According to the cancer stem cell hypothesis, the few self-renewing stem cells that fuel the cancer are difficult to kil肿瘤干细胞假说认为，用药物很难将这些少量的促使肿瘤产生的可自我复制的肿瘤干细胞杀灭，也许肿瘤干细胞这种耐药性可解析为何经过成功治疗的乳腺癌患者仍会经常复发。