Mesothelioma is a rare but aggressive cancer that arises in the tissue sacs that cover various organs of the body. These thin sacs are made up of mesothelial cells. The most common place for mesothelioma to occur is in the pleura, the sac that covers the lung. Other sites where mesothelioma can arise include the peritoneum, pericardium, and tunica vaginalis.
The principal cause of mesothelioma is occupational or environmental exposure to asbestos. Asbestos is a mineral with physical properties that are good for insulation. This makes it especially useful in the construction, plumbing, and shipbuilding industries. The devastating consequences of asbestos exposure on health went unrecognized for many decades, primarily because there is a very long latency between exposure to asbestos and development of mesothelioma, sometimes up to 50 years. Although asbestos was fi rst reported in the 1960s in a cohort of asbestos miners in South Africa, it was more than a decade before the fi rst governmental regulations were instituted in England and the United States. Many other Western nations followed suit. Despite these regulatory measures, however, asbestos continues to be mined and used for industrial purposes around the world, it lingers in buildings where it was used for insulation, and it remains largely unregulated in many developing countries.
When mesothelioma arises in the pleura, the tumor spreads diffusely over the thin membranous pleural sac. This causes the sac to harden and restrict the patientâ€™s capacity to breath. When the disease is confined to the pleura and does not invade into the fissures or chest wall (defined as very early stage disease), it is possible to do a pleurectomy/ decortication. In this operation, the tumor-containing pleura is stripped from the surface of the lung, removed, and the lung is left in place after the procedure.
It is rare, however, for patients with mesothelioma to have early disease. With more advanced disease, there is invasion of one or more thoracic structures including the lung fissures, chest wall, adjacent mediastinal structures, diaphragm, or pericardium. These patients require an extrapleural pneumonectomy to remove the affected parietal and visceral pleurae, underlying lung, ipsilateral diaphragm, and ipsilateral pericardium. A patch is used to reconstruct the diaphragm and pericardium after the tumor is removed.
All of the standard approaches to treating solid tumors--radiation, chemotherapy, surgery--have been attempted for mesothelioma. None of these approaches is effective when used alone. Surgery combined with adjuvant chemotherapy and radiation (multimodality management), however, has produced signifi cant survival extension (3-14 years) among patients with favorable prognostic factors. Reducing the bulk of the tumor with cytoreductive surgery is key to extending survival. Two surgeries have been developed: pleurectomy/decortication and extrapleural pneumonectomy (shown above). There is a common misperception that these operations are interchangeable. In fact, the selection of operation for a particular patient depends on the size of the patientâ€™s tumor. This is an important consideration, because tumor volume has been linked with survival. Pleurectomy/decortication, which spares the underlying lung, may improve survival but should only be performed in patients with early stage disease with the surgical intent of removing all gross visible tumor (macroscopic complete resection), not simply for palliation. For more bulky, advanced stage tumors, however, sparing the lung at the expense of cytoreduction cannot be recommended. In this circumstance, an extrapleural pneumonectomy should be performed, provided that the patient can tolerate a pneumonectomy (removal of the underlying lung). This is a more extensive operation that involves resection of the parietal and visceral pleurae, underlying lung, ipsilateral diaphragm, and ipsilateral pericardium.
Mesothelioma progresses very rapidly, causing death in about four months without treatment. Therefore, it is important for patients to verify their diagnosis as soon as possible by consulting with a center that has experience in the diagnosis and treatment of mesothelioma.