对于肿瘤治疗工作的努力主要在于破坏已经形成的恶性变细胞,其次是防止环境致癌物与易感组织的接触。关于在细胞接触致癌物质至细胞转变为恶性期间,如何进行预防的研究工作不多。最近美国一个维生素A工作组提出维生素A可能干扰接触致癌物的细胞转变的进展,并使之恢复正常。一般认为肿瘤的发生要通过三个阶段——开端、瘤形成前期和变形期。在开端,致癌物质作用于一个或几个细胞,使之产生可导致比较持久性的恶性变化(例 Efforts for cancer treatment are mainly to destroy the already formed malignant cells, followed by the prevention of environmental carcinogens and susceptible tissue contact. There are not many studies on how to prevent cell-to-cell carcinomas until they become malignant. Recently, a working group of vitamin A in the United States proposed that vitamin A might interfere with the progression of cell transformation in contact with carcinogens and return it to normal. Generally believed that the occurrence of the tumor through three stages - the beginning, tumor formation and deformation period. At the outset, carcinogens act on one or a few cells to produce a vicious change that leads to more permanent