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对大块肿瘤成功的放疗需克服晚期肿瘤的乏氧放射抵抗性。放射治疗的对象是局部大肿块肿瘤和区域扩散的肿瘤。采用常规方式和剂量治疗T_1或小的肿瘤(小于2厘米),或是显微镜下病变,可以在正常组织耐受性限度内控制肿瘤。但对T_2肿瘤则常有失败,对T_2和T_4肿瘤几乎无法治愈。对于大块肿瘤,可以用增加光子剂量的方法来提高肿瘤控制可能性,但这样就会出现正常组织损伤的问题。如果所给的剂量超过了正常组织耐
Successful radiotherapy of large tumors needs to overcome the hypoxic radioresistance of advanced tumors. The object of radiotherapy is a local large mass tumor and a regionally spread tumor. Treatment of T_1 or small tumors (less than 2 cm) or lesions under the microscope in the usual way and with doses can control tumors within the limits of normal tissue tolerance. However, it is often unsuccessful for T 2 tumors and almost incurable for T 2 and T 4 tumors. For large tumors, the possibility of tumor control can be increased by increasing the photon dose, but this can lead to problems with normal tissue damage. If the given dose exceeds normal tissue resistance