CT‐guided transthoracic needle biopsy for evaluation of PD‐L1 expression: Comparison of 22C3 and SP263 assays

BACKGROUND: Although there have been several studies on concordance of different assays testing programmed cell death ligand-1 (PD-L1) expression using surgical specimens, studies using real-world biopsy specimens are scarce. However, many of the non-small cell lung cancer (NSCLC) cases requiring immunotherapy and thus PD-L1 testing are unresectable having to rely on small biopsy results. Therefore, we sought to assess the concordance of two diagnostic assays (22C3 and SP263) in evaluating PD-L1 expression using specimens from CT-guided transthoracic needle biopsy (TNB) specimens in a routine clinical setting. METHODS: A total of 202 NSCLC cases that underwent CT-guided TNB from April 2017 to February 2018 were retrospectively reviewed. Biopsy specimens tested with both 22C3 and SP263 assays were included. Concordance of PD-L1 expression levels determined by two assays was assessed using intraclass correlation coefficient, and the agreement of dichotomized values at various cutoffs (1%, 25%, and 50%) were assessed using Cohen's κ coefficient of agreement. RESULTS: A total of 80 patients (M:F = 47:33, mean age: 68.0 years) were included in the study. Concordance of PD-L1 expression levels was high (intraclass coefficient: 0.892) between 22C3 and SP263 assays. Agreements at cutoff levels of 1%, 25%, and 50% were also good, with κ values of 0.878, 0.698, and 0.790, respectively. Positive percent agreement was 93.2%, 100.0%, and 95.2% for agreements at 1%, 25%, and 50%. CONCLUSION: There is a high concordance of PD-L1 expression evaluated with 22C3 and SP263 assays using CT-guided TNB specimens.