Clinical significance of isolated tumor cell detection in peripheral blood in breast cancer patients three years after diagnosis. Comparison between analysis of peripheral blood and bone marrow

Abstract

9554 Background: The detection of isolated tumor cells (ITC) in bone marrow (BM) in breast cancer by immunocytochemical (ICC) methods predicts future systemic relapse and death. Peripheral blood (PB) is easier to obtain than BM, but the clinical significance of ITC detection in PB is still not settled. The analysis of the same number of mononuclear cells (MNC) in PB as for BM results in a markedly lower number of ITC-positive samples. Analysing larger numbers of PBMNC can possibly improve the clinical significance of ITC-detection. This principle was tested and compared to the standard BM analysis by ICC. Methods: Peripheral blood and BM were collected from early breast cancer patients 40 months (median) after operation. Peripheral blood MNC were analysed by a negative immunomagnetic technique (10x106 cells/test) followed by ICC. Bone marrow aspirates from the same patients were analysed by a standard direct ICC method (2x106 cells/test). Results: Of the 96 node-positive patients analysed so far, 18 had ITC in PB by negative IMS (19%). In BM, 21% of the patients were positive (20/96). Seven patients were positive both in PB and BM (7%). After median 63 months FU from diagnosis, 16 systemic relapses and 10 breast cancer deaths have occurred. Systemic relapse and breast cancer death were observed in 33% and 28% of the patients with ITC-positive cells in PB, as compared to 13% and 6% in the ITC-negative cases, respectively. For the BM analysis, 35% and 25% of the ITC-positive and 12% and 7% of the ITC-negative patients experienced systemic relapse and breast cancer death. Kaplan Meier analyses show that ITC-detection in PB is associated with reduced breast cancer specific survival (p<0.001) and distant disease free survival (p=0.016, log-rank test). Patients with ITC in both PB and BM had an especially poor prognosis. Conclusions: Detection of ITC in larger volumes of PB can be used for selection of patients with an unfavourable clinical outcome and should be considered as a tool for monitoring occult tumor cells. No significant financial relationships to disclose.