21O - EPAC-Lung: Pooled analysis of circulating tumor cells in advanced non-small cell lung cancer

Abstract

Background: We assessed the clinical validity of circulating tumor cell (CTC) quantification for prognostication of patients with advanced non-small cell lung cancer (NSCLC) by undertaking a European pooled analysis of individual patient data. This is the largest study of its kind and the first to examine between-centre heterogeneity of CTC identification in NSCLC. Methods: Nine European NSCLC CTC centers were asked to provide reported/unreported anonymised data for patients with advanced NSCLC who participated in CellSearch CTC studies from January 2003 - March 2017. We used Cox regression models, stratified by centre, to establish the association between CTC count and survival. We assessed the added value of CTCs to prognostic clinico-pathological models using likelihood ratio (LR) statistics and c-indices. Results: Seven out of nine eligible centers provided data for 550 eligible patients, including 209 patients whose prognostic information was previously unpublished. CTC counts of ≥ 2 and ≥5 per 7·5 mL were associated with reduced progression-free survival (≥2 CTCs: HR 1.72, p < 0·001; ≥5 CTCs: HR 2.21, p < 0·001) and overall survival (≥2 CTCs: HR 2·18, p < 0·001; ≥5 CTCs: HR 2·75, p < 0·001), respectively. Survival prediction was significantly improved by addition of baseline CTC count to LR clinico-pathological models (log-transformed CTCs p < 0·0001; ≥2 CTCs p < 0·0001; ≥5 CTCs p < 0·0001), while more moderate improvements were observed with the use of c-index models. There was minor evidence of between-center heterogeneity in the effect on PFS, but not OS.No difference in CTC profile was observed between key NSCLC molecular subsets such as EGFR, ALK, and KRAS. Conclusions: These data confirm CTCs as an independent prognostic indicator of progression-free survival and overall survival in advanced NSCLC. CTC count improves prognostication when added to full clinico-pathological predictive models. ≥2 CTCs is an appropriate cutoff to move towards establishing clinical utility. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: C.R. Lindsay: Institutional funding for an ongoing phase II trial for which I am PI; Supported by Roche as part of an ESMO translational fellowship awarded in 2014-2016. F.H. Blackhall: Grants: AstraZeneca, Novartis, Pfizer, Amgen, BMS; Consultancy fees: Cell Medica, MSD; Speaker bureau: BI; Advisory board work: Regeneron, Medivation, AbbVie, Takeda, Roche, Ibsen. M.G. Krebs: Advisory board: J&J. L. Terstappen: Inventor on a number of US patents related to CellSearch, rights of which assigned to Johnson&Johnson, CellSearch kits obtained from Johnson&Johnson through a collaborative agreement with the MCBP. J-C. Soria: Consultancy fees: AZ, Astex, Clovis, GSK, GamaMabs, Lilly, MSD, Mission Therapeutics, Merus, Pfizer, PharmaMar, Pierre Fabre, Roche/Genentech, Sanofi, Servier, Symphogen, Takeda; Full time employee: MedImmune; Shareholder: AZ, Gritstone. All other authors have declared no conflicts of interest.