Pleural mesothelioma is a type of cancer that affects the lining of the lungs, otherwise known as the pleura. Caused by exposure to asbestos, pleural mesothelioma is the most common of the three types of mesothelioma, where more than 75% of all diagnosed mesothelioma cases affect the pleura.
The pleura is a sac of soft tissue that contains the lungs as well as a thin membrane known as the mesothelium, which secretes a vital fluid that enables the lungs to expand and contract. While there may be no symptoms present until the later stages of the cancer, first signs of the disease include shortness of breath and chest pain due to the way the cancer affects this area.
The 20 to 50 year latency period between exposure and onset of the disease also accounts for the poor prognosis associated with pleural mesothelioma, which is usually less than 18 months, though this isn’t always the case.
Causes of Pleural Mesothelioma
The primary cause of pleural mesothelioma is asbestos exposure. When inhaled, asbestos fibers become embedded in the lung lining. In time, these sharp fibers irritate the pleural membrane and lead to chronic inflammation and scar tissue.
In individuals who are heavily exposed, 80 percent of whom are older men who worked in industrial jobs, these fibers can lead to the uncontrollable growth of cancerous cells in the pleura, eventually forming tumors.
Following a diagnosis, patients usually exhibit multiple tumor masses affecting both the visceral (further from the lung) and parietal (closer to the lung) surfaces of the pleura. The parietal surface is more often affected than the visceral surface, and the right lung, due to its larger size, often suffers more damage than the smaller left lung. More asbestos tends to settle in the lower lungs than the upper lungs.
These tumors often grow quickly in size and can cover the entire lung cavity, making it very difficult to breathe and causing severe pain. In the advanced stages of pleural mesothelioma, the cancer may spread, or metastasize, to other nearby organs, including the heart, abdomen, and lymph nodes.
Symptoms of Pleural Mesothelioma
Pleural mesothelioma is difficult to diagnose because the symptoms of the disease, if and when present early on, resemble those of other more common illnesses, including the flu, a cold, laryngitis, pneumonia, or whooping cough.
Chest pain and difficulty breathing is usually the first indication of a problem, caused by the growing tumors that enlarge the pleural space and cause it to fill with too much fluid. Such chest pain is often mistaken for heart problems and many yet-to-be-diagnosed mesothelioma victims believe they are having a heart attack or suffering from heart disease. To further complicate diagnosis, symptoms don’t usually develop until stages III or IV of the cancer.
Common symptoms of pleural mesothelioma, caused by the presence of tumors, include:
- Chest, rub, or lower back pain
- Persistent coughing
- Coughing up blood (hemoptysis)
- Difficulty swallowing (dysphagia)
- Shortness of breath (dyspnea)
- Fluid around the lungs (pleural effusion)
- Hoarseness or difficulty speaking
- Blood clots (less common)
The discomfort caused by the above symptoms can also result in:
- Loss of appetite
- Weight loss
It often takes weeks or even months before a correct diagnosis is made, and because the disease usually takes between 20 and 50 years to surface, past exposure to asbestos often doesn’t come to mind when attempting to make a diagnosis or when a patient is giving a medical history. Also, a number of other lung and respiratory diseases, including the flu and pneumonia, have the same symptoms as pleural mesothelioma, making a correct diagnosis even more challenging to confirm.
Ultimately, a definitive diagnosis of malignant pleural mesothelioma is achieved by the use of sophisticated x-rays such as CT scans and MRIs, as well as collecting fluid and tissue biopsies achieved using thoracoscopy, where a doctor can examine the patient’s chest with a small camera. Scans can reveal the presence of pleural effusion and a biopsy, preferably a needle biopsy, can complete the diagnosis. While somewhat uncomfortable, this test is quick and offers a good success rate for accurate diagnosis.
- Chest X-rays are used to detect pleural effusions.
- CT Scans help physicians detect evidence of asbestos exposure.
- PET scans may reveal where the cancer has spread.
- Thoracentesis allow doctors to sample pleural fluid.
- Biopsies are used to collect pleural tissue samples.
After performing a series of the above scans, tests, and biopsies, a treatment plan is the next step.
Because pleural mesothelioma is so difficult to diagnose, the disease is most often in an advanced stage when discovered. That makes mesothelioma treatment options limited. Common treatment options for pleural mesothelioma include:
Only a handful of mesothelioma patients afflicted with this form of the disease are candidates for surgery to remove tumors, especially since the tumors are often large and widespread by the time of diagnosis. Surgical resection may be an option later, if the oncologist thinks the removal of a lung would benefit the patient. Surgical options include pleurectomy/decortication (P/D), where the tumor and diseased pleura are removed, and extrapleural pneumonectomy (EPP), where the pleura, affected lung, diaphragm and pericardium are removed.
More often, pleural mesothelioma patients are treated with radiation or chemotherapy. Chemotherapy involves the use of drugs to both destroy cancer cells shrink tumors. Despite advancements, the success rate of chemotherapy alone is low. A number of clinical trials are attempting to find a combination of chemotherapy drugs that will cure pleural mesothelioma.
Radiation therapy, which is also meant to kill cancer cells and reduce tumor size, is often only successful in managing the symptoms of pleural mesothelioma.
Some doctors opt for what is commonly known as multimodal therapy, which is a combination of two or more therapies, usually chemo and radiation and/or surgery. Most experts agree that a multimodal approach provides the best chances of survival. Recent research has also prompted experimentation with different combinations of chemotherapy drugs, resulting in positive outcomes when certain ones are used at the same time.
Once mesothelioma is diagnosed, it’s important for patients to maintain a healthy lifestyle in order to better combat the disease. This includes proper nutrition, exercise, and stress-relieving therapies.
After a diagnosis and thorough examination of the disease, doctors establish a probable outcome or prognosis, though doing so accurately for pleural mesothelioma is difficult.
Factors that determine prognosis include:
- Patient’s age and gender
- Stage of disease when diagnosed
- Patient’s history of smoking
- Presence of pain when breathing
Currently, the prognosis for those diagnosed with pleural mesothelioma is not good given that diagnosis often occurs in a late, advanced stage. Many patients die within six months of diagnosis; some live up to a year, but survival much beyond that length of time is rare. Clinical trials are constantly underway in hopes of discovering a cure for the disease or a way to further prolong the life of a pleural mesothelioma sufferer.