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.
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.
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centers provided data for 550 eligible patients, including 209 patients whose prognostic information was previously unpublished.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.
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.
The authors.
Has not received any funding.
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.