Carl U M
Abteilung für gynäkologische Radiologie, UKE, Hamburg.
Strahlenther Onkol. 1993 Oct;169(10):608-11.
A number of experimental investigations has demonstrated, that tumor growth delay due to a mixed fractionated treatment schedule with photons and neutrons can be prolonged compared to pure photon treatment. That question after the mechanisms remains undissolved. In the presented study of the R1H tumor of the rat 30 fractions using 2 Gy of photons in 39 days are compared to results of mixed fractionated treatment schedules with neutrons and photons. Neither a prolonged net growth delay (NGD) was found nor does the sequence in which neutrons and photons are given influence the outcome when replacing photons by neutrons in twelve of 30 fractions (RBE 2.5). In contrast, hypofractionated schedules (five fractions/total dose 40 Gy/four days) have a considerable longer NGD when replacing two fractions of photons by neutrons (RBE 2.5) (p < 0.01). This could be explained if 8 Gy photons/fraction destroyed all euoxic tumor cells, a 24 hour interval was too short for reoxygenation and thus make hypoxia to a major problem in 8 Gy/fraction photon treatment.
多项实验研究表明，与单纯光子治疗相比，采用光子和中子混合分次治疗方案可延长肿瘤生长延迟时间。关于其机制的问题仍未解决。在本项针对大鼠R1H肿瘤的研究中，将39天内使用2 Gy光子进行30次分割的治疗结果与中子和光子混合分次治疗方案的结果进行了比较。既未发现净生长延迟（NGD）延长，在30次分割中有12次将光子替换为中子（相对生物效应2.5）时，给予中子和光子的顺序也不影响结果。相比之下，在将两次分割的光子替换为中子（相对生物效应2.5）时，大分割方案（五次分割/总剂量40 Gy/四天）的NGD显著更长（p < 0.01）。如果每次分割8 Gy光子能破坏所有富氧肿瘤细胞，24小时间隔对于再氧合来说太短，从而使缺氧成为每次分割8 Gy光子治疗中的一个主要问题，那么这一点就可以得到解释。
