Research article
Comparative evaluation of cell-free tumor DNA in blood and disseminated tumor cells in bone marrow of patients with primary breast cancer
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* Corresponding author: Heidi Schwarzenbach hschwarz@uke.uni-hamburg.de
1 Institute of Tumor Biology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, Hamburg, 20246, Germany
2 Department of Gynecology and Obstetrics, University of Duisburg-Essen, Sabinastrasse 20, Essen, 45136, Germany
3 Institute of Pathology, University of Duisburg-Essen, Sabinastrasse 20, Essen, 45136, Germany
Breast Cancer Research 2009, 11:R71 doi:10.1186/bcr2404
Published: 21 September 2009Abstract
Introduction
The origin and clinical relevance of circulating cell-free tumor DNA in the blood of cancer patients is still unclear. Here we investigated whether the detection of this DNA is related to bone marrow (BM) micrometastasis and tumor recurrence in breast cancer patients.
Methods
BM aspirates of 81 primary breast cancer patients were analyzed for the presence of disseminated tumor cells (DTC) by immunocytochemistry using the pan-cytokeratin antibody A45-B/B3. PCR-based fluorescence microsatellite analysis was performed for detection of loss of heterozygosity (LOH) at 6 polymorphic markers using cell-free serum DNA. The data were correlated with established risk factors, and patients were followed-up over 6-10 years.
Results
LOH was detected in 33.5% of blood samples. The occurrence of LOH at the entire microsatellite marker set correlated with histopathology (P = 0.05) and grading (P = 0.006) of the primary tumor. The genomic region characterized by marker D9S171 was only affected by LOH in patients with increased tumor stages (pT2-4, P < 0.05) and older age (≥ 55 years, P = 0.05). Kaplan-Meier analysis showed that LOH at D3S1255 (P = 0.009) and D9S171 (P = 0.001) were significantly associated with tumor relapse. In BM, DTC were detected in 39.5% of the patients, and this finding correlated with distant metastases (P < 0.05). Patients with DTC-positive BM had higher DNA yields in their blood than patients with DTC-negative BM (P < 0.05). However, no significant correlations were found between the presence of DTC in BM and the detection of marker-specific LOH on blood DNA.
Conclusions
The detection of LOH on cell-free tumor DNA in blood is unrelated to BM micrometastasis and provides independent information on breast cancer progression.