The results of an international study indicate that the expression of the nuclear protein Ki67 in the tumors of pleural mesothelioma patients can not only gauge the aggressiveness of the cancer but also help doctors choose the best treatment options. 

The study, published in the journal Cancers, compared the longevity of patients with high Ki67 expression to those with low Ki67 expression. Researchers found the 5-year survival rate for patients with less than 15% expression was more than four times higher than for those with more than 15% expression. Those in the lower expression group also responded better to surgery.  

“Ki67 is a protein of the cell nucleus that is specifically expressed, i.e., produced, during cell division,” wrote study leader Dr. Bahil Ghanim from the Division of General and Thoracic Surgery at Krems University Hospital in Austria. “The expression rate of the Ki67 genes is a suitable measurement. This indicates the proportion of cells in a tissue that are currently dividing and therefore producing Ki67.” 

Through an earlier study, the research team showed Ki67’s prognostic value—especially in epitheliod pleural mesothelioma, where mesothelioma cells grow faster and do not spread as easily as in more aggressive forms of the disease. 

In the more recent study, the team looked at whether Ki67 can predict the success of various types of therapy. The researchers found that patients with low Ki67 expression who received multiple types of treatment that included surgery had an average survival rate of four years—twice as long as high Ki67 expression patients who received the same treatment. 

“Ki67 is therefore also very well suited as a predictive biomarker that can provide information on the suitability of a specific form of treatment, including thoracic surgery,” stated Dr. Stephanie Iser,  the first author of the study, together with Dr. Sarah Hintermaier. “This means that Ki67 makes it possible for the first time to individualize the treatment of epithelioid pleural mesothelioma.”

The study was conducted by Karl Landsteiner University of Health Sciences (KL Krems) in collaboration with Gazi University, Ankara, Turkey.

What Is Pleural Mesothelioma?

Pleural mesothelioma accounts for more than three-quarters of all mesothelioma cases. It gets its name from the pleura, the membrane surrounding the lungs, where this form of cancer develops. 

Only 10% of those with malignant pleural mesothelioma survive for five more years once the disease develops. Patients who only have localized tumors are more likely to achieve a 5-year survival rate, while those whose tumors have spread beyond the lungs tend to die sooner. 

The average life expectancy for malignant pleural mesothelioma patients is 12 to 21 months. If patients are younger and the disease is diagnosed early on, they may survive longer, especially with treatment. 

The Link Between Asbestos and Mesothelioma 

Most mesothelioma cases result from asbestos exposure. From the mid-to-late 1900s, asbestos was frequently used in building construction materials because it can withstand heat and fire. 

Construction workers, plumbers, firefighters, shipyard workers, factory workers, insulation manufacturers, and installers are among those most likely to be exposed to asbestos. 

Asbestos use declined sharply once researchers discovered its link to various forms of cancer, including mesothelioma. In March 2024, the Environmental Protection Agency finally banned chrysolite, the last known type of asbestos used in the United States. 

However, unions and the nonprofit Asbestos Disease Awareness Organization have argued that the ban doesn’t go far enough. They say the EPA isn’t providing interim protections for all workers exposed to chrysolite during the phase-out period and that the ban doesn’t address risks of exposure to other types of legacy asbestos, such as tremolite and anthophyllite. Those two varieties have been found in talcum powder consumer products.