Ono K, Masunaga S, Akuta K, Akaboshi M
Radiation Oncology Research Laboratory, Kyoto University Research Reactor Institute, Osaka, Japan.
Int J Radiat Oncol Biol Phys. 1994 Apr 30;29(1):81-5. doi: 10.1016/0360-3016(94)90229-1.
Carbogen increases the radiation response of tumors and reduced dose rate irradiation spares the damage of normal tissues. The purpose in this paper is to investigate the possibility of selective radiosensitization of tumors by reduced dose rate irradiation in combination with carbogen inhalation.
SCCVII tumors in C3H/He mice were irradiated at middle dose rate (0.1 Gy/min) or high dose rate irradiation (3.0 Gy/min) in combination with carbogen inhalation. The mice were enclosed in a box with carbogen flushing at 1.01/min. The tumor response was measured by a cytokinesis block micronucleus assay. The effects on intestinal crypt cells and bone marrow cells were investigated by microcolony assay or Hendry's method, respectively.
The anti-tumor effect of middle dose rate irradiation was equal to that of a high dose rate irradiation. Carbogen inhalation, more efficiently, increased the antitumor effect when combined with middle and high dose rate irradiation, and yielded enhancement ratios of 1.6 at around 2 Gy. Middle dose rate irradiation produced less damage on intestinal crypt cells and bone marrow cells in comparison with high dose rate irradiation, and carbogen inhalation never enhanced the responses of these normal tissues in combination with middle dose rate irradiation. Dose modifying factors were 1.3-2.0.
Since middle dose rate irradiation in combination with carbogen inhalation gave the therapeutic gain factors of 2.0-3.2, which were much larger than those obtained with any other radiosensitizers, this combination has a potential as a new modality for improving the results of cancer radiotherapy.
卡波金可增强肿瘤的辐射反应，而低剂量率照射可减轻正常组织的损伤。本文旨在研究低剂量率照射联合吸入卡波金实现肿瘤选择性放射增敏的可能性。
对C3H/He小鼠的SCCVII肿瘤进行中等剂量率（0.1 Gy/分钟）或高剂量率（3.0 Gy/分钟）照射，并联合吸入卡波金。将小鼠置于一个以1.0升/分钟的速度冲洗卡波金的箱子中。通过胞质分裂阻断微核试验测量肿瘤反应。分别通过微集落试验或亨德里方法研究对肠隐窝细胞和骨髓细胞的影响。
中等剂量率照射的抗肿瘤效果与高剂量率照射相当。联合中等剂量率和高剂量率照射时，吸入卡波金能更有效地增强抗肿瘤效果，在约2 Gy时增效比为1.6。与高剂量率照射相比，中等剂量率照射对肠隐窝细胞和骨髓细胞的损伤较小，且联合中等剂量率照射时，吸入卡波金不会增强这些正常组织的反应。剂量修正因子为1.3 - 2.0。
由于中等剂量率照射联合吸入卡波金产生的治疗增益因子为2.0 - 3.2，远大于使用任何其他放射增敏剂所获得的增益因子，因此这种联合方案有潜力成为改善癌症放射治疗效果的新方法。
