PMC6135433_01
(A) Immunohistochemical staining (IHC) of programmed cell death ligand 1 (PD-L1) from biopsy specimens after treatment with osimertinib as the eighth-line treatment showed PD-L1 tumor proportion score (TPS)  90%. (B) IHC of PD-L1 from surgical specimens before chemotherapy and epidermal growth factor receptor tyrosine kinase inhibitors showed PD-L1 TPS 1%-24%.
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Immunohistochemistry using 22C3 PD-L1 antibody on the lung tumor tissue revealed a high expression level of PD-L1 (tumor proportion score (TPS) 90%) (Figure 1A). TPS of PD-L1 in surgically resected lung tumor tissue was 25% (Figure 1B). The PD-L1 expression level changed after administration of several EGFR-TKIs and chemotherapy.
Pembrolizumab followed by gemcitabine therapy showed antitumor effects.. Notes: Chest computed tomography scan images obtained before administration of pembrolizumab (A, B) and at 2 months after three cycles of pembrolizumab showing stable disease (C, D) and after 2 months of administration of gemcitabine showing a partial response (E, F). Arrowheads indicate pulmonary metastatic lesions.
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Three cycles of pembrolizumab produced stable disease (SD) (Figure 2A-D). After 2 months, gemcitabine produced a partial response (PR) (Figure 2E and F).