Recent advances in technologies for the detection of occult metastatic cells in bone marrow of breast cancer patients

The search for occult metastatic cells in patients with small breast tumours, which have been resected with tumour-free margins, has attracted great interest during the past decade. Early tumour cell dissemination is now recognized as a cause of metastatic disease [1,2,3], which is the leading cause of death from cancer in the Western industrialized world. The immunocytochemical search for such disseminated tumour cells in bone marrow was first investigated in breast cancer [4]. It is thus perhaps somewhat ironic that the clinical significance of metastatic breast cancer cells has remained controversial. The discrepant results of clinical follow-up studies are best explained by substantial methodological variations, study populations of insufficient size, and short periods of clinical follow up. Thus, the clinical applications for bone marrow analysis in patients with solid tumours are still controversially discussed [5,6].Regarding methodological heterogeneity, a similar situation occurred in detection and evaluation of minimal residual disease in lymphoma, which, in an international effort, was successfully overcome some 10 years ago [7]. In patients with lymphoma standardized detection procedures now contribute to a refined staging system, resulting in individualized treatment options and an improved outcome for such patients [8]. This example clearly highlights the efforts that are now necessary in order to implement screening for occult metastatic carcinoma cells into current risk classification systems and treatment protocols for patients with breast cancer and other solid tumours. The present commentary focuses on recent advances in technologies for the detection of occult metastatic cells in bone marrow in breast cancer patients.Immunocytochemical and molecular approaches are currently being evaluated for their reliability and clinical utility in detecting isolated metastatic cells in bone marrow of breast cancer patients.Data on bone marrow screening for br