Abstract

Introduction

The combination of hyperthermia with low LET (linear energy transfer) radiation may have similar anti-tumor effects as high LET radiation alone. This pre-clinical study determined the optimal heating temperature and time interval between radiation and heat to achieve this equivalent effect.

Methods

C3H mammary carcinomas (200 mm³ in size) growing in the right rear foot of CDF1 mice was used in all experiments. Tumors were locally irradiated with graded doses of either 240 kV ortho- or 6 MV mega-voltage X-rays to produce full dose-response curves. Heating (41.0–43.5 °C; 60 min) was achieved by immersing the tumor bearing foot in a water-bath applied at the same time, or up to 4-hours after, irradiating. The endpoint was the percentage of mice showing local tumor control at 90 days, with enhancements calculated from the ratios of the radiation doses causing 50% tumor control (± 95% confidence intervals).

Results

Previous published results in this tumor model reported that carbon ions were 1.3–1.7 times more effective than low LET radiation at inducing tumor control. Similar enhancements occurred with a temperature of only 41.0 °C with a simultaneous heat and radiation treatment. However, higher temperatures were needed with the introduction of any interval; at 42.5 °C, the enhancement was 2.5 with a simultaneous treatment, decreasing to a value within the carbon ion range with a 4-hour interval.

Conclusions

Combining hyperthermia with low LET radiation can be as effective as high LET at inducing tumor control, but the temperature needed depended on the time interval between the two modalities.

中文翻译：

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热疗与低LET（线性能量转移）辐射的组合是否会产生与仅高LET辐射所见的抗肿瘤效果相同的抗肿瘤作用？

摘要

介绍

热疗与低LET（线性能量转移）辐射的组合可能具有与单独高LET辐射相似的抗肿瘤作用。这项临床前研究确定了最佳的加热温度以及辐射和热量之间的时间间隔，以达到相同的效果。

方法

在所有实验中均使用在CDF1小鼠右后脚生长的C3H乳腺癌（大小为200 mm ³）。用240 kV正交或6 MV兆伏电压X射线分级照射局部肿瘤，以产生完整的剂量反应曲线。加热（41.0–43.5°C； 60分钟）是通过将肿瘤支撑脚浸入同时或照射后4小时内的水浴中来实现的。终点是在90天时显示出局部肿瘤控制的小鼠的百分比，并根据引起50％肿瘤控制（±95％置信区间）的放射剂量的比例计算出增强值。

结果

该肿瘤模型的先前发表的结果报告说，碳离子在诱导肿瘤控制方面比低LET辐射有效1.3-1.7倍。在仅41.0°C的温度下，同时进行热处理和辐射处理，会产生类似的增强效果。但是，随着间隔的增加，需要更高的温度。在42.5°C下，同时处理的增强为2.5，以4小时为间隔降低到碳离子范围内的值。

结论

将高热与低LET辐射相结合可以在诱导肿瘤控制方面与高LET一样有效，但是所需的温度取决于两种方式之间的时间间隔。