By Will Boggs MD
NEW YORK (Reuters Health) - 5/7/2019
The expression of programmed death ligand 1 (PD-L1) is common in locally advanced or metastatic non-small-cell lung cancer (NSCLC), according to a retrospective study across 18 countries.
"The results prove high consistency across geographic regions and suggest high overall reproducibility of immunohistochemistry (IHC)-based PD-L1 analysis when performed by experienced, trained pathologists," Dr. Manfred Dietel from Charite Universitaetsmedizin Berlin, in Germany, told Reuters Health by email. "This means IHC-based analyses of PD-L1 are a reliable basis to give immune-oncological drugs (check-point inhibitors) to patients."
Tumor expression of PD-L1 has been used to identify patients with NSCLC who are most likely to benefit from treatment with the highly selective monoclonal antibody pembrolizumab.
The prevalence of PD-L1 expression has largely been evaluated in clinical-trial populations, and little is known about global, real-world prevalence of PD-L1 expression in tumor cells of patients with advanced or metastatic NSCLC.
For the EXPRESS study, online June 12 in Lung Cancer, Dr. Dietel and colleagues examined tumor-sample data on 2,368 patients with stage IIIB/IV NSCLC. They assessed the prevalence of PD-L1 as the percentage of viable tumor cells showing partial or complete membrane staining (tumor proportion score, or TPS).
Overall, 48% of samples had PD-L1 TPS <1%, 52% had PD-L1 TPS of at least 1%, and 22% had PD-L1 TPS of at least 50%. The prevalence was similar across regions.
Tumor samples with PD-L1 TPS of at least 50% were less common among patients with sensitizing EGFR mutations and those with ALK translocations. No other demographic or clinical characteristics appeared to be associated with differences in the prevalence of PD-L1 expression.
"Overall," the researchers conclude, "these results indicate that 52% of patients with advanced NSCLC express PD-L1 on tumor cells (evaluated on histological material) and are potentially eligible for pembrolizumab monotherapy as first-line or second-or-later-line therapy."
"Physicians should cooperate only with pathologists who are trained and experienced in PD-L1-IHC," Dr. Dietel said. "Training with certificates should be documented by the pathologist responsible for PD-L1 reading."
Lung Cancer 2019.