[Importance of occult metastatic cells in the treatment of patients with breast and gastrointestinal cancers].

Early and clinically non-apparent hematogenous dissemination of tumor cells is considered an important prognostic factor and marker of tumor progression. This phenomenon is reported for tumor entities differing as much as breast and gastrointestinal cancers. First prospective studies point to the unique opportunity of therapy monitoring utilizing follow-up bone marrow aspirations before and after adjuvant therapy. First results of these studies further indicate that currently used treatment strategies such as chemotherapy may not be efficient enough to eliminate all metastatic cells in all of the cases studied. Apart from improved tumor staging, such screening efforts may not only help to improve planning and monitoring of adjuvant therapy (which at present is only possible retrospectively) but also help to design individualized targeted biological treatment. This review summarizes the currently available data on the importance of disseminated tumor cells for the treatment of patients with breast or gastrointestinal cancer.