Author of

• 17398

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  P2.01 - Poster Session with Presenters Present (ID 461)

  • Event: WCLC 2016
  • Type: Poster Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 12/06/2016, 14:30 - 15:45, Hall B (Poster Area)

  • 17458

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    P2.01-060 - Comparative Analysis of PD-L1 Expression between Circulating Tumor Cells and Tumor Tissues in Patients with Lung Cancer (ID 5402)

    14:30 - 14:30  |  Author(s): K. Kanai
    • Abstract

    Background:
    Blockade of programmed death receptor-1 (PD-1) pathway has been shown to be effective against solid tumors including lung cancer. Although PD-ligand 1 (PD-L1) expression on tumor tissue is expected as a potential predictive biomarker, its detection remains challenging due to its dynamic and unstable status. Here, we evaluated the PD-L1 expression on circulating tumor cells (CTCs) in patients with lung cancer and investigated its concordance with that on tumor tissues.
    
    Methods:
    CTCs were captured and immune-stained using microcavity array system. CTCs were defined as those positive for DAPI and cytokeratin (CK) and negative for CD45. PD-L1 expression on CTCs was evaluated by addition of the process of PD-L1 immunocytochemistry. For CTCs detection, 3 ml of peripheral whole blood was collected from the patients who consented in written form and PD-L1 immunohistochemistry was performed using corresponding tumor tissues.
    
    Results:
    Sixty-seven lung cancer patients were enrolled in the study between July 2015 and April 2016 at Wakayama Medical University. Patient characteristics were as follows: median age 71 (range, 39 to 86); male 72%; stage II-III/IV, 15/85%; non-small cell lung cancer (NSCLC)/small cell lung cancer (SCLC)/Other, 73/21/6%. CTCs were detected in 66 out of 67 patients (median 19; range, 0 to 115) and more than 5 CTCs were detected in 78% of patients. PD-L1 expressing CTCs were detected in 73% of patients and the proportion score (PS) of PD-L1 expressing CTCs ranged from 3% to 100%, suggesting intra-patient heterogeneity of PD-L1 expression on CTCs. Significantly more PD-L1 expressing CTCs were detected in patients without EGFR mutations than those with EGFR mutations (P = 0.0385). Tumor tissues were available from 27 patients and were immune-stained for PD-L1. No positive correlation was observed on PD-L1 expression between tumor tissues and CTCs based on PS (R[2 ]= 0.0103). Three adenocarcinoma cases with PD-L1-positive tumor tissue did not harbor any PD-L1 expressing CTCs and conversely, three adenocarcinoma cases with PD-L1-negative tumor tissue harbored PD-L1 expressing CTCs, showing the total discrepancy between tumor tissues and CTCs. It is also noteworthy that SCLC patients had perfect agreement on PD-L1 expression between tumor tissues and CTCs.
    
    Conclusion:
    PD-L1 expression was detectable on CTCs in lung cancer patients and intra-patient heterogeneity of its expression was observed. There was no agreement between tumor tissues and CTCs on PD-L1 expression though it may differ among tumor histologies. Further investigation is warranted to better understand the clinical significance of PD-L1 expressing CTCs.