P1.07-031 Clinical Evaluation of Folate Receptor-Positive Circulating Tumor Cells Detection in Patients with Small Cell Lung Cancer

Abstract

Small cell lung cancer (SCLC) is distinguished by extremely high numbers of circulating tumor cells (CTCs) in comparison to other malignancies; however, the role of CTCs in evaluating chemotherapy effect of SCLC is to be further clarified. The purpose of this study was to investigate the predictive and prognostic role of folate receptor–positive CTCs in unresectable SCLC. In this single-center prospective study, blood samples for folate receptor–positive CTCs analysis were obtained from 80 patients with chemotherapy-naive unresectable SCLC at baseline, after two cycles of chemotherapy, and on disease progression. All patients received chemotherapy with EC or EP regimen for at least two cycles. CTCs number at baseline, after chemotherapy and changes with chemotherapy were evaluated as predictive factors for chemotherapy effect, along with clinical characteristics. Of all 80 patients, CTCs was detected at baseline as positive (CTCs>8.7 FU/3mL) in 67 patients, with the percentage of 83.8%, which was not associated with age, sex, smoking status or disease stage. In 72 evaluable patients, the disease control rate was 83.9% (52/62) and 50% (5/10) in CTCs positive and negative patients respectively (P=0.004). In CTCs positive patients, those harboring low levels of folate receptor (8.7<CTCs<14, n=29) were associated with longer PFS (275 days, 95%CI:82-468) than those with high expression levels (CTCs ≥14, n=38)(PFS: 210days, 95% CI:159-261; P=0.0458). Reduction in CTCs number after two cycles of chemotherapy was associated with partial response (P=0.049) but not with stable disease (P=0.47). The results of a multivariate analysis showed that the baseline CTCs level was an independent prognostic factor for survival time (HR=2.19; P=0.024). CTCs number at baseline could be used as a useful prognostic biomarker for SCLC. Reduction in CTCs number with chemotherapy could predict better chemotherapy effect of SCLC.