The stage of the mesothelioma cancer, or how far it has progressed at the time of diagnosis, affects life expectancy. The earlier a doctor catches the cancer, the better the prognosis and expected survival rate.

Staging can affect the treatment options available to a patient. Stage I means the cancer is localized, while stage IV, the most advanced stage of mesothelioma, means the cancer has spread and surgery is no longer a viable option. People with mesotheliomas that can be operated on are likely to live longer than those with cancer that has spread too far to be surgically removed. Unfortunately, most patients are not diagnosed until stages III or IV because symptoms can remain unnoticeable for some time.

A large international study looked at the median survival time of patients with pleural mesothelioma(cancer of the lining of the lungs) who were treated with surgery between 1995 and 2009. Patients with stage IV mesothelioma, for example, had a median survival of 12 months, meaning half the patients in the group lived longer than 12 months and half the patients didn�t.