Cancer treatment and research communications | 2021
Discordance in PD-L1 scores on repeat testing of non-small cell lung carcinomas.
Abstract
INTRODUCTION\nPD-L1 expression may be used as a biomarker predictive of non-small cell lung carcinoma (NSCLC) response to PD-L1 inhibitor treatment. Spatial and temporal heterogeneity in PD-L1 expression and variation in PD-L1 test interpretation may contribute to differences in PD-L1 test results between samples of the same patient s disease.\n\n\nMETHODS\nRetrospective chart review identified 77 NSCLC patients with 22C3 PharmDx PD-L1 assays performed on two different tumor samples. Patients clinically suspected to have two separate primaries were excluded. PD-L1 test results in different score categories (<1%, 1-49% and ≥50%) were considered discordant. Clinical and pathologic factors associated with discordance were assessed.\n\n\nRESULTS\n28 (36%) of the 77 cases had discordant PD-L1 scores between samples. Patients with an initial test result of 1-49% were most likely to have a discordant second test result. Specimen type (cytology, small biopsy or resection), specimen site (lung, lymph node, pleura/pleural effusion or distant metastasis), time between specimen collection, and treatment between specimen collection were not significantly associated with the rate of discordance.\n\n\nCONCLUSIONS\nRepeat PD-L1 testing of the same patient s NSCLC results frequently resulted in discordant test results, independent of whether the samples differed in clinical or pathologic factors. This discordance rate underscores the extent to which PD-L1 levels are heterogeneous and difficult to accurately represent with a single test value. Further study of the predictive value of PD-L1 scores in cases with discordant results is needed.