Mesothelioma patients who express too much of the protein PD-L1 are less likely to survive the asbestos cancer than those whose cells express less.
That is the message from a new Australian study on mesothelioma prognosis, which backs up the findings from a number of previous PD-L1 studies.
In a report published in the Asia-Pacific Journal of Clinical Oncology, oncologist Bella Hai Nguyen and colleagues at The Canberra Hospital in Garran analyzed the clinical data on 58 malignant pleural mesothelioma patients treated there between 2006 and 2016.
As with previous studies on PD-L1, the Australian study found a link between overexpression of the protein and poor mesothelioma survival. Unlike other studies, though, the new study finds that an even higher percentage of mesothelioma patients than previously thought may exhibit this overexpression.
PD-L1 Expression in Mesothelioma Cells
Programmed death ligand 1 (PD-L1) is one of the proteins believed to help mesothelioma cells and other cancers avoid detection by the immune system, whose job it is to find a destroy renegade cells.
If a mesothelioma patient’s tumor expresses higher amounts of PD-L1, that tumor is more likely to be able to grow unchecked, leading to poorer treatment outcomes and worse survival odds.
Drugs designed to block PD-L1, like pembrolizumab (Keytruda), nivolumab (Opdivo), and avelumab (Avastin) have made the news in the past two years for their ability to “unmask” pleural mesothelioma tumors and make them more susceptible to treatment.
PD-L1 and Mesothelioma Survival
The mesothelioma patients included in the PD-L1 study were reasonably representative of mesothelioma patients around the world; most were male (84%) and most (72%) had the epithelioid subtype of mesothelioma.
Just under half of the patients examined for the study (47%) received chemotherapy alone or as part of a combination treatment.
When it came to PD-L1 expression, the team found that 42 of the mesothelioma patients (72.4%) overexpressed the protein. These patients had significantly shorter survival than those with normal PD-L1 levels.
“The median survival time for PD-L1 negative group is 15.5 months and 6 months for the positive group,” writes Dr. Nguyen. “Positive PD-L1 expression is independently correlated with worse prognosis.”
The new analysis found a higher percentage of malignant pleural mesothelioma patients with positive PD-L1 compared to other studies.
Although mesothelioma patients cannot alter their PD-L1 level, there are still a number of actions they can take to maximize their odds of surviving mesothelioma, including eating a diet rich in fruits and vegetables, minimizing stress through activities like exercise, prayer, and meditation, and considering complementary mesothelioma therapies.
Nguyen, BH, “PD-L1 expression associated with worse survival outcome in malignant pleural mesothelioma”, November 3, 2017, Asia Pacific Journal of Clinical Oncology, Epub ahead of print