156P: Correlation of baseline value of folate receptor-positive circulating tumor cells and efficacy of pemetrexed and dynamic monitoring study in NSCLC patients receiving first-line platinum-based chemotherapy

Dynamic Monitoring and Predictive Value of Circulating Tumor Cells in EGFR-Mutated Advanced Non-Small-Cell Lung Cancer Patients Treated With First-Line EGFR Tyrosine Kinase Inhibitors

BACKGROUND

There is an urgent need to develop a convenient and less invasive technique to monitor the efficacy of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) in patients with EGFR-mutated non-small-cell lung cancer (NSCLC). We proposed folate receptor-based assay to count circulating tumor cells (CTCs) to predict and dynamically monitor the therapeutic response to first-line EGFR-TKIs in patients with EGFR-mutated NSCLC.

PATIENTS AND METHODS

Eligible patients were enrolled, and 3 mL of blood was obtained before initial treatment, 1 month after treatment, and every 2 months thereafter. CTCs were isolated on the basis of negative enrichment by immunomagnetic beads and detected by a ligand-targeted PCR method.

RESULTS

A total of 232 patients with EGFR-mutated NSCLC and treated with first-line EGFR-TKIs were included. Patients with low baseline CTC count had a markedly longer progression-free survival (hazard ratio = 0.48; P < .001) and overall survival (hazard ratio = 0.52; P = .002) than those with high count. This difference remained significant in multivariate analysis. Dynamic change of CTC count was significantly associated with partial response (P = .042) and stable disease/progressive disease (P = .032). Notably, dynamic monitoring of CTC provided evidence of resistance to EGFR-TKIs before computed tomographic scanning with a median lead time of 113 days (range, 45-169 days).

CONCLUSION

The current evidence suggests that folate receptor-positive CTC counts can be used for both the dynamic monitoring and prediction of outcome in EGFR-mutated NSCLC patients treated with EGFR-TKIs, which could serve as an alternative or supplement to computed tomographic scanning.

Combined use of EpCAM and FRα enables the high-efficiency capture of circulating tumor cells in non-small cell lung cancer

Circulating tumor cells (CTCs) provide a new approach for auxiliary diagnosis, therapeutic effect evaluation, and prognosis prediction for cancer patients. The epithelial cell adhesion molecule (EpCAM)-based separation method (CellSearch) showed good clinical use in multiple types of cancer. Nevertheless, some non-small cell lung cancer (NSCLC) tumor cells have a lower expression of EpCAM and are less frequently detected by CellSearch. Here, we present a highly sensitive immunomagnetic separation method to capture CTCs based on two cell surface markers for NSCLC, EpCAM and Folate receptor alpha (FRα). Our method has been demonstrated to be more efficient in capturing NSCLC cells (P < 0.01) by enriching three types of CTCs: EpCAM⁺/FRα^-/low, EpCAM^-/low/FRα⁺, and EPCAM⁺/FRα⁺. In 41 NSCLC patients, a significantly higher CTC capture rate (48.78% vs. 73.17%) was obtained, and by using a cutoff value of 0 CTC per 2 ml of blood, the sensitivities were 53.66% and 75.61% and the specificities were 100% and 90% for anti-EpCAM-MNs or a combination of anti-EpCAM-MNs and anti-FRα-MNs, respectively. Compared with the tumor-specific LT-PCR based on FRα, our method can isolate intact FRα⁺ CTCs, and it is advantageous for additional CTC-related downstream analysis. Our results provide a new method to increase the CTC capture efficiency of NSCLC.