Lindegaard J C, Grau C, Overgaard J
Danish Cancer Society, Department of Experimental Clinical Oncology, Aarhus.
Int J Radiat Biol. 1991 Oct;60(4):707-21. doi: 10.1080/09553009114552511.
The effect of step-down heating (SDH) on the interaction between heat and radiation was investigated in a C3H mammary carcinoma in vivo. SDH consisted of an initial sensitizing treatment (ST) performed at 44.5 degrees C or 43.5 degrees C followed by a lower temperature test treatment (TT) in the range 41.0-43.0 degrees C. Step-up heating (SUH), i.e. TT followed by ST, and single heating were used as controls. The end-point was the radiation dose needed to control 50% of the tumours (TCD50). The results were evaluated by calculating the thermal enhancement ratio (TER) defined as TER = TCD50 (radiation alone)/TCD50 (radiation and heat). For a simultaneous application of TT and radiation a significant enhancement of direct heat radiosensitization was observed with increasing ST time or ST temperature using SDH. In contrast, only a minor increase was seen with SUH. A comparison between TCD50 values for the corresponding SUH and SDH schedules revealed that the SDH effect was largest at 41.0-42.0 degrees C and decreased with increasing TT temperature. The radiosensitizing effect of SDH also decreased if an interval was allowed between ST and TT or between TT and radiation. However, as a result of an increased cytotoxicity towards hypoxic tumour cells, the TCD50 value for SDH remained significantly smaller than for SUH, even with a sequential combination of radiation and heat.
在C3H乳腺癌体内模型中研究了逐步降温加热（SDH）对热与辐射相互作用的影响。SDH包括在44.5℃或43.5℃进行的初始致敏治疗（ST），随后是41.0 - 43.0℃范围内的较低温度测试治疗（TT）。升温加热（SUH），即TT后接ST，以及单次加热作为对照。终点是控制50%肿瘤所需的辐射剂量（TCD50）。通过计算热增强比（TER）来评估结果，TER定义为TER = TCD50（仅辐射）/TCD50（辐射和热）。对于同时应用TT和辐射的情况，使用SDH时，随着ST时间延长或ST温度升高，直接热放射增敏作用显著增强。相比之下，SUH仅观察到轻微增加。相应的SUH和SDH方案的TCD50值比较表明，SDH效应在41.0 - 42.0℃时最大，并随着TT温度升高而降低。如果在ST与TT之间或TT与辐射之间留出间隔，SDH的放射增敏作用也会降低。然而，由于对缺氧肿瘤细胞的细胞毒性增加，即使采用辐射和热的序贯联合，SDH的TCD50值仍显著小于SUH的TCD50值。
