Sakata Koh-ichi, Nagakura Hisayasu, Oouchi Atushi, Someya Masanori, Nakata Kensei, Shido Mitsuo, Koito Kazumitsu, Sagae Satoru, Kudo Ryuichi, Hareyama Masato
Department of Radiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Int J Radiat Oncol Biol Phys. 2002 Dec 1;54(5):1369-76. doi: 10.1016/s0360-3016(02)03055-9.
To examine the incidence of radiation-induced late rectal complications by analyzing the data of measured rectal doses in patients with cancer of the uterine cervix treated with high-dose-rate intracavitary brachytherapy.
We measured doses to the rectum in 105 patients with cancer of the cervix during high-dose-rate intracavitary brachytherapy with a semiconductor dosimeter that can measure five points in the rectum simultaneously. On the basis of these measurements, equivalent doses, to which the biologically equivalent doses were converted as if given as fractionated irradiation at 2 Gy/fraction, were calculated as components of the cumulative dose at five rectal points in intracavitary brachytherapy combined with the external whole pelvic dose.
The calculated values of equivalent doses for late effects at the rectum ranged from 15 to 100 Gy (median 60 Gy for patients who did not develop complications and 76 Gy for patients who subsequently developed Grade II or III complications). When converted to a graph of absolute rectal complication probability, the data could be fitted to a sigmoid curve. The data showed a very definite dose-response relationship, with a threshold for complications at approximately 50 Gy and the curve starting to rise more steeply at approximately 60 Gy. The steepest part of the curve had a slope equivalent to approximately 4% incidence/1 Gy increase in equivalent doses.
The radiation tolerance dose, 5% and 50% complication probability, was about 64 and 79 Gy, respectively. Our data almost agree with the prescribed dose for the rectum for the radiation tolerance doses on the basis of the recorded human and animal data. The probability of rectal complications increased drastically after the maximal rectal dose was >60 Gy.
通过分析高剂量率腔内近距离放射治疗子宫颈癌患者直肠剂量测量数据，研究放射性直肠晚期并发症的发生率。
我们使用能同时测量直肠五个点剂量的半导体剂量仪，在105例子宫颈癌患者高剂量率腔内近距离放射治疗期间测量直肠剂量。基于这些测量结果，计算等效剂量，如同以2Gy/分次的分割照射方式给予时，将生物等效剂量转换为等效剂量，作为腔内近距离放射治疗结合盆腔外照射时直肠五个点累积剂量的组成部分。
直肠晚期效应的等效剂量计算值范围为15至100Gy（未发生并发症患者的中位数为60Gy，随后发生II级或III级并发症患者的中位数为76Gy）。当转换为绝对直肠并发症概率图时，数据可拟合为S形曲线。数据显示出非常明确的剂量反应关系，并发症阈值约为50Gy，曲线在约60Gy处开始更陡峭地上升。曲线最陡峭部分的斜率相当于等效剂量每增加1Gy发生率约增加4%。
放射性耐受剂量，并发症概率为5%和50%时，分别约为64Gy和79Gy。我们的数据几乎与基于已记录的人类和动物数据得出的直肠放射性耐受剂量的规定剂量一致。直肠最大剂量>60Gy后，直肠并发症的概率急剧增加。
