1562PFolate receptor-positive circulating tumour cells as a predictive biomarker for the efficacy of first-line pemetrexed-based therapy in patients with non-squamous non-small cell lung cancer

Abstract Background There is a lack of well-established biomarkers to predict the efficacy of pemetrexed-based therapy. In this prospective phase II study, we investigated the correlation of folate receptor (FR)-positive circulating tumor cell (CTC) level with pemetrexed efficacy in patients with advanced non-squamous non-small cell lung cancer (nsNSCLC). Methods A total of 98 nsNSCLC patients were enrolled. Peripheral blood was collected from each patient prior to initiation of treatment. FR-positive CTCs were enriched by immunomagnetic leukocyte depletion and quantified using LT-PCR method. Results Patients with relatively low CTC level (11-16 FU/3 mL, n = 32) showed a significantly shorter progression-free survival (PFS) and overall survival (OS) compared to the ‘high CTC level group’ (≥16 FU/3 mL, n = 28; median PFS: 133 versus 320 days, hazard ratio[HR]=4.78, P = 0.0008; median OS: 632 days versus ‘not reached’, HR = 10.89, P = 0.0013). The ‘high CTC level group’ also achieved superior objective response rate (ORR) and disease control rate (DCR) over the ‘low CTC level group’ (ORR: 40.9% versus 9.5%, P = 0.0339; DCR: 100% versus 81.0%, P = 0.0485). The efficacy of pemetrexed in the ‘negative-CTC group’ ( Conclusions Our results implied that FR-positive CTC is an efficacious biomarker to predict the outcome of first-line pemetrexed-based therapy in nsNSCLC patients. Clinical trial identification ChiCTR-ONC-13003475. Legal entity responsible for the study Shanghai Pulmonary Hospital. Funding This study was partially supported by Shanghai Committee of Science and technology (No. 14411970800). The funder had no role in study design, data collection, data analysis, data interpretation, or writing of the report. Disclosure All authors have declared no conflicts of interest.