The findings of a study presented at the International Association for the Study of Lung Cancer (IASLC) 2016 Chicago Multidisciplinary Symposium in Thoracic Oncology (26 September 2016, Chicago, IL, , USA) comparing the effectiveness of four available PD-L1 assay tests, highlighted that one of the assays failed to elucidate comparable levels of the tumor-promoting protein, compared with the other three that did.
A team of researchers from Yale Cancer Center (CN, USA) examined 90 surgically resected non-small-cell lung cancer cases of various stages (I–III), and sent a sample of each of these to four different facilities for staining. A total of 13 pathologists from seven institutions subsequently reviewed the samples, using the four different assays on each sample, using a unified scoring system to record the results. The scores collected were then statistically analyzed.
PD-L1 assays are carried out to quantify PD-L1 expression in a patient’s tumor as to develop personalized treatment options, which may potentially be more effective than chemotherapy in lung cancers.
There are currently four therapies with four associated PD-L1 assays available: 22c3, 28-8 E1L3N and SP142. However, 22c3 is the only test that is required by the US FDA prior to prescription of anti-PD-1 drug, pembrolizumab.
The analyses demonstrated that the SP142 assay systematically presented statistically lower PD-L1 expression levels than the other assays. This was true in both tumor and immune cells when any of the tests was used. According to researchers, the 28-8, E1L3N and 22c3 assays displayed no significant difference between them.
“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,” commented first author on the study, David L Rimm (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.”