High levels of
DNA and
RNA released by apoptotic and necrotic cells circulate in the blood of
cancer patients. In the present study we determined the applicability of the quantification of
nucleic acids and their genetic alterations as minimally invasive tool for
breast cancer screening. The relative concentrations of
DNA and
RNA were determined in preoperative serum of 102
breast cancer patients, 32 patients with benign
breast disease and 53 healthy women. The mean follow-up time of the
cancer patients was 6.2 years. Loss of heterozygosity (LOH) at four polymorphic markers (D13S159, D13S280, D13S282 at region 13q31-33 and D10S1765 at PTEN region 10q23.31) was analyzed by PCR-based fluorescence microsatellite analyses using
cell-free DNA. The serum levels of
DNA (p = 0.016) and
RNA (p = 0.001) could differentiate between healthy women and
cancer patients, but could not discriminate malignant from benign breast lesions. A significant correlation of serum
DNA with
RNA levels was observed in all groups (p = 0.018). Increased serum
DNA levels (but not
RNA levels) in
cancer patients were associated with a poorer overall (p = 0.021) and disease-free survival (p = 0.025). The occurrence of LOH at all markers significantly correlated with lymph node status (p = 0.026). In addition, the LOH frequency at D13S280 (p = 0.047) and D13S159 (p = 0.046) associated with overall and disease-free survival, respectively. In conclusion, the quantification of cell-free tumour
DNA had diagnostic and prognostic values in
breast cancer patients, and
DNA loss at the region 13q31-33 may be an indication of lymphatic tumour cell spread.