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PLEURAL MESOTHELIOMA
Pleural mesothelioma is an aggressive form of cancer that originates in the mesothelial cells lining the pleura, a membrane that covers the lungs and lines the chest cavity. Approximately 75% of all mesotheliomas diagnosed are pleural mesotheliomas. Pleural mesothelioma is most commonly unilateral (on one side of the chest), and occurs most often in men age 60-80 with a history of asbestos exposure, often decades prior to diagnosis.
When pleural mesothelioma begins, it appears as a series of small white nodules which become diffuse, or widespread on the pleural surface. Gradually, these nodules begin to grow together and thicken, forming a “rind” that encases the lung and extends into the fissures or grooves of the pleura and the diaphragm. The tumor spreads by direct invasion of surrounding tissue, inwardly compressing the lung, and outwardly invading the chest wall and ribs.
Pleural Mesothelioma Symptoms
The early symptoms of pleural mesothelioma are not, as a rule, specific enough to cause alarm, and in most cases are attributed to increasing age or overwork. Because of this, it may be several months from the onset of generalized symptoms until the first acute symptom, pleural effusion, occurs. At that time, progressive shortness of breath caused by the effusion, and chest pain caused by chest wall invasion may be in evidence. More general symptoms include dry cough, fatigue, night sweats and weight loss.
Diagnosis of Pleural Mesothelioma
On initial examination by a doctor, 80% to 95% of patients show pleural effusion on x-ray, the rest show little or no fluid. At first, the fluid is free-flowing, and is similar in appearance to that seen in other benign causes or in congestive heart failure, and because of this, these other possibilities are the first to be ruled out in the diagnostic process. Later, the effusion becomes “loculated”, or contained within a boundary in the pleural space, where the fluid does not move.
CT scans are more definitive, and may show not only the effusion, but the presence of pleural masses as well as the size certain lymph nodes; MRI is more sensitive in determining chest wall invasion and spread of disease through the diaphragm; PET may help in staging pleural mesothelioma for possible surgical resection by ruling out extension to the contralateral (opposite) lung or to other distant sites.
Analysis of pleural fluid yields a confirmed diagnosis in a relatively small percentage of patients, and needle biopsy offers only slightly better results. Today, the procedure of choice is the VATS (video-assisted thoracoscopy) procedure, which has a diagnostic yield of >95%, and allows for pleural biopsy, drainage of fluid and pleurodesis. VATS also ensures adequate tissue samples to facilitate a definitive diagnosis.
Pleural Mesothelioma Staging
As with any type of cancer, staging plays a role in what treatment options a pleural mesothelioma patient might be eligible for. Several staging systems are in use, however, the most widely used and most comprehensive is the TNM system associated with the International Mesothelioma Interest Group.
Treatment of Pleural Mesothelioma
Based on a number of factors, several treatment options may be available including surgery, chemotherapy, radiotherapy (or combinations of all three, known as trimodal therapy). The choice of treatment regimen depends largely on the stage of the cancer. Stage I mesothelioma, the least problematic, is treated with surgery to remove the cancerous tissue, unless the patient to too frail to undergo surgery. Sometimes further treatment may not even be conducted in the short term. Of course, both patients who have surgery and those who don’t are monitored closely for future growth of the cancer. The prognosis for people with Stage I mesothelioma can therefore be fairly optimistic. Unfortunately, few patients are diagnosed this early.
Phase IV and metastatic mesothelioma patients have it the worst. Surgery is rarely used on these patients – just chemotherapy as a palliative treatment.
It’s patients in Phases II and III that most often get multimodal treatment combining surgery with chemotherapy or radiation. Patients in hese phases are evaluated for surgery. Those unfit for the rigors of surgery (because of age or ill health) are treated with chemotherapy – multiple services and different regimens if needed. Those judged eligible for surgery often have chemotherapy, too. The oncologist may choose to do a surgical debulking followed by adjuvant chemotherapy and radiation therapy, or to give chemotherapy first (usually the Alimta-Cisplatin combination) and then exploratory surgery. If the surgery points to an unrespectable tumor, some tissue may be removed, but the patient will be further treated with chemotherapy. If the surgeon judges effective removal can be done, a follow-up surgery is schedule where a pleurectomy/decortication of an extrapleural pneumonectomy is conducted. Adjuvant radiation therapy follows pneumonectomies.
Doctors with little experience with this disease might just treat the symptoms with pleural effusion drainage and talc treatment. Specialists at large cancer centers are more likely to suggest trimodal therapy. Second-line therapy for pleural mesothelioma usually involves chemotherapy. Single modality therapies have proved disappointing, so multimodality treatment regimens are often proposed. Although pleural mesothelioma continues to be a difficult cancer to treat, more awareness of the disease, new and better diagnostics, and more successful treatment regimens help to improve its outlook.
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