Abstract 2252: Correlation of baseline value of folate receptor-positive circulating tumor cells and efficacy of pemetrexed and dynamic monitoring study in non-small cell lung cancer patients receiving first-line platinum-based chemotherapy
Authors: Chen Xiaoxia , Zhou Caicun , Li Xuefei 
Published: July 2016

Abstract
Background: The efficacy of pemetrexed associates with the expression of folate enzymes, however, few serological marker is available to predict its efficacy. Moreover, dynamic monitoring of circulating tumor cell (CTC) count can predict the outcome of tumor therapy, the progress of tumor and the overall survival of the patient. By quantitative determination of folate receptor-positive CTCs, this study investigated the correlation of its baseline values to the efficacy of pemetrexed and performed a dynamic monitoring study in non-small cell lung cancer (NSCLC) patients who underwent first-line platinum-based chemotherapy.
Methods: This study enrolled 70 NSCLC patients who received first-line platinum-based chemotherapy. The CTCs were quantified by negative enrichment using immunomagnetic beads in combination with folate receptor-directed polymerase chain reaction(PCR) that allows secondary amplification of tiny amounts of CTCs in peripheral blood, thereby enhancing the sensitivity of detection. In this study, the CTC levels were examined by collecting 3mL of anti-ENTA whole blood samples before the treatment and after every chemotherapy, and followed up until progressive disease (PD) or completion of first-line chemotherapy. Based on the changes in CTC levels, we evaluated the correlation of the changes in CTC levels and the progress of the disease as well as the correlation of the CTC levels and the therapeutic outcomes.
Results: The CTC level of seventy patients was 13.68 CU/3mL. Of twenty-two patients who received pemetrexed disodium/platinum combined therapy (AP/AC), the patients harboring high levels of folate receptor showed greater efficacy than those with low expression levels (8.7&lt;CTC level&lt;16, n = 7; PFS: 448 vs.94days, P = 0.0199; ORR: 75% vs.11%). In the dynamic monitoring study, the CTC level (AUC = 0.8026,P = 0.0033), the CTC ratio (AUC = 0.8422,P = 0.0003), the rate of CTC changes (OR = 102.005,P = 0.0012) after the second chemotherapy and the CTC level (AUC = 0.9487,P&lt;0.0001), the CTC ratio (AUC = 0.8889,P&lt;0.0001), the changing rate of CTCs (OR = 51.662,P = 0.0031) after the fourth chemotherapy positively correlated to the disease progression.
Conclusions: The patients with high expression of folate receptor-positive CTCs appear to have superior response to pemetrexed than those with low expression. Additionally, the changes of CTC count can be used as a dynamic monitoring indicator in the treatment process to evaluate tumor burden and therapeutic outcomes.
Citation Format: Xiaoxia Chen, Caicun Zhou, Xuefei Li. Correlation of baseline value of folate receptor-positive circulating tumor cells and efficacy of pemetrexed and dynamic monitoring study in non-small cell lung cancer patients receiving first-line platinum-based chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2252.