High PD-L1 Levels Could Be Bad News for Mesothelioma Surgery Candidates

Yet another new study has found a link between PD-L1 levels and mesothelioma survival – this time in people slated to have surgery for malignant pleural mesothelioma. 

PD-L1 stands for programmed cell death ligand 1. It is a protein expressed by some cancer cells that helps them avoid immune system attack. 

Researchers at Baylor College of Medicine are the latest to show that higher PD-L1 levels may lead to a worse mesothelioma prognosis. Their study focused specifically on mesothelioma surgery candidates. 

The results were published recently in the Annals of Thoracic Surgery. 

PD-L1 Levels and Mesothelioma Prognosis

Even healthy people express some amount of PD-L1. Its job is to suppress the part of the immune system that attacks foreign tissues. It helps to protect a growing fetus, for instance. 

But in the case of mesothelioma, elevated PD-L1 levels are not good. The protein can keep cancer-killing immune system cells from doing their job. If the immune system cannot kill mesothelioma cells in the early stages, asbestos cancer can spread even faster. 

Researchers have only recently made the connection between PD-L1 levels and mesothelioma prognosis. The Baylor study takes it a step further. It applies doctors’ growing understanding of PD-L1 to mesothelioma surgery.

Planning for Mesothelioma Surgery

Many studies suggest that, if a person is healthy enough, mesothelioma surgery may give them the best odds of survival. If surgeons can remove all or most of the mesothelioma tumor, chemotherapy and/or radiation might be able to kill the remaining cells. 

But mesothelioma surgery is also hard on the body and carries many risks. Until recently, PD-L1 levels have not played into surgical decision-making for mesothelioma. 

But the Baylor study could change that. Researchers started with a meta-analysis of 14 studies including more than 1600 patients to confirm that high PD-L1 levels are linked to poor mesothelioma survival. 

Then they analyzed PD-L1 expression in 75 patients who had surgery for pleural mesothelioma. Sixty-five percent of the patients had PD-L1 levels above one percent. Patients with non-epithelioid subtypes tended to have the highest levels. 

“High tumor PD-L1 expression was independently associated with poor overall survival,” writes lead author Hyun-Sung Lee. “The association of PD-L1 overexpression with unfavorable survival was more significant in epithelial MPMs than non-epithelial MPMs.” 

Dr. Lee says almost a third of patients with non-epithelioid mesothelioma had tumors with over 50 percent PD-L1 expression. 

The researchers validated their findings in two other groups of patients. They concluded that patients and doctors should consider PD-L1 levels when making decisions about surgery. 

“Tumor PD-L1 expression is a prognostic biomarker in patients undergoing surgical resection for malignant pleural mesothelioma and may be useful in perioperative decision making,” they write. 

Source:

Lee, HS, et al, “Prognostic Role of Programmed Cell Death 1 Ligand 1 (PD-L1) in Resectable Pleural Mesothelioma”, November 26, 2020, Annals of Thoracic Surgery, Online ahead of print, https://linkinghub.elsevier.com/retrieve/pii/S0003497520320075