Risk for Peritoneal Mesothelioma Keeps Rising Decades After Exposure

Pleural mesothelioma risk may level off over several decades, but the risk for peritoneal mesothelioma never goes down.

That is the conclusion of researchers at Italy’s University of Eastern Piedmont. It is based on data from more than 50,000 asbestos-exposed Italian workers.  

More than 40 years after asbestos exposure, the workers’ risk for peritoneal mesothelioma continued to rise.

Calculating Mesothelioma Rates Over Time

Asbestos is the primary cause of all types of malignant mesothelioma. Even short-term asbestos exposure raises the risk for peritoneal mesothelioma and pleural mesothelioma.

Peritoneal mesothelioma occurs in the lining of the abdomen. Pleural mesothelioma tumors start on the lining around the lungs. 

If asbestos fibers are inhaled or swallowed, they embed themselves in these linings. This causes inflammation and irritation that can trigger mesothelioma decades later. 

But some studies suggest that the risk for peritoneal mesothelioma or pleural mesothelioma may eventually taper off. Some scientists think this may be because the body gradually rids itself of the toxic fibers. 

Measuring Risk for Peritoneal Mesothelioma

The Italian researchers wanted to test the tapering off theory. They collected data from 43 groups of asbestos-exposed workers. The groups represented a total of 51,801 people. 

Starting with the “time since first exposure” (TSFE), the researchers analyzed the data in two ways. First, they applied a traditional risk model called the mesothelioma multistage model. 

Then they created a computer model of what mesothelioma rates might look like if the body cleared out asbestos fibers over time. The results revealed a clear difference between long-term risk for peritoneal mesothelioma and pleural mesothelioma.

“Rates of pleural cancer increased until 40 years of TSFE, but remained stable thereafter,” write the researchers.  

But the risk for peritoneal mesothelioma did not level off. Asbestos-exposed workers were even more likely to get peritoneal mesothelioma 60 years after exposure than they were at 20 years. 

Asbestos Fibers and Mesothelioma Incidence

The Italian team concludes that pleural mesothelioma risk eventually plateaus but the risk for peritoneal mesothelioma never does. They say the pleural rates fit the model of a gradual elimination of asbestos fibers over time. 

Regardless of whether mesothelioma risk levels off, asbestos-exposed people cannot afford to let their guard down. Doctors say every person exposed to asbestos should know the signs of mesothelioma and have regular checkups. 

Some studies have also suggested that low-dose CT scans may help catch mesothelioma earlier. 

Source: 

Barone-Adesi, F, et al, “Role of asbestos clearance in explaining long-term risk of pleural and peritoneal cancer: a pooled analysis of cohort studies”, September 2019, Occupational and Environmental Medicine, pp. 611 – 616, https://oem.bmj.com/content/76/9/611