Mesothelioma is a cancer that starts in the mesothelium, a lining of tissue that protects the internal organs of the body. The different types of mesothelioma help to describe where in the body the cancer originates.
Pleural mesothelioma is the most common of the four mesothelioma types, making up approximately 75% of all cases diagnosed. Unlike other malignant mesotheliomas that occur in the abdomen, heart, or testicles, this form of mesothelioma is a cancer that occurs in the pleura, or the tissue lining of the chest cavity that encloses the lungs.
The pleura consist of two membranes (the visceral and parietal pleurae) that surround the lungs and line the chest wall. Between the two layers, a small amount of fluid provides lubrication.
Causes of Pleural Mesothelioma
Asbestos is the major cause of pleural mesothelioma. How does asbestos trigger this rare and deadly disease?
Asbestos is made up of tiny, needle-like fibers. If these fibers become airborne and are inhaled, they may find their way into the lungs and become embedded in the linings. Once the fibers are lodged in the lung, they are difficult for the body to dislodge. Over time, the asbestos fibers can injure the cells in the lining of the lung and eventually cause pleural mesothelioma.
Individuals exposed to asbestos may live for several decades without developing any mesothelioma symptoms. The latency period of mesothelioma can be anywhere from 20 to 50 years. Due to the long latency period, this form of cancer is often quite advanced when diagnosed, which adds to the difficulty in treating it.
Symptoms of Pleural Mesothelioma
Pleural mesothelioma poses a challenge to diagnose as well as to treat. Indicators of pleural mesothelioma are frequently mistaken for symptoms of minor ailments at first, which can delay diagnosis. The symptoms include the following:
- Persistent cough, usually dry or raspy
- Coughing up blood (hemoptysis)
- Back or chest pain
- Development of lumps under the skin on the chest
- Difficulty swallowing (dysphagia)
- Hoarse voice
- Unexplained weight loss
- Night sweats or feverThese symptoms emerge as a result of tumor growth and the gradual thickening of the pleural membrane in a patient with pleural mesothelioma. The thickening also causes an abnormal buildup of fluid between the pleural tissues of the lung, known as pleural effusion. The fluid presses on the lungs, causing shortness of breath, severe pain, and extreme fatigue.
Pleural Mesothelioma Diagnosis
Making an early diagnosis of mesothelioma is difficult to do because several of its symptoms mimic those of common diseases such as the flu. However, early diagnosis is important because it allows for more treatment options to improve a patient’s overall prognosis and quality of life.
Taking the patient’s symptoms and history of asbestos exposure into consideration, a doctor will conduct a physical exam, take samples of fluid and tissues, and order imaging tests to diagnose pleural mesothelioma. Methods of confirming a diagnosis of pleural mesothelioma may include the use of the following:
Diagnostic Imaging: A patient may undergo imaging tests such as chest X-rays, CT scans, and MRI or PET scans. An X-ray is often the first imaging test ordered and it can help to spot symptoms of pleural mesothelioma such as thickening in the lining of the lungs or fluid buildup. A more detailed picture is provided by a CT or CAT scan, which provides a cross-sectional view of the patient’s body. A CT scan can locate the cancer and show whether it has spread. An MRI uses radio waves and magnets to produce a highly detailed image of the inside of a patient’s body. A PET scan uses radiation to create a 3D color image that can detect cancer and reveal its stage and spread.
Fluid Testing: If a patient has excess fluid in the chest, the doctor may take a sample of the fluid to look for cancer cells under a microscope. This procedure uses a long, hollow needle and is called thoracentesis. If the physician does not find cancer cells, he or she will take a sample of tissue for biopsy to see if the patient has mesothelioma.
Biopsy: A doctor may order a biopsy to collect samples of pleural tissue if fluid testing is inconclusive or if there is no fluid. Two common procedures are needle biopsy and thoracoscopy. In a needle biopsy, the tumor is sampled; in a thoracoscopy, a thin tube with a light and camera is inserted into the patient’s chest, and tools are used to remove a tissue sample.
Cancer can spread to other parts of the body in a process known as metastasis. If a patient receives a diagnosis of mesothelioma, the doctor will conduct tests to determine how far it has spread. Physicians use what is known as “staging” of the disease to indicate the extent to which the tumor has spread and to categorize its size. The staging systems include the Butchart System, the TNM System, and the Brigham System.
Treating the Disease
After diagnosis, the patient and doctor should discuss treatment options, which will take into consideration the patient’s desires, in addition to other factors. Radiation, surgery, and chemotherapy are the most common treatments for malignant mesothelioma.
Radiation can be used internally, within the body, or externally, from outside the body. Radiation can destroy malignant cells, but it is not always seen as the best choice for mesothelioma treatment. Chemotherapy involves the use of drugs to destroy the malignancy. This type of therapy can be used when the disease has spread or has come back after remission. Surgery is a good option if the cancer is caught in an early stage and the tumors can be removed. Often, patients will receive a combination of these treatments as a multimodal attack against this disease.
One kind of surgery, palliative surgery, is used to relieve the pain and discomfort that a patient experiences as he or she battles this disease. Breathing difficulties can be relieved by draining fluid buildup, known as a pleurocentesis, or through injections of drugs or other substances to keep fluid from accumulating, known as pleurodesis. These treatments for pleural mesothelioma can help to prolong a patient’s life, but they do not cure the disease.
Additionally, patients may be interested in seeking alternative treatment methods. These approaches are not approved to cure cancer. However, research has shown that when used in combination with conventional treatments, they can work as a pain or stress relief and often extend a patient’s mesothelioma life expectancy. Some alternative therapies include yoga, Reiki, massage therapy, and pet therapy.
Prognosis for Pleural Mesothelioma
Early detection of pleural mesothelioma is essential and may improve a patient’s life expectancy. If patients are diagnosed with mesothelioma in an early stage, their overall prognosis is better when compared to those in more advanced stages of the disease.
Cancer Research UK shows that only 10% of all pleural mesothelioma cases will survive for 3 years, and 8% will live longer than 5 years. They do mention that some reports quote survival rates of up to 50% after 2 years in patients diagnosed and treated early, proving the range of survival time is very wide. It is important to remember that every cancer case is unique and that these statistics may not accurately mirror an individual’s situation.
While it is difficult to detect the cancer so early due to the lengthy latency period, individuals who have had prior asbestos exposure should tell their doctor and get a physical exam regularly as a precautionary measure.