Circulating tumor cells (CTCs) hold great potential to answer key questions of how non-small cell lung cancer (NSCLC) evolves and develops resistance upon anti-PD-1/PD-L1 treatment. Currently, their clinical utility in NSCLC is compromised by a low detection rate with the established, Food and Drug Administration (FDA)-approved, EpCAM-based CellSearch((R)) System. We tested an epitope-independent method (Parsortix(TM) system) and utilized it to assess PD-L1 expression of CTCs from NSCLC patients. We prospectively collected 127 samples, 97 of which were analyzed with the epitope-independent system in comparison to the CellSearch system. CTCs were determined by immunocytochemistry as intact, nucleated, CD45(-), pankeratins (K)(+) cells. PD-L1 status of CTCs was evaluated from 89 samples. With the epitope-independent system, >/=1 CTC per blood sample was detected in 59 samples (61%) compared to 31 samples (32%) with the EpCAM-based system. Upon PD-L1 staining, 47% of patients harbored only PD-L1(+)CTCs, 47% had PD-L1(+) and PD-L1(-)CTCs, and only 7% displayed exclusively PD-L1(-)CTCs. The percentage of PD-L1(+)CTCs did not correlate with the percentage of PD-L1(+) in biopsies determined by immunohistochemistry (p = 0.179). Upon disease progression, all patients showed an increase in PD-L1(+)CTCs, while no change or a decrease in PD-L1(+)CTCs was observed in responding patients (n = 11; p = 0.001). Our data show a considerable heterogeneity in the PD-L1 status of CTCs from NSCLC patients. An increase of PD-L1(+)CTCs holds potential to predict resistance to PD-1/PD-L1 inhibitors.
- Janning, M.
- Kobus, F.
- Babayan, A.
- Wikman, H.
- Velthaus, J. L.
- Bergmann, S.
- Schatz, S.
- Falk, M.
- Berger, L. A.
- Bottcher, L. M.
- Pasler, S.
- Gorges, T. M.
- O'Flaherty, L.
- Hille, C.
- Joosse, S. A.
- Simon, R.
- Tiemann, M.
- Bokemeyer, C.
- Reck, M.
- Riethdorf, S.
- Pantel, K.
- Loges, S.
Keywords
- Nsclc
- PD-1/PD-L1 inhibition
- circulating tumor cells
- resistance
