Prognostic impact of baseline circulating tumor cells (CTCs) detected by the isolation by size of epithelial tumor cells (ISET) in locally advanced head and neck squamous cell carcinoma (LAHNSCC): Results of a prospective study.

Abstract

6061 Background: The prognostic impact of CTCs in LAHNSCC is yet to be determined, with conflicting results in previous trials, the majority utilizing cytokeratin dependent techniques for identification and counting of CTCs. The primary objective of this study is to determine the detection rates using the ISET method, and the prognostic role of CTCs in LAHNSCC patients (pts) treated with a curative intent. Methods: In this prospective study, peripheral blood samples of pts with non-metastatic LAHNSCC, stages III/IV, were analyzed for CTCs using the ISET method, in two scenarios: curative surgical resection and adjuvant radiotherapy (CTCs before RT) and candidates for a non-surgical strategy (unresectable or organ preservation) either with upfront RT concurrent with chemotherapy (CT) or cetuximab (CTCs before RT), or preceded by induction CT (CTCs before ICT). Results: Eighty-three pts were included, the majority males (83%), with oropharynx primary (50%) and submitted to ICT (40%). The detection rate of baseline CTCs was 94% (78/83), and CTCs counts were significantly correlated with survival. For each increase of 1 CTC at baseline there was a relative increase of 18% in the risk of death (HR = 1.18; 95%CI: 1.06-1.31; p < 0.001), 16% in the risk of progression (HR = 1.16; 95%CI: 1.04-1.28; p = 0.004) and a reduction of 26% in the odds of complete response to treatment (non-surgical group only - OR = 0.74; 95%CI: 0.58-0.95; p = 0.022). Using the maximum of the standardized log-rank statistic proposed by Lausen and Schumacher we establish cut off points for overall survival (OS) and progression-free survival (PFS). Pts with CTCs < 6.5/ml had an estimated 2y OS of 85.6% versus 22.9% for CTCs ≥ 6.5/ml (HR = 0.18; 95%CI: 0.06-0.49; P < 0.0001) and pts with CTCs ≤ 3.8/ml had an estimated 2y PFS of 71.8% versus 37% for CTCs > 3.8/ml (HR = 0.32; 95%CI:0.15-0.67; p = 0.001). Conclusions: The detection rate of baseline CTCs using the ISET method was very high in LAHNSCC and the counts of CTCs were strongly correlated with survival and response to treatment.