Mesothelioma cases in WA may have hit a plateau, with a decrease in incidence rates from home renovation exposure indicating the ban on asbestos has worked, new data suggest.

An expert panel reviewed every case of mesothelioma notified to the WA Cancer Registry over the 60 years since the first case was recorded.

The majority of the 2796 cases identified (84.7%) were men. The median age at diagnosis was 70, and the median latency was 47.

Pleural mesothelioma was recorded in almost all cases (93.7%), with the epithelioid subtype being the most prevalent (61.9%).

Overall, median survival was 298 days, and latency was 46 years, which doubled over the study period, according to findings published in Respirology [link here].

More than half of the cases involved workers exposed to manufactured asbestos products (56.9%). Overall, 375 (13.4%) workers from Wittenoom were recorded, and 106 (3.8%) were ex-residents of Wittenoom, a mining town fully closed in 2022 due to asbestos risk.

Non-occupational exposures were proportionally higher in females (52.6%) compared with males (9.5%), with home renovation being the primary exposure in 227 (8.1%) cases. The number of DIY cases and incidence rate ratio peaked in 2005-09 but had since decreased.

This provided some of the first evidence that the asbestos ban in Australia enacted in 1984 might have been successful in reducing exposure to the broader community, said the authors, which included respiratory physician Professor Fraser Brims from Curtin University and Sir Charles Gairdner Hospital.

Findings also showed that median survival increased over the study period from 156 days in 1960-1979 to 360 days in 2010-2020, while the time since first exposure increased from 24 years to 52 years over the same period.

The recorded pathological subtype changed over the study period, with mesothelioma NOS initially accounting for 26.3% of cases but declining to 2.6% in the final decade.

Survival of more than five years was recorded in just 81 (2.9%) patients. Compared with those with shorter survival, long survivors had a higher proportion of females, epithelioid pathology and cases categorised as non-occupational exposures, the authors noted.

“This report provides evidence for the effectiveness of the ban on use of asbestos containing products in Australia with a fall in incidence of DIY/renovation exposure. Whilst mesothelioma remains a disease predominantly of males, there is a clear distinction between sexes in the source of exposure, with the majority of females with non-occupational exposure(s),” they said.

“It should also be noted that over a quarter (n = 111) of mesothelioma in females did not have a clear source of exposure apparent after reviewing the clinical notes. This is likely a reflection of limited exposure history taking and perhaps a lack of appreciation of paraoccupational exposure as an important source, particularly for family members, of exposed workers.”