尽管机体内具有一系列的免疫监视 ,但仍难以阻止肿瘤的发生和发展 ,因为肿瘤细胞有多种机制可以逃避人体免疫系统监视 ,如肿瘤表面抗原缺失 ,致使免疫细胞不能识别肿瘤细胞 ,还可以产生多种免疫抑制因子以降低宿主免疫力等 ,特别是老年患者 ,随着衰老和免疫抵抗力的下降 ,肿瘤 Although the body has a series of immune surveillance, but it is still difficult to prevent the occurrence and development of tumors, because tumor cells have a variety of mechanisms to evade the human immune system surveillance, such as the lack of tumor surface antigen, resulting in immune cells can not identify tumor cells, Produce a variety of immunosuppressive factors to reduce host immunity, especially in elderly patients, with the decline of aging and immune resistance, cancer