Cancer of the pleura: mesothelioma

 Cancer of the pleura: mesothelioma
Key messages

The most common form of mesothelioma is malignant pleural mesothelioma, a so-called primary form of cancer of the pleura. 80 to 85% of mesotheliomas are due to exposure to asbestos, which may have occurred several decades before the development of the disease.
 
Exposure to asbestos is mainly of occupational origin, but it can also be environmental (presence of asbestos in certain soils and their surroundings, in particular in rocks of Haute-Corse).
 
 The only recognized risk factor is asbestos. It is classified 1 (certain carcinogen) by the IARC.
 
Certain man-made mineral fibers, exposure to ionizing radiation, the SV40 virus, or chemicals such as bromates, nitrosoureas, or nitrosamines, are suspected risk factors for mesothelioma.
 
Tables of occupational diseases No. 30 (general scheme) and 47 (agricultural scheme) provide for compensation for patients who have been exposed to asbestos during their professional activity. In the event of recognition as an occupational disease, the worker benefits from a right to terminate his activity early from the age of 50, and compensation from the FIVA.
 
Improving the observation and monitoring of cancers linked to the professional environment is one of the measures of the 2009 - 2013 cancer plan. By decree n ° 2012-47 of January 16, 2012, mesotheliomas are added to the list. official reportable diseases.
General information on mesothelioma
Asbestos as the main cause
Other debated risk factors
Compensation as an occupational disease
Strengthened public health policies
 

General information on mesothelioma


Mesothelioma is a rare malignant tumor that affects the cells of the mesothelium, a protective membrane that covers most of the internal organs of the body including the pleura, peritoneum and pericardium.
Its most common form is malignant pleural mesothelioma. This is a so-called primary form of cancer of the pleura, which is characterized by an increase in cancer cells in the tissue that makes up the pleura. The pleura is a membrane that envelops the lungs, made up of two layers, one covers the lungs (inner layer or visceral pleura), the other covers the inside of the chest cavity (outer layer or parietal pleura). When the disease occurs, the pleura thickens, takes on a scalloped appearance and the space between these two layers (pleural cavity) can fill with fluid and cause breathing difficulties.

An estimated 906 new cases of cancer of the pleura in 2005 in France, 71% of which occur in men. Six in 10 new cases are diagnosed in people over the age of 69. The most recent data show 1090 deaths per year.

Asbestos as the main cause
80% to 85% of mesotheliomas are linked to exposure to asbestos, mainly of occupational origin, but also environmental. This exposure may have occurred several decades before the disease developed. Multiple parameters influence the onset of mesothelioma:

the time elapsed from the start of the exposure
the cumulative dose of asbestos: it is expressed in fibers per milliliter (mL) of air multiplied by the number of years of exposure for occupational exposures, and in fibers per liter of air multiplied by the number of years of exposure for exposures of the general population;
peak exposure;
the size and geometry of the fibers that determine the penetration of asbestos into the respiratory tract and their biopersistence: the most harmful fibers correspond to a length greater than 5 micrometers (μm) and a diameter of less than 0.5 μm
Asbestos is the only recognized risk factor for mesothelioma of the pleura (classified as group 1, certain carcinogen by the IARC); apart from erionite, a natural mineral fiber of the zeolite family, which is also a recognized risk factor, which is only present in certain regions of Turkey.

The occurrence of mesothelioma, in the absence of exposure to asbestos, is also possible (it affects about one person in a million).

Other debated risk factors
Other potential factors are mentioned and need to be confirmed: certain artificial mineral fibers such as refractory ceramics, exposure to ionizing radiation, to the SV 40 virus or to chemical agents such as bromates, nitrosoureas, nitrosamines.

The role of individual genetic susceptibility factors is likely, but no gene predisposing to mesothelioma has been identified. Unlike lung cancer, exposure to tobacco has not been demonstrated in the risk of developing mesothelioma.