Sequence of Primary ER+ Breast Tumors Treated with 5 Years of Tamoxifen

Targeted massively parallel sequencing analysis was conducted on DNA extracted from archived 22-28 year old, formalin-fixed primary breast tumors from 625 patents from British Columbia treated with five years of adjuvant tamoxifen monotherapy and followed for over 10 years. Genes were selected for targeted sequencing by review of existing large-scale breast cancer sequencing studies and breast cancer literature. In total, 83 genes were identified and 3,029 probes were designed to tile across all known exons. Illumina sequencing libraries were constructed, indexed, pooled, and enriched for target sequences by hybrid-capture followed by sequencing of paired-end 100bp reads. All samples met minimum quality controls of 80% targeted space covered at 20X or greater. On average, each sample had 336M aligned bases and a mean coverage of 135.8X.]]> The study was based on formalin-fixed paraffin embedded (FFPE) primary tumor blocks from female patients diagnosed with estrogen receptor positive invasive breast cancer in the province of British Columbia in Canada between 1986 and 1992. Patients were treated with five years of adjuvant tamoxifen, no chemotherapy, and followed for breast cancer specific survival and relapse free survival.]]>