That is according to the results of a newly-published study out of Australia, a country with one of the world’s highest rates of asbestos cancer.
To make their determination, mesothelioma researchers reviewed malignant mesothelioma cases from the Western Australian Mesothelioma Registry between 1962 and 2012, comparing each patient’s subtype with their exposure history.
Understanding Mesothelioma Subtypes
Mesothelioma tumor subtypes are determined by subtle differences at the cellular level. Subtype is determined by examining mesothelioma cells under the microscope. Understanding mesothelioma subtypes is an important part of developing effective mesothelioma treatments since the different types respond differently to different therapies and have different prognoses.
Epithelioid mesothelioma is the most common subtype, accounting for as many as 70 percent of all diagnosed mesothelioma cases. Although all varieties of mesothelioma are difficult to treat, epithelioid mesothelioma tends to be the most responsive to conventional treatments.
The least common subtype is sarcomatoid. Mesothelioma tumors made up of spindle-shaped sarcomatoid cells tend to grow and spread the fastest and be hardest to treat. About 10 percent of mesothelioma patients have this subtype.
Biphasic mesothelioma is the second-most common subtype. This type of mesothelioma contains both epithelioid and sarcomatoid cells and makes up about 20 to 30 percent of all mesothelioma cases.
Asbestos Exposure and Subtype
To determine whether a link between subtype and exposure exists, the Australian team considered the total number of days each mesothelioma patient was exposed to asbestos, years since their first exposure, the source of the exposure (occupational or environmental), the form of asbestos (raw or processed) and the type of asbestos.
“There was no strong evidence of a consistent role of asbestos exposure indicators in determining the histological subtype of malignant mesothelioma,” writes lead author Dr. Peter Franklin with the School of Population Health at the University of Western Australia.
The study did find that patients with biphasic mesothelioma were slightly more likely than other subtypes to have been exposed to asbestos at work (as opposed to in their environment) and to have primarily encountered raw fibers.
The findings appear in the newest issue of Occupational and Environmental Medicine.
Franklin, P, et al, “Asbestos exposure and histological subtype of malignant mesothelioma”, August 19, 2016, Occupational and Environmental Medicine, Epub ahead of print