China has a unique prevalence of different mesothelioma types and an unusual incidence of the disease in women, according to a research letter published in JAMA Oncology.
The research letter, titled, “Association of Asbestos Exposure With Malignant Mesothelioma Incidence in Eastern China,” also shows that the majority of cases are not linked to asbestos exposure, noting that other factors must be causing the disease in these patients.
In most regions in the world, more than 70 percent of mesothelioma cases are associated with asbestos exposure. But in China, only 15 percent of cases are linked to asbestos.
To confirm these findings, researchers at Zhejiang Cancer Hospital in China examined all mesothelioma cases diagnosed from 2002 to 2015 at two hospitals, located in areas characterized by different asbestos exposure: the Zhejiang Cancer Hospital (ZJCH) in Hangzhou, where there is no asbestos industry, and the Yuyao People’s Hospital in Yuyao, a Chinese textile asbestos industrial area. Patients were interviewed by a trained oncologist to assess asbestos exposure.
Among the 92 patients who were diagnosed with malignant mesothelioma (MM), the researchers used a large immunohistochemical panel to confirm the diagnosis in 52 patients, 28 from ZJCH and 24 from Yuyao.
A peculiar distribution of mesothelioma was found in these patients. In the United States, the male to female ratio is 4:1, but the researchers showed that this ratio was inverted in the study population, with women representing 75 percent of patients diagnosed with the disease.
The pleural to peritoneal MM ratio was also different in the Chinese patients compared to those seen in America: 1:5 compared to 1:3, and the median age at diagnosis was more than 20 years below the median age in the American population (50.6 years vs. 72 years).
Only 20 (one man and 19 women) of the 52 MMs were caused by asbestos exposure, accounting for 38 percent of the study population, suggesting that asbestos may not be the main cause of malignant melanoma in Chinese women.
“These findings point to a unique opportunity to investigate other causes of peritoneal MMs in this population, aside from asbestos,” the researchers wrote. And, given that an increasing number of peritoneal mesotheliomas in the United States and Europe also do not seem to be associated with asbestos, such studies may also benefit American and European populations.