Abstract P1-01-05: Prognostic values of circulating tumor cells (CTC) and cancer associated macrophage-like cells (CAML) enumerations in metastatic breast cancer: The role for innate immunity in the metastatic process

Abstract

Abstract Background: The enumeration of circulating tumor cells (CTCs) using the CellSearch assay is a well-established prognostic and predictive marker for metastatic breast cancer (MBC). However, additional prognostic markers are lacking in patients with ≥ 5 CTCs in 7.5 ml of blood. Tumor-associated macrophages (TAMs) are derived from circulating monocytes or tissue-resident macrophages. TAMs have a controversial role in metastasis and anti-tumor processes. Recent studies showed that circulating cancer associated macrophage-like cells (CAMLs) are specialized phagocytic myeloid cells and found in the peripheral blood of patients with solid tumors including breast cancer, but not in healthy individuals. The presence of CAMLs may indicate the activation of innate immunity in cancer patients. The function and prognostic value of CAMLs in MBC is unknown. In the current study, we measured CTCs and CAMLs on the CellSearch™ platform and investigated their prognostic values in MBC. Methods: Peripheral blood samples from 127 stages IV breast cancer patients were collected at baseline before starting first-line therapy. The detection and enumeration of CTCs and CAMLs in 7.5 ml blood sample were performed on the CellSearch™ system. CTCs were identified by cytokeratins (CK-8, 18, and 19) positive and CD45 negative staining. CAMLs were defined by positive staining for cytokeratins and CD45 (Adams et al, PNAS, 111(9):3514-9, 2014). CTCs and CAMLs enumeration in associations with the progression-free survival (PFS) and overall survival (OS) of patients were evaluated using Kaplan Meier curves and Cox proportional hazards modeling. Results: The image review of CAMLs by using CellSearch analysis showed heterogeneous morphological phenotypes. CAMLs are large cells presenting enlarged nuclei or multiple individual nuclei, and both cytokeratin and CD45 positive with diffused cytoplasmic staining. Among the 127 MBC patients, 38 (29.9%) had elevated CTCs (≥5 CTCs), and 21 (16.5%) had at least one CAML detected. Patients with CAMLs had a significantly increased PFS (p=0.0374) and OS (p=0.0042), compared to patients without CAMLs at baseline. Patients with elevated baseline CTCs and CAMLs had worse PFS with a hazard ratio (HR) of 4.04 (95% CI 2.16 -7.56, P<0.0001), compared to patients with < 5 CTCs and without CAMLs. The combined analysis of baseline CTCs enumeration and CAMLs showed similar effect on patient OS. Compared to patients with < 5 CTCs and without CAMLs, patients with < 5 CTCs and with CAMLs, patients with ≥ 5 CTCs and without CAMLs, and patients with ≥ 5 CTCs and with CAMLs, had an increasing trend of death risk, with an HR of 2.66 (95% CI 0.53-13.21), 6.14 (2.10-17.92), and 9.13 (3.05-27.37), respectively (p for trend<0.0001). Conclusion: Baseline enumerations of both individual CTCs and CAMLs are feasible and increase our ability to accurately predict outcome in MBC patients. Evaluation of CAMLs in peripheral blood may be a marker of innate immunity and provide additional prognostic values for MBC. Citation Format: Mu Z, Wang C, Ye Z, Rossi G, Austin L, Yang H, Cristofanilli M. Prognostic values of circulating tumor cells (CTC) and cancer associated macrophage-like cells (CAML) enumerations in metastatic breast cancer: The role for innate immunity in the metastatic process [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-01-05.