Abstract 2254: Variations in the epithelial-mesenchymal transition (EMT) program by non-small cell lung cancer (NSCLC) circulating tumor cells (CTCs) do not influence survival

Abstract

Abstract Background By definition, CTCs must undergo the EMT to enter the bloodstream where they can be isolated from cancer patients for translational and biological study. Here we examined survival patterns in relation to CTC EMT expression in different molecular subgroups of NSCLC. Methods 125 patients (pts) with advanced treatment-naïve stage IIb-IV NSCLC were prospectively included for CellSearch CTC analysis as part of the Gustave-Roussy MSN study. Patients signed an informed consent for one CellSave tube prior to chemotherapy. Anti-vimentin (vim) antibody was added to the free channel in the CellSearch system for examination of EMT. Association of CTC number with clinical characteristics were assessed using Fisher's exact, Mann-Whitney and chi-squared tests. Kaplan-Meier method and log-rank tests were used to analyse progression-free survival (PFS) and overall survival (OS) of vimentin-expression in molecular subgroups of NSCLC. Results 51/125 pts (40.8%) were CTC-positive by CellSearch (≥2 CTC), and 29/125 (23.2%) patient samples contained at least 1 vimentin-positive (+) CTC. 19/76 (25%) adenocarcinomas were KRAS mutated. In the KRAS subgroup, 0/19 patient samples (0%) from pts with mutated KRAS contained vim+ CTC, compared to 17/48 pts (35.4%) with wild-type (WT) KRAS (p = 0.0027). There was also a significantly higher overall number of vim+ CTCs in pts with KRAS WT cancer compared to KRAS mutated cancer (mean 0 vs 1.63, respectively, p = 0.0035). For KRAS WT pts, no survival difference was evident between vim+ and vim- subgroups in terms of PFS or OS. 21/89 adenocarcinomas were EGFR mutated (23.6%). In this subgroup, statistically higher numbers of EGFR mutated pts with both vim+ and total CTCs were observed compared to EGFR WT pts (vim+ CTC: 9/21 EGFR mutated vs 9/56 EGFR WT, p = 0.0134; total CTC: 12/21 EGFR mutated vs 18/56 EGFR WT, p = 0.0451). Similarly, there was a significantly higher overall number of vim+ CTCs in pts with EGFR mutated cancer compared to pts with EGFR WT cancer (mean 1.24 vs 0.91, respectively, p = 0.0189), but no PFS or OS difference was evident between vim+ and vim- subgroups in EGFR mutated pts. 14/71 (19.7%) adenocarcinomas were ALK rearranged, with further results pending. Conclusions At baseline stage IIIb-IV disease, there are statistically fewer vim+ CTCs (and pts with vim+ CTCs) in KRAS mutated NSCLC, while vim+ CTC (and vim+ CTC pts) are statistically higher in EGFR mutated NSCLC. Despite this differential CTC vimentin expression between molecular subgroups, no PFS or OS difference is evident between vim+ and vim- patients. This biological variation coupled to a lack of overall clinical impact favours the hypothesis that each individual CTC is a highly plastic cell that can cover a range of EMT expression. Citation Format: Colin R. Lindsay, Vincent Faugeroux, Emma Pailler, Maria-Virginia Bluthgen, Chloé Pannet, Maud Ngo-Camus, Guillaume Bescher, Fanny Billiot, Jordi Remon, Philippe Vielh, David Planchard, Jean-Charles Soria, Benjamin Besse, Françoise Farace. Variations in the epithelial-mesenchymal transition (EMT) program by non-small cell lung cancer (NSCLC) circulating tumor cells (CTCs) do not influence survival. [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 2254.