That conclusion comes from a group of researchers at Australia’s University of New South Wales. The researchers tested tissue samples from 42 mesothelioma patients for the presence of Ki67, a protein associated with cell proliferation. According to the authors, Ki67 has been widely used as a prognostic indicator in other types of cancer, but has not been tested in mesothelioma.
The researchers divided the tissue samples into two groups based on their level of Ki67 expression. Those with a Ki67 expression of less than 25% were put in the low category and all samples above that were classified as high. The tissue samples were further divided into the different peritoneal mesothelioma subtypes: epithelioid, sarcomatoid, and biphasic.
“High expression of Ki67 (≥25% by immunohistochemical evaluation) was correlated with poor survival in the overall group,” reports corresponding author and molecular biologist Krishna Pillai in the American Journal of Clinical Oncology. This held true in both male and female mesothelioma patients with the epithelioid subtypes. Independent of Ki67 expression, having the sarcomatoid type of mesothelioma, having a high peritoneal cancer index (a measure of the extent of peritoneal cancer) and being older than 60 were all associated with lower odds of mesothelioma survival.
The authors conclude that Ki67 expression “affects prognosis in malignant mesothelioma peritoneal mesothelioma patients and helps to predict survival within the various clinicopathologic categories.”
Peritoneal mesothelioma is a rare form one of the rarest types of cancers. Accounting for about a fifth of the annual cases of mesothelioma in the US, peritoneal mesothelioma starts on the membrane called the peritoneum that surrounds abdominal organs. Like all types of mesothelioma, it is associated with exposure to asbestos, often in a work setting. Patients who have been exposed to asbestos should be alert for early symptoms such as abdominal pain or swelling, diarrhea or constipation.
The pleural form of mesothelioma, which starts on the membranes surrounding the lungs, may first manifest itself as a cough, chest pain and/or shortness of breath.
Pillai, K et al, “Prognostic significance of Ki67 expression in malignant peritoneal mesothelioma”, August 2015, American Journal of Clinical Oncology, pp. 388-394