Indeed, CTC cultures derived from patients with metastatic ER+ breast cancer were tested by next-generation sequencing and with a panel of targeted inhibitors, including PI3K, FGF, IGF, and ER targeting drugs, as well as cytotoxic agents, including doxorubicin, paclitaxel, and capecitabine [100]. This evidence concerns the gene ESR1 and breast carcinoma.