Patients with the rarest mesothelioma subtypes tend to experience shorter mesothelioma survival. Now, new mesothelioma research suggests that may have something to do with a protein called PD-L1.
French researchers studied the PD-L1 levels in the tumors of 214 mesothelioma patients. They compared the levels with each patient’s subtype and their treatment outcome.
The results may help explain cases of shorter mesothelioma survival, especially among patients with sarcomatoid or biphasic mesothelioma subtypes.
PD-L1 Levels and Shorter Mesothelioma Survival
Programmed death ligand 1 (PD-L1) is one of the proteins that helps mesothelioma cells and other cancers “hide” from the immune system.
Normally, the immune system finds and destroys renegade cells. But if a patient’s mesothelioma tumor expresses higher amount of PD-L1, that tumor is more likely to go undetected.
This leads to worse treatment outcomes and shorter mesothelioma survival.
Subtype May Impact PD-L1
The new French study included 214 patients with malignant pleural mesothelioma. Eighty-four percent of patients had epithelioid mesothelioma, the most common subtype.
Thirty-six percent of the 214 patients tested positive for PD-L1. If more than 1% of their tumor cells expressed PD-L1, they tended to experience shorter mesothelioma survival. These patients lived for a median of 12.3 months while patients with fewer PD-L1-expressing cells had a median survival of 22 months.
“Sarcomatoid/biphasic subtypes were more commonly PD-L1 positive than epithelioid subtype,” writes lead author Solenn Brosseau in Clinical Lung Cancer.
For some patients, PD-L1 also appeared to impact how long it took for cancer to start growing again after treatment.
Epithelioid mesothelioma patients with a high number of PD-L1-expressing cells (over 50%) saw tumor growth again in just 6.7 months. If they had fewer PD-L1-expressing cells (less than 50%), it took a median of 9.9 months for their mesothelioma tumor to start growing again after treatment.
Combatting Shorter Mesothelioma Survival with New Drugs
The new research mirrors what other PD-L1 studies have shown. A 2017 Australian study also found a strong link between PD-L1 overexpression and shorter mesothelioma survival.
But the news may not be all bad for mesothelioma patients with higher PD-L1. Certain new mesothelioma drugs only work for patients whose tumors overexpress PD-L1.
These include the PD-L1 blockers pembrolizumab (Keytruda), nivolumab (Opdivo), and avelumab (Bavencio). These drugs help “unmask” mesothelioma tumors so that the immune system can help fight them.
Mesothelioma patients cannot alter their PD-L1 level. But there are still things they can do to raise the odds of surviving mesothelioma.
Twenty-year mesothelioma survivor Paul Kraus advocates plenty of fruits and vegetables, exercise, prayer, meditation, and supplements.
Brosseau, S, et al, “Shorter Survival in Malignant Pleural Mesothelioma Patients With High PD-L1 Expression Associated With Sarcomatoid or Biphasic Histology Subtype: A Series of 214 Cases From the Bio-MAPS Cohort”, May 13, 2019, Clinical Lung Cancer, Epub ahead of print, https://www.clinical-lung-cancer.com/article/S1525-7304(19)30101-9/fulltext
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