The role of disseminated and circulating tumour cells in breast cancer

Abstract

Occult dissemination of tumour cells in patients with operable breast cancer is a crucial step in formation of metastasis, yet conventional tumour staging does not reveal it. To identify individual tumour cells that have successfully escaped from the primary tumour and invaded secondary organs, several research groups established sensitive immunocytochemical and molecular assays. Aside of the well documented prognostic impact of lymph node metastasis and micrometastases, respectively, bone marrow plays a prominent role as a determinant for haematogenous micrometastatic organ involvement. In the past decade, several groups have documented the independent prognostic impact of the presence of bone marrow micrometastases, which, in a recent pooled analysis of individual patient data from over 4000 breast cancer patients with Stage I–III disease, could be confirmed for the entire study population, and, in addition, provided data for challenging hypotheses to be tested in future adjuvant therapy trials of clinically relevant subgroups of breast cancer patients. Although the availability of a simple blood test would be highly desirable, no prognostically relevant data so far exists for early breast cancer patients. Options for the applicability of such approaches to detect disseminated (to bone marrow) and circulating tumour cells (in blood) are ample, both in clinical trial settings and for basic as well as translational research. In this overview we provide a brief summary of the prognostic role and the potential clinical utility of bone marrow micrometastases in breast cancer patients.