Presence of bone marrow micrometastasis is associated with different recurrence risk within molecular subtypes of breast cancer.

Expression profiles of primary breast tumors were investigated in relation to disseminated tumor cells (DTCs) in bone marrow (BM) in order to increase our understanding of the dissemination process. Tumors were classified into five pre-defined molecular subtypes, and presence of DTC identified (at median 85 months follow-up) a subgroup of luminal A patients with particular poor outcome (p=0.008). This was not apparent for other tumor subtypes. Gene expression profiles associated with DTC and with systemic relapse for luminal A patients were identified. This study suggests that DTC in BM differentially distinguishes clinical outcome in patients with luminal A type tumors and that DTC-associated gene expression analysis may identify genes of potential importance in tumor dissemination.