Background
The aim of the present study was to determine whether tumour-specific gene amplification is detectable in circulating cell-free DNA isolated from the plasma of breast cancer patients. Four loci, known to show amplification in breast cancers, were chosen for investigation of paired plasma and tumour DNA: Her-2 and C35 on chromosome 17, and FGFR1 and RAB11f1P1, which map to chromosome 8. Both gene pairs are frequently, but not exclusively, coamplified in breast tumours.