Disseminated tumor cells: are they ready for clinical use?

During the past three decades, efforts successfully established the presence of disseminated tumor cells (DTC) in bone marrow as a prognostic factor. These works were comprehensively evaluated in a pooled analysis that now permits to classify the prognostic significance of DTC as level I evidence. Intriguing molecular data suggest a role for tumor stem cells possibly responsible for the prognostic impact of DTC. In a typical clinical setting of the year 2007, DTC--irrespectively of the strong prognostic significance--would only have a convincing clinical application if DTC were a surrogate marker for treatment efficacy. Consequently, this important question is to be addressed in well-designed clinical trials.