Mesothelioma Latency Period
Malignant mesothelioma often has a long period of latency, in fact the longest of the asbestos-related diseases, before a mesothelioma diagnosis occurs in people. Diagnosis happens by mesothelioma doctors when the disease becomes apparent, but latency refers to the length of time it takes from being exposed to asbestos until the time when the disease becomes apparent in a clinical examination. Latency can be as short as 10 years or as long as 50, but the average length of latency for malignant mesothelioma is 35 to 40 years between exposure and diagnosis.Because the latency period for mesothelioma can vary from patient to patient, so too does the age of onset of the disease vary. However, most adult mesothelioma cases are diagnosed in patients between the ages of 40 and into their 60s. Child mesothelioma, while rare, does occur in 2 to 5 percent of malignant mesothelioma diagnoses.
A shorter latency period may occur if a patient has had a higher exposure to asbestos. Many of the people who have a short latency period were exposed to asbestos on the job; this is especially true of people with occupations in shipyards as well as the asbestos and insulation industries.
The typical long latency period of this disease is a contributing factor to a poor mesothelioma prognosis. Most cancers respond much better if they are caught early in their development. Because mesothelioma remains under the surface for typically many years, it is often quite advanced once a diagnosis is made.
Forms of Mesothelioma
The different types of mesothelioma cancer are named based on the parts of the body in which the disease occurs. The three primary mesotheliomas are:Peritoneal mesothelioma is found in the abdomen, while Pleural mesothelioma occurs in the lungs. Pericardial mesothelioma happens in the area of the heart. Where the cancer occurs may also play a part in the latency period; a study showed that 28 years was the average latency period for peritoneal mesothelioma with an average asbestos exposure duration of 5 years, and 35 years latency period with 11 years exposure duration for pleural mesothelioma, but exposure duration could vary widely.
Asbestos Exposure
Exposure to asbestos while on the job appears to be the major cause of mesothelioma. Asbestos was widely used in the United States in the 1960s, and thus the disease tends to become most apparent 30 to 40 years after this, so perhaps the peak of diagnoses in the U.S. will have been between 2000 and 2004. Because laws on exposure to harmful elements while on the job were put into place, it is expected that these statistics will not be on the rise. Australia and Europe may see a peak in 2010 to 2019, and it remains to be seen what will occur in third world countries without the benefit of strong occupational hazard laws in place.The Future
These statistics may be in flux, however, for several reasons. They include:- better health care and better food, people are living longer after retirement
- better occupational exposure regulations, workers are no longer exposed to high levels of asbestos
- better occupational exposure regulations, workers are no longer exposed to high levels of asbestos
- Fewer cases of bronchogenic cancer, which may be fatal in workers exposed to asbestos, before the mesothelioma has made a physical impact
Secondary or limited exposure to asbestos is a contributing factor to the difficulty encountered when trying to figure out exactly when asbestos exposure occurred. However, one of the consequences of the World Trade Center disaster may help researchers to better understand this disease. Because rescue, cleanup, recovery and volunteer personnel were exposed to asbestos along with other airborne contaminants, long-term studies of these people are under way, which may assist researchers in gaining more knowledge about this serious disease.
Sources
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Chahinian, A.P., Pajak, T.F., Holland, J.F. Norton, L., Ambinder, R.M., and Mandel, E.M. Diffuse Malignant Mesothelioma: Prospective Evaluation of 69 Patients. Annals of Internal Medicine. 1982 June. Vol 96 (6 Pt 1), pp. 746-55.
Robinson, B.W., Lake, R.A. Advances in Malignant Mesothelioma. The New England Journal of Medicine. 2005 Oct. Vol 353 (15), pp 1591-603.
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