In a recent study, a Yale Cancer Center team compared the performance of the four available PD-L1 assay tests.

They found that one of the assays failed to reveal comparable levels of PD-L1, a tumour-promoting protein, while three others revealed comparable levels.

The findings were presented September 26 at the International Association for the Study of Lung Cancer (IASLC) 2016 Chicago Multidisciplinary Symposium.

PD-L1 assays are used to test expression of the PD-L1 protein on a patient’s tumour to provide customised treatment options for drugs that may be more effective than chemotherapy in lung cancer.

The research team reviewed 90 surgically resected non-small cell lung cancer (NSCLC) cases (stages I-III) and sent a sample of each to four facilities for staining.

A group of 13 pathologists at 7 institutions then reviewed the samples, using 4 different assays on each case, and scored them using a unified scoring system. A comprehensive statistical analysis was then performed on the scores collected.

Currently, there are four drugs with four PD-L1 assays (22c3, 28-8, E1L3N, and SP142) available; but only the 22c3 test is required by the FDA for prescription of a targeted anti-PD-1 drug (pembrolizumab), while the others are not yet required for prescription of other PD-1 axis drugs.

Analysis revealed that one of the assays, SP142, systematically returned statistically lower levels of PD-L1 expression than the other three.

This was true in both tumour and immune cells using any test.

The remaining three assays available (28-8, E1L3N, and 22c3) showed no significant difference between them, according to researchers.

“Our data shows that the SP142 assay shows significantly lower levels of PD-L1 expression. This observation may limit the use of this assay in PD-L1 testing moving forward,” said David L. Rimm, MD, PhD, first author on the study and a Professor of Pathology and of Medicine (Medical Oncology), Yale School of Medicine. “However, the other three assays seem equivalent, which is good news for the future when other PD-1 axis drugs with assay-specific diagnostics gain FDA approval.”

Source: IASLC 2016