摘要：Background DNA methylation in the BRCA1 promotor region is one of the most important epigenetic silencing mechanisms related to tumorigenesis and breast cancer progression, as well as poorer prognosis. Furthermore, it is a potential indicator for chemotherapy response. We measured the BRCA1 methylation level in various stages of breast cancer and adjacent normal breast tissues using the pyrosequencing method, to investigate correlations between BRCA1 methylation and tumour stage, to study BRCA1 methylation level as a prognostic factor related to overall survival, and to prove that pyrosequencing is an effective and efficient method to quantify methylation levels and can be used as a diagnostic, prognostic, adjuvant therapy decision making, and therapy monitoring tool. Methods 30 breast cancer and 30 adjacent normal breast tissue amples from untreated patients were selected for methylation analysis using pyrosequencing assay for DNA methylation analysis. Findings Cancer tissue showed significantly higher levels of BRCA1 methylation (mean 36.5; median 37) than matched normal breast tissues (mean 7.51; median 7.4) (p = 0.0001). There was no significant relationship between BRCA1 methylation level and tumour stage (stage 1: median 32.3; mean 32.1; SD 1.279; stage 2: median 36.45; mean 36.51; SD 1.42; stage 3+4: median 40.55; mean 40.28; SD 1.526). Interpretation Our results suggest that BRCA1 promotor hypermethylation is an early event of breast cancer carcinogenesis. Pyrosequencing generates highly reproducible quantification of methylation frequencies, providing a short read, rapid measurement and good precision.