Although resistant forms are commonly found in tumors that haven’t yet been exposed to treatment, they generally occur in small numbers. This suggests that resistant cells are not so unfit that drug-sensitive cells completely out-competed them, but that they struggle to proliferate when both types are present.
虽然抗药细胞在从未接受过治疗的肿瘤中也十分常见，但它们的数量通常很小。这种现象表明抗药细胞并没有被对药物敏感的细胞彻底击溃，而是在两种细胞混合的情况下竭力扩张。