Circulating Tumor Cell-based Molecular Responses Stratify EGFR-TKI Efficacy in Patients with EGFR-Mutant Lung Cancer.

Background: Liquid biopsy offers a minimally invasive alternative to tissue biopsy, enabling therapeutic monitoring, precision medicine-based treatment decisions, and detection of tumor heterogeneity. Circulating tumor cell (CTC) analysis is a promising minimally invasive biomarker for monitoring treatment response and stratifying prognosis in EGFR-mutant non-small cell lung cancer (NSCLC). Meanwhile, detection of CTCs in peripheral blood is challenging due to their rarity and the limitations of both marker-dependent and marker-independent isolation techniques, which may compromise sensitivity and specificity. Continuous Centrifugal Microfluidics - Circulating Tumor Cell Disc (CCM-CTCD) enriches heterogeneous CTCs through automated microfluidic extraction and leukocyte depletion without interrupting centrifugation. Method: In this study, 77 EGFR-mutant NSCLC patients treated with EGFR-TKIs were enrolled. CTCs were isolated using CCM-CTCD before and after EGFR-TKI treatment and compared with plasma cfDNA and tissue biopsy for EGFR mutation analysis. CK-positive, CD45-negative CTCs were isolated and visualized using immunofluorescence staining. Patients were categorized as CTC molecular responders or non-responders based on a ≥30% reduction in CTC count from baseline. Progression-free survival (PFS) and tumor burden changes were evaluated. Results: The CCM-CTCD method showed concordance with Cobas® liquid biopsy but demonstrated superior sensitivity in detecting EGFR mutations. Mutational discordance between tissue, plasma cfDNA, and CTCs highlighted tumor heterogeneity. CTC molecular responders had significantly longer median PFS (46.3 vs. 12.2 months) and greater tumor burden reduction (-39.2% vs. -32.2%, p = 0.025) compared to non-responders. Multivariable analysis revealed that CTC molecular response was an independent predictor of improved PFS (HR 0.45, p = 0.023). Additionally, a non-significant trend was observed toward shorter PFS in patients receiving later-line treatments compared to first-line (HR 1.30, p = 0.523), first- or second-generation EGFR-TKIs compared to third-generation EGFR-TKIs (HR 1.59, p = 0.196), and in those with a history of smoking (HR 1.45, p = 0.300). CTC profiling was found to complement traditional methods for identifying genomic alterations and predicting early progression. Conclusion: CTC analysis using CCM-CTCD demonstrates potential as a reliable tool for predicting treatment response and stratifying prognosis in EGFR-mutant NSCLC. Stratifying patients based on CTC molecular response may guide treatment intensification strategies, offering a pathway for risk-adapted precision oncology. Prospective studies are warranted to validate these findings and optimize therapeutic decision-making. Citation Format: Seoyoung Lee, Chaeyeon Kim, Chang Gon Kim, Min Hee Hong, Mina Han, Wonrak Son,Gamin Kim, Minseok Kim, Hye Ryun Kim. Circulating tumor cell-based molecular responses stratify EGFR-TKI efficacy in EGFR-mutant lung cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1987.

Epithelial growth factor receptor (EGFR) mutations are present in 10%–26% of non-small cell lung cancer (NSCLC) tumors and are associated with the response to tyrosine kinase inhibitors (TKIs). This study aimed to detect and quantify the presence of circulating tumor cells (CTCs) in EGFR-mutant NSCLC patients and investigate their possible role in providing prognostic information. Enrolled patients received erlotinib (150 mg) or gefitinib (250 mg) orally once daily as the first-line treatment. Serial blood samples were taken at baseline (CTC-d0) and on day 28 (CTC-d28) following the initiation of erlotinib/gefitinib for detection of CTCs using the CellSearch system. CTCs ≥2 were found in 47/107 (44%) and CTCs ≥5 in 17/107 (15%). The CTC measurements were dichotomized as favorable (<5 CTCs) and unfavorable (≥5 CTCs) groups. The median progression-free survival (PFS) interval for patients in the favorable group at baseline was 11.1 months, significantly longer than the median PFS time of 6.8 months achieved by patients in the unfavorable group (p = 0.009). Patients in the favorable group on day 28 exhibited significantly longer PFS compared with patients in the unfavorable group (11.6 vs. 6.3 months; p < 0.0001). In univariate analysis, CTC-d0 ≥ 5 versus CTC-d0 = 0–4 was significantly associated with poor PFS and time-to-treatment failure (TTF). CTC-d28 ≥ 5 versus CTC-d28 = 0–4 was significantly associated with a poor PFS outcome. CTC-d0 and CTC-d28 remained independent poor prognostic markers in the stepwise multivariate analysis. Our study indicates that the CTC count is a prognostic factor for PFS and TTF outcomes in patients with advanced EGFR-mutant NSCLC.

P26.02 A Phase II Trial of Neoadjuvant Osimertinib for Surgically Resectable EGFR-Mutant Non-Small Cell Lung Cancer: Updated Results

e21149 Background: EGFR mutations are detected in 15-62% of patients with non-small cell (NSCLC) lung cancer. We can use tyrosine kinase inhibitors (such as erlotinib, gefitinib, afatinib) to treat patients with EGFR-mutant lung cancer. Tyrosine kinase inhibitors improve the survival outcomes of the patients. This study aimed to assess predictors of overall response rate (complete or partial response) in EGFR-mutant non-small cell lung cancer patients treated with EGFR inhibitors. Methods: Data of the EGFR-mutant lung cancer patients were evaluated retrospectively. Clinical, pathological, radiological, and treatment features of the patients were recorded. SPSS 25 version was used for statistical analysis. Kaplan-Meier and Cox-regression methods were used for survival analysis. Also, predictors of overall response were evaluated with logistic regression analysis. Results: 105 patients were included in the study. The female/male patients ratio was 1.25, and the median age was 61 (range, 33-85) years. Adenocarcinoma (90.4%) was the most common histopathological type. The ratios of Exon 19, exon 21, and other (rare or multiple) mutations were 59%, 25%, and 16%, respectively. 89 (84.9%) patients were de-novo metastatic at diagnosis. Before EGFR inhibitor therapy, the patients had received chemotherapy (22.9%) and palliative radiotherapy (40%). The patients received erlotinib (83.8%) or other EGFR inhibitors (16.2%) for treatment. Median overall survival was 30.8 (range 20.2-41.4) months. Overall response rate (complete or partial response) was 61.9%, stable response 11.4%, and progressive disease 26.7%. In logistic regression analysis, we found that age (p = 0.008), number of metastasis sites (p = 0.037), pathological type (adenocarcinoma or other types) (p = 0.001) were statistically significant for the overall response rate. However, gender (p = 0.98), tumor localizations (left or right lung) (p = 0.39), de-novo metastasis (p = 0.81), EGFR mutations type (p = 0.13), and type of EGFR inhibitör (p = 0.30) were not statistically significant. Conclusions: In this study, we showed real-life outcomes of the patients with EGFR-mutant metastatic non-small cell lung cancer. The data of predictors of overall response for EGFR inhibitors is limited. We detected that age, the number of metastatic organs, and histopathological type of tumor were affected the response of treatment.

The Promise of Circulating Tumor Cells in Metastatic CRPC

OA09.03 Pembrolizumab in Combination With Platinum-Based Chemotherapy in Recurrent EGFR/ALK-Positive Non-Small Cell Lung Cancer (NSCLC)

Purpose: Circulating tumor cells (CTCs) can be detected in the bloodstream of cancer patients in diverse epithelial cancers and elevated levels or increases in CTC counts portend poor prognosis. Less is known about the potential application of CTCs as surrogate endpoints, or as a source of cells for predictive biomarker evaluation in patients with advanced cancer enrolled in early phase clinical trials. This study investigated the feasibility of CTC enumeration, phenotypic characterization, as well as oncogenic mutation detection from CTCs and circulating tumor DNA (ctDNA) in patients with advanced lung cancer enrolled in a global multi-center, phase II clinical trial. Patients and Methods: Forty-one patients with advanced NSCLC who had received at least one prior chemotherapy regimen were enrolled in a phase 2, single-arm clinical study of the combination therapy with erlotinib and pertuzumab. Erlotinib is a small molecule inhibitor of epidermal growth factor receptor (EGFR), and pertuzumab is a monoclonal antibody that blocks HER2 dimerization with other HER family receptors. Peripheral blood was collected prior to the start of therapy and during the course of the study. Analyses in CTCs included enumeration, evaluation of EGFR expression and detection of oncogenic mutations in both CTCs and ctDNA and correlations were made to tumor response as measured by tumor FDG-PET changes or by computed tomography (CT) imaging. Results: CTC were detected (≥1 CTC) at baseline in 78% of patients (n=30). EGFR expression was evaluated in CTCs by immunofluorescence and revealed a range of expression levels and substantial heterogeneity for this biomarker in CTCs. Greater sensitivity for mutation detection was observed in ctDNA when compared to CTCs across a 6-gene panel (EGFR, KRAS, BRAF, NRAS, AKT1 and PIK3CA). Importantly, mutation detection in ctDNA was highly concordant with mutation status in patient tumor. Higher baseline CTC counts were observed in patients with EGFR mutations or with other oncogenic activating mutations, suggesting that CTC counts may be associated with underlying tumor genotype. A trend toward lower CTC counts was observed across on-treatment time-points, with statistically significant decreases in CTC counts (p=0.02) observed in either FDG-PET or RECIST responders. In comparison, no significant decreases were observed in non-responders. Conclusion: We demonstrate feasibility of enumeration and phenotypic characterization in CTCs and mutation detection in ctDNA from NSCLC patients in a global, multi-center Phase II study. In addition, our data provides the first evidence of a possible correlation between decreases in CTC counts and response by either FDG-PET or RECIST in patients with advanced NSCLC. These findings will require prospective validation but suggest a potential future role for using CTC decreases as an early indication of response to therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr PR-3.

Circulating Tumor Cell Assessment in Presumed Early Stage Non-Small Cell Lung Cancer Patients Treated with Stereotactic Body Radiation Therapy: A Prospective Pilot Study

MA08.07 Prospective Sequential Counts of Total CTC or cKIT+CTC in Advanced NSCLC with 1st Line Chemotherapy (POLICE)

11025 Background: Circulating tumor cell (CTC) detection and enumeration is a valuable tool for monitoring cancer patient status and outcome. While many current techniques employ immunomagnetic-enrichment based protocols focused on the importance of a particular CTC number as the indicator of patient status or outcome, we employ a cytometric, enrichment free approach using an immunofluorescent protocol to monitor CTC counts in patients with non-small cell lung cancer (NSCLC) over the course of treatment. Methods: Eligible patients had progressive stage IV NSCLC. The histological subtypes in the 42 cases for which the data was available included adenocarcinoma (22/42), squamous cell carcinoma (6/42), large cell undifferentiated carcinoma (3/42), and non-small cell lung carcinoma not further described, poorly differentiated, or with a mixed pattern (11/42). Blood samples were collected 3 wks, 3 mo, 6 mo, 9 mo, and 1 yr after the initial sample. CTCs were identified via immunofluorescence and cytometric analysis. Patient response to therapy was determined by RECIST every 3 months between time 0 and time 12 mo. Results: 80 of 109 patient samples have CTCs (73%) and all of the 52 patients tested have CTCs. 13 of 52 patients have CTC data for time 0 and 3 wks. Only 4 of these patients (30.8%) show a correlation linking CTC count change between time 0 and 3 wks and clinical assessment. 13 patients have CTC data for time 0 and 3 mo, 10 of whom show a correlation linking CTC count change between time 0 and 3 mo and clinical assessment. 7 of the 8 patients (87.5%) showing stable or partial response at 3 mo show a decrease in CTC count between time 0 and 3 mo. Five of the 6 patients (83.3%) clinically showing progressive disease at the 3 mo time point show an increase in CTC count between time 0 and 3 mo. The patients that do not show a correlation linking CTC count change between time 0 and 3 mo and clinical assessment at 3 mo show a correlation at the 6 mo time point. Conclusions: CTCs can be effectively enumerated in metastatic NSCLC patients, with the majority demonstrating CTCs in the setting of progressive disease. The change in CTC count at 3 mo, but not at 3 wks, correlates with radiographic response to chemotherapy. Further follow-up will determine the predictive value of CTC enumeration on survival. No significant financial relationships to disclose.

Combination of radiotherapy and PD-L1 blockade induces abscopal responses in EGFR-mutated lung cancer through activating CD8+ T cells

The present study aimed to assess the roles of peripheral circulating tumor cell (CTC) count, CTC subtypes and programmed death ligand 1 (PD-L1) expression in the clinical staging and prognosis of patients with non-small cell lung cancer (NSCLC). A total of 100 patients with NSCLC with available tumor tissues were enrolled in the present study, and 7.5 ml peripheral blood was collected. Patients were divided into PD-L1-positive and PD-L1-negative groups according to PD-L1 immunohistochemical staining. Peripheral blood samples from both groups were analyzed to determine the CTC count, epithelial-type CTCs (E-CTCs), mesenchymal-type CTCs (M-CTCs) and PD-L1 expression. Clinical data were collected, and patients were followed up for a maximum of 36 months, with patient death as the endpoint event. Patients with PD-L1-positive tumors had a worse prognosis compared with those with PD-L1-negative tumors (P=0.045). The PD-L1-positive group exhibited significantly higher numbers of CTCs and M-CTCs compared with the PD-L1-negative group (P≤0.05). However, the number of E-CTCs did not differ significantly between the two groups (P>0.05). PD-L1-positive patients with higher CTC and M-CTC counts had relatively poorer prognoses (P≤0.05), while the number of E-CTCs had no significant effect on prognosis (P>0.05). Compared with the early-stage NSCLC group, the late-stage NSCLC group exhibited a significant increase in the CTC count (P≤0.05), while E-CTC and M-CTC counts did not significantly differ between the two groups (P>0.05). The PD-L1-positive group exhibited a significant increase in the number of PD-L1+ CTCs and PD-L1+ M-CTCs compared with the PD-L1-negative group (P≤0.05), while PD-L1+ E-CTC counts did not differ significantly between the two groups (P>0.05). The PD-L1-positive patients with a higher number of PD-L1+ CTCs and PD-L1+ M-CTCs had relatively poorer prognoses (P≤0.05), while the PD-L1+ E-CTC count had no significant effect on prognosis (P>0.05). Compared with the early-stage NSCLC group, the late-stage NSCLC group exhibited a significant increase in the number of PD-L1+ CTCs and PD-L1+ M-CTCs (P≤0.05), while PD-L1+ E-CTC counts did not significantly differ between the two groups (P>0.05). Based on univariate and multivariate analyses, the number of PD-L1+ M-CTCs was identified as an independent prognostic factor for NSCLC. In conclusion, the presence of CTCs in peripheral blood, particularly PD-L1+ M-CTC subtype, indicated poorer clinical staging and prognosis in patients with NSCLC. These findings suggested that CTCs, specifically the PD-L1+ M-CTC subtype, could serve as a monitoring indicator for the clinical staging and prognosis of patients with NSCLC.

P3.01-008 Association between Icotinib Efficacy and Circulating Tumor Cell Levels in Advanced Non-Small Cell Lung Cancer

21O - EPAC-Lung: Pooled analysis of circulating tumor cells in advanced non-small cell lung cancer

11041 Background: Radiographic response remains the gold standard for assessment of the chemotherapy effect and has been used as a surrogate endpoint in clinical trials. Recently, circulating tumor cells (CTC) have emerged as a novel prognostic marker in many types of cancer; however, their significance has not been fully examined in patients with non-small-cell lung cancer (NSCLC). Methods: We conducted a prospective study to evaluate the clinical significance of CTC in metastatic NSCLC patients treated with chemotherapy. Peripheral blood samples were collected for CTC analysis before chemotherapy, after 1 cycle of chemotherapy, and after 2 cycles of chemotherapy. CTC analysis was performed using CellSearch (Veridex). Results: One hundred and forty-eight patients wereenrolledbetween August 2009 and January 2012, and 121 patients were eligible for the analysis. CTC was positive (CTC ≥1) in 30.6% (37/121) before chemotherapy, in 21.0% (26/118) after 1 cycle of chemotherapy, and in 21.6% (24/111) after 2 cycles of chemotherapy, respectively. CTC counts were higher in patients with N3 lymph node metastases (vs. N0-2, p = 0.0001), M1b status (vs. M1a, p = 0.0081) or ≥2 metastasis sites (vs. 1 metastasis site, p = 0.0342). Although not statistically significant, a positive trend was observed between the radiographic response and the dynamic change of CTC counts (p = 0.0734). In multivariate analysis, including the radiographic response (responder vs. non-responder), baseline CTC was a significant negative predictive factor for PFS (HR = 1.867; p = 0.0080) and OS (HR = 2.753; p = 0.0006). Considering pre- and post-treatment time points (before and after 2 cycles of chemotherapy) together, CTC-positive patients at either time point experienced significantly worse PFS (HR = 1.747; p = 0.0143) and OS (HR = 2.031; p = 0.0123) than those who were CTC negative at both time points. Conclusions: CTC was an independent prognostic factor in patients with metastatic NSCLC who was treated with chemotherapy.