Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are powerful molecular targeted therapeutic agents for lung cancer. We recently developed an original immunocytology and glass slide-based circulating tumor cell (CTC) detection platform for both CTC enumeration and EGFR mutation analysis with DNA extracted from CTCs. Methods: Using this platform, we conducted a pilot clinical study for CTC enumeration in peripheral blood (PB), pulmonary arterial blood (PA), and pulmonary venous blood (PV) from 33 patients with lung cancer (Stage I–III) who underwent surgery, followed by digital PCR-based EGFR mutation analysis of CTCs in PV from 12 patients. Results: The results showed that CTC levels were significantly higher in PV and PA than in PB (p < 0.05, p < 0.01. respectively), with a notably greater number of small and large CTC clusters (p < 0.01). Genetic analysis of EGFR mutations of CTCs from PV (n = 12) revealed six mutations, including three Exon19del and three L856R, in CTCs and eight EGFR mutations, including five Exon19del and three L856R, in lung tumor tissue. CTC mutation status matched that of tissue samples in nine patients, was unmatched in two patients, and controversial in one patient, indicating a sensitivity of 0.75 (6/8) and specificity of 1.0 (4/4) with some false-negative results for the mutation analysis of CTCs. Conclusions: This immunocytology-based CTC detection platform is a convenient method for detecting both CTC number and EGFR mutation status under microscopy, suggesting its potential as a liquid biopsy tool in the hospital for patients with lung cancer in some clinical settings.

Background: Circulating tumor cells (CTCs) have recently been developed as biomarkers. Several studies have reported on the clinical use of CTCs to assess drug resistance in various cancers. However, sequential and multiple CTC measurements during chemotherapy are relatively rare. We recently reported a transient increase in CTCs early after chemotherapy by sequentially detecting CTCs in a human pancreatic cancer xenograft model in nude mice. Method: In the present study, using a newly developed immunocytology and glass slide-based convenient CTC detection platform, we examined CTC numbers sequentially before, during, and after chemotherapy in the peripheral blood of 14 pancreatic cancer patients, pathological stage (pStage) I-IV, who underwent surgery with preoperative chemotherapy and GS (Gem/S-1) and GnP (Gem/nab-PTX). Results: Among patients with strongly or weakly elevated CTC counts (3–44/5 mL of blood) following GS treatment, four out of six pancreatic cancer patients were judged to have a partial response (PR), and two out of six were deemed to have stable disease (SD) as a clinical response based on the CT image. In contrast, in patients with GnP therapy, three out of four patients showed no CTC response, and these three patients were judged to have progressive disease (PD), while the remaining one patient was judged to have SD in terms of their clinical response. Conclusion: These results suggest that sequential CTC monitoring during preoperative chemotherapy in pancreatic cancer patients can be a helpful liquid biopsy diagnostic tool as a therapeutic marker to predict tumor chemosensitivity and chemoresistance in clinical settings. Further large-scale clinical studies are required to confirm and clarify this hypothesis.