['To investigate the prognostic significance of disseminated tumor cells (DTCs) in bone marrow (BM) from non-metastatic breast cancer patients before and after surgery.', 'Patients with non-metastatic breast cancer were consecutively recruited to this project during the years 1998-2000. Real-time RT-PCR quantification of a DTC multimarker panel consisting of cytokeratin 19, mammaglobin A and TWIST1 mRNA was performed in BM samples obtained from 154 patients three weeks (BM2) and/or six months after surgery (BM3). The results were compared to previously published data from pre-operative BM analyses for the same patients.', 'DTCs were identified in post-operative BM samples (BM2 and/or BM3) from 23 (15%) of the 154 patients investigated. During a median follow-up of 98\u2009months, 10 (44%) of these patients experienced systemic relapse as compared to 16 (12%) of 131 DTC-negative patients. Kaplan-Meier estimates of systemic recurrence-free- and breast-cancer specific survival demonstrated significantly shorter survival for patients with persistent DTCs in BM after surgery (p≤0.001). By multivariate Cox regression analyses, persistent DTCs after surgery was an independent predictor of both systemic recurrence-free- (HR\u2009=\u20095.4, p\u2009<\u20090.001) and breast-cancer specific survival (HR\u2009=\u20095.3, p\u2009<\u20090.001). Furthermore, the prognostic value of DTCs in BM was similar for pre- and post surgery samples. However, patients with DTCs both before and after surgery (BM1 and BM2/3) had a particularly poor prognosis (systemic recurrence-free survival: HR\u2009=\u20097.2, p\u2009<\u20090.0001 and breast-cancer specific survival: HR\u2009=\u20098.0, p\u2009<\u20090.0001).'] Are persistent tumor cells in bone marrow of non-metastatic breast cancer patients after primary surgery associated with inferior outcome?