Disseminated tumor cells as a monitoring tool for adjuvant therapy in patients with primary breast cancer.

The presence of disseminated tumor cells (DTC) in the bone marrow (BM) of early breast cancer patients at initial surgery as well as during follow-up predicts an unfavorable outcome. This study aimed to assess whether adjuvant systemic therapy has the ability to eradicate DTC and to determine the clinical impact of DTC-persistence. Between 12 and 24 months after an initial BM aspiration during primary surgery (BMA1) a second and third bone marrow aspiration (BMA2 and BMA3, respectively) was performed. DTC were identified by immunocytochemistry (pancytokeratin antibody A45-B/B3) and cytomorphology. A total of 190 patients who were DTC-positive at BMA1 were eligible for this retrospective analysis. DTC persisted in 35 of 190 (19 %) patients at BMA2 and in 11 of 71 (16 %) patients at BMA3. DTC-persistence at BMA3 was significantly lower in patients that received adjuvant endocrine therapy (p = 0.017). At BMA2, DTC-positive patients were at an increased risk of disease recurrence (HR: 4.17, 95 % CI: 1.51-11.50, p = 0.003) and death (HR: 5.02, 95 % CI: 1.156-21.83, p = 0.031). At BMA3, the presence of DTC was associated with shorter disease free survival (HR: 3.20, 95 % CI: 1.05-9.78, p = 0.010). In conclusion, a majority of initially DTC-positive primary breast cancer patients turned negative during adjuvant treatment. As DTC-persistence predicted an adverse outcome, serial DTC-determination can identify patients that will probably benefit from additional or a switch of adjuvant therapy.