The inhalation of asbestos causes lung and pleural cancer, as it has been demonstrated in animal experiments and epidemiological studies.
Malignant mesothelioma is a cancer of mesothelial cells, and affects the pleura and peritoneum in the 80% and 20% of the cases respectively. It usually occurs in people who have been exposed to asbestos in their workplace at least 15 years before the diagnosis, although sometimes the disease has been developed in people with very little to none exposures. In fact, the relationship between malignant mesothelioma and asbestos exposure was first described in 1960 by Wagner and colleagues in South African crocidolite miners.
The incidence of mesothelioma is known in countries where there is a national registry of this disease. Thus, the figure ranges between 14.2 and 2.5 cases per million in men and women, respectively, in the United States, 66 and 7 per million in Australia. In Spain for example there is no record of such occupational diseases. In a study conducted in Catalonia between 1983 and 1990, there was an attributable mortality rate of malignant mesothelioma per 100,000 cases of 0.83 and 0.47 in men and women respectively. In patients living in Barcelona and Cadiz with malignant mesothelioma, 62% of cases could be related to occupational exposure to asbestos, while the remaining 38% could be due to domestic or environmental exposures. The fact that mesothelioma can occur as a result of environmental exposure to asbestos is known, as described in populations living near asbestos mines in areas where the houses were painted with paint containing tremolite or in regions with high amount of the silicate in the soil.
The fiber appears to be associated with this tumor are amphiboles, whereas chrysotile, despite being the most commonly inhaled fibers, seems to be of danger. In Spain, the published series of malignant mesothelioma are concentrated in large cities, since, logically, is where there is a greater industrial exposure to asbestos. Patients usually present with a persistent pleural effusion and a computed tomography is used to reveal pleural lesions that may lead to a correct diagnosis of mesothelioma. This, however, requires pleural biopsy using thoracoscopy that has a yield above 90%.
Malignant mesothelioma invariably progresses to death of patients with a median survival of 7 months. With current evidence, neither radiotherapy nor chemotherapy nor surgery have shown any improvement in the prognosis of these patients. Nowadays new treatments are being tested, as the introduction of intrapleural cytokines, photosensitization mesothelioma cell or gene therapy, with no conclusive results to date. The involvement of patients diagnosed in Spain in research studies of new therapies require cooperation between centers to study a sufficient number of patients.
Pablo Rodriguez is a freelance writer and medical researcher. He has written multiples articles about cancer and spefically mesothelioma. He is currently studying to be a writer at University of Buenos Aires.