PD-L1 Expression in Circulating Tumor Cells as a Promising Prognostic Biomarker in Advanced Non-small-cell Lung Cancer Treated with Immune Checkpoint Inhibitors.
Clin Lung Cancer 2021;
22:423-431. [PMID:
33849808 DOI:
10.1016/j.cllc.2021.03.005]
[Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/23/2021] [Accepted: 03/04/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND
Circulating tumor cells (CTCs) are a promising source of biological information in cancer. Data correlating PD-L1 expression in CTCs with patients' response to immune checkpoint inhibitors (ICIs) in non-small-cell lung cancer (NSCLC) are still lacking.
METHODS
This is a prospective single-center cohort study enrolling patients with advanced NSCLC. CTCs were identified and counted with the CellSearch system. PD-L1 expression on CTCs was assessed with phycoerythrin-conjugated anti-human PD-L1 antibody, clone MIH3 (BioLegend, USA). Primary endpoint was the correlation between the CTCs PD-L1 expression and overall survival (OS). Among secondary objectives, we evaluated the correlation between PD-L1 expression on CTCs and matched tumor tissue and the correlation of CTC number and baseline tumor size (BTS).
RESULTS
Thirty-nine patients treated with anti-PD-1/PD-L1 agents as second- or third-line therapy were enrolled. Patients were divided into 3 groups: no CTC detectable (CTCnull, n = 15), PD-L1 positive CTC (CTCpos, n = 13), and PD-L1 negative CTC (CTCneg, n = 11). Median OS in patients with CTCneg was 2.2 months, 95% confidence interval (CI), 0.8-3.6 (reference) versus 3.7 months, 95% CI, 0.1-7.5 (hazard ratio [HR] 0.33; 95% CI, 0.13-0.83; P = .019) in patients with CTCpos versus 16.0 months, 95% CI, 2.2-29.8 (HR 0.17; 95% CI, 0.06-0.45; P< .001) in patients with CTCnull. No correlation was found between PD-L1 expression on CTCs and on tumor tissue. CTC number was correlated with BTS.
CONCLUSION
PD-L1 expression on CTCs is a promising biomarker in patients with NSCLC treated with ICIs. Further validation as predictive biomarker is needed.
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