Cure Alveolar Soft Part Sarcoma International (iCureASPS)

Just came across this article when the biopsies were taken to find out the expression of programmed death ligand-1 (PD-L1) on tumor cells in lung cancer patients before the surgery and comparing to the same test done on a whole tumor tissue after it was resected.

Comparative study of the PD-L1 status between surgically resected specimens and matched biopsies of NSCLC patients reveal major discordances: a potential issue for anti-PD-L1 therapeutic strategies.
http://www.ncbi.nlm.nih.gov/pubmed/26483045

They found that PD-L1 expression was frequently discordant between surgical resected and matched biopsy specimens (the overall discordance rate = 48%; 95% confidence interval 4.64-13.24) and κ value was equal to 0.218 (poor agreement). In all cases, the biopsy specimens underestimated the PD-L1 status observed on the whole tissue sample. So overall the biopsy to find out this expression is useless (as of now) and can not be used as a rationale to start or not the PD-L1 treatment or clinical trial.

It seems like this study is indicating that there is a problem with false negatives, not false positives. Accordingly, a positive PD-L1 expression test is still useful. Unfortunately, with a biopsy, there is always a chance of missing the portion of the sample with the cells that you are looking for. However, it is clear that this means that a negative PD-L1 expression test should not be used to guide a patient away from immunotherapy.