is in the lining of the body cavity that surrounds the lungs. Other forms of the disease include peritoneal mesothelioma - where the cancer affects the lining of the lining of the abdominal cavity - and pericardial mesothelioma, the cancer of the lining of the heart. All three of these are equally deadly, but since pleural mesothelioma is the most common, it is the most frequently studied, resulting in more treatments existing for it.
Lastly, cell type appears to have an effect on the life expectancy, and thus the prognosis, of mesothelioma patients. Differently shaped cancerous cells, as determined by a pathologist, seem to have different properties and different consequences for a patient. Epithelioid cells appear to have the best prognoses, while sarcomatoid and biphasic cells have worst ones.