ESR1 and breast carcinoma: A comparison of ctDNA testing in samples from patients with advanced breast cancer (for mutations in four known drivers in breast cancer: PIK3CA exon 9 and 20, ESR1 ligand binding domain, AKT1, and ERBB2) showed no differences in samples taken in Streck cell-free DNA BCT® tubes that were processed after 48–72 hours compared with samples that were processed immediately [32].