ESR1 and breast cancer: The ctDNA mutation frequencies of the TP53, PIK3CA, and ESR1 genes were 37.8% (95% CI: 25.4–52.1%), 26.6% (22.4–31.2%) and 32.4% (26.8–38.5%) in the 11,19, and 10 studies consisting of 338, 1015 and 1379 patients with BC, respectively.[4,6,8,13,19,23–25,29,35–38,44–46,49,53–56,60,63,64,66,67,69] Among the studies that presented the frequency of ctDNA mutations in the TP53 and PIK3CA genes, eleven and nineteen studies were able to distinguish between patients with early surgery and patients with metastasis.