Kitakabu Y, Shibamoto Y, Sasai K, Ono K, Abe M
Department of Radiology, Faculty of Medicine, Kyoto University, Japan.
Int J Radiat Oncol Biol Phys. 1991 Apr;20(4):709-14. doi: 10.1016/0360-3016(91)90013-t.
Variations of the hypoxic fraction (HF) after single dose (13 Gy or 4 Gy) and during fractionated (5 fractions of 4 Gy, 1 or 2 fractions per day) radiation therapy were studied in SCC VII tumors implanted subcutaneously in the hind legs of C3H/He/Jms mice using the paired survival curve method. Whole-body irradiation was delivered to tumor-bearing mice without anesthesia or physical restraint, because both are known to increase the HF artificially. The HF decreased after a single 13 Gy dose in a biphasic fashion: extremely rapidly within 1 hr and comparatively slowly during the following 12-72 hr. On the other hand, nearly no fall of HF was observed in 24 hr following a single 4 Gy dose. Also, reoxygenation was found to occur more rapidly in the interfraction period as the number of fractions of 4 Gy increased irrespective of differences of interfraction time. However, the HF just before each radiation fraction was significantly higher than the pretreatment level for both fractionated regimens. Thus, the reoxygenation patterns observed after single low and high doses of irradiation were different from each other, and reoxygenation in each interfraction period did not always proceed in a similar manner to that after single low dose irradiation. Reoxygenation was facilitated as fractionated radiation therapy proceeded, but it was not sufficient for the HF to remain at a level comparable to that before irradiation.
使用配对生存曲线法，对皮下植入C3H/He/Jms小鼠后腿的SCC VII肿瘤在单次剂量（13 Gy或4 Gy）照射后以及分次（5次4 Gy，每天1或2次）放射治疗期间的低氧分数（HF）变化进行了研究。对荷瘤小鼠进行全身照射时不进行麻醉或身体约束，因为已知这两者都会人为增加HF。单次13 Gy剂量照射后，HF呈双相下降：在1小时内极快下降，在接下来的12 - 72小时内相对缓慢下降。另一方面，单次4 Gy剂量照射后24小时内几乎未观察到HF下降。此外，发现随着4 Gy分次次数的增加，在分次间期再氧合发生得更快，与分次间期时间差异无关。然而，两种分次照射方案中每次放射分次前的HF均显著高于预处理水平。因此，单次低剂量和高剂量照射后观察到的再氧合模式彼此不同，并且每个分次间期的再氧合并不总是以与单次低剂量照射后相似的方式进行。随着分次放射治疗的进行，再氧合得到促进，但HF不足以维持在与照射前相当的水平。
