Combined peripheral natural killer (NK) cell and circulating tumor cell (CTC) enumeration to enhance prognostic efficiency in patients (pts) with triple-negative breast cancer (TNBC).

Abstract

1105 Background: CTCs have emerged as an independent prognostic factor for metastatic breast cancer. However, the prognostic value of baseline CTCs regarding PFS in TNBC is still controversial, especially beyond first-line. We evaluated a novel combined NK cell/CTC detection system for enumeration to better understand the impact of cell count on prognosis in TNBC. Methods: 83 consecutive patients with metastatic TNBC were enrolled and received a new line of therapy (median=2, range: 1~5). Baseline circulating CTCs and NK cells were isolated and enumerated simultaneously prior to starting a new line of therapy using our previously published method targeting EpCAM (Bai et al. J Mater Chem B, 2014) and flow cytometry (antibodies against CD3-, CD45+, CD56+) respectively. The NK cell level was expressed as the proportion of total lymphocytes (%). Patients with normal to high NK cell proportion (≥ 9.15%) and > 2 CTC/2 ml were defined as NK resistant CTC, the rest were defined as non-NK resistant CTC. Results: 33 out of 83 TNBCs had first-line of therapy. Pts with ≤ 2 CTC/2 ml had a significantly longer median PFS than those with > 2 CTC/2 ml ( P = 0.028). The differences in median PFS were not significant ( P=0.110) for the entire group of pts with TNBC receiving different lines of therapy. Pts with non-NK resistant CTCs had a significantly longer median PFS than those with NK resistant CTCs ( P= 0.025), regardless of line of therapy. Conclusions: Including peripheral NK cell level into consideration can improve CTC prognostic efficiency in predicting PFS for TNBCs receiving different line of therapy. Further analysis of the unique biological features of NK-resistant CTCs and associated clinical consequence holds promise in guiding clinical practice. [Table: see text]