Huang Eugene H, Pollack Alan, Levy Larry, Starkschall George, Dong Lei, Rosen Isaac, Kuban Deborah A
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Int J Radiat Oncol Biol Phys. 2002 Dec 1;54(5):1314-21. doi: 10.1016/s0360-3016(02)03742-2.
To identify dosimetric, anatomic, and clinical factors that correlate with late rectal toxicity after three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer.
We retrospectively analyzed the dose-volume histograms and clinical records of 163 Stage T1b-T3c prostate cancer patients treated between 1992 and 1999 with 3D-CRT, to a total isocenter dose of 74-78 Gy at The University of Texas M. D. Anderson Cancer Center. The median follow-up was 62 months (range 24-102). All late rectal complications were scored using modified Radiation Therapy Oncology Group and Late Effects Normal Tissue Task Force criteria. The 6-year toxicity rate was assessed using Kaplan-Meier analysis and the log-rank test. A univariate proportional hazards regression model was used to test the correlation between Grade 2 or higher toxicity and the dosimetric, anatomic, and clinical factors. In a multivariate regression model, clinical factors were added to the dosimetric and anatomic variables to determine whether they significantly altered the risk of developing late toxicity.
At 6 years, the rate of developing Grade 2 or higher late rectal toxicity was 25%. A significant volume effect was observed at rectal doses of 60, 70, 75.6, and 78 Gy, and the risk of developing rectal complications increased exponentially as greater volumes were irradiated. Although the percentage of rectal volume treated correlated significantly with the incidence of rectal complications at all dose levels (p <0.0001 for all comparisons), the absolute rectal volume appeared to be a factor only at the higher doses of 70, 75.6, and 78 Gy (p = 0.0514, 0.0016, and 0.0021, respectively). The following variables also correlated with toxicity on the univariate analysis: maximal dose to the clinical target volume, maximal dose to rectum, maximal dose to the rectum as a percentage of the prescribed dose, and maximal dose delivered to 10 cm(3) of the rectum. Of the clinical variables tested, only a history of hemorrhoids correlated with rectal toxicity (p = 0.003). Multivariate analysis showed that the addition of hemorrhoids increased the risk of toxicity for each dosimetric variable found to be significant on univariate analysis (p <0.05 for all comparisons).
Dose-volume histogram analyses clearly indicated a volume effect on the probability of developing late rectal complications. Therefore, dose escalation may be safely achieved by adherence to dose-volume histogram constraints during treatment planning and organ localization at the time of treatment to ensure consistent patient setup.
确定与前列腺癌三维适形放疗（3D-CRT）后直肠晚期毒性相关的剂量学、解剖学和临床因素。
我们回顾性分析了1992年至1999年间在德克萨斯大学MD安德森癌症中心接受3D-CRT治疗的163例T1b-T3c期前列腺癌患者的剂量体积直方图和临床记录，总等中心剂量为74-78 Gy。中位随访时间为62个月（范围24-102个月）。所有晚期直肠并发症均按照改良的放射治疗肿瘤学组和正常组织晚期效应特别工作组标准进行评分。使用Kaplan-Meier分析和对数秩检验评估6年毒性发生率。采用单变量比例风险回归模型检验2级或更高毒性与剂量学、解剖学和临床因素之间的相关性。在多变量回归模型中，将临床因素添加到剂量学和解剖学变量中，以确定它们是否显著改变发生晚期毒性的风险。
6年时，发生2级或更高直肠晚期毒性的发生率为25%。在直肠剂量为60、70、75.6和78 Gy时观察到显著的体积效应，随着照射体积增大，发生直肠并发症的风险呈指数增加。尽管在所有剂量水平下，接受治疗的直肠体积百分比与直肠并发症的发生率显著相关（所有比较p<0.0001），但绝对直肠体积似乎仅在70、75.6和78 Gy等较高剂量时才是一个因素（分别为p = 0.0514、0.0016和0.0021）。在单变量分析中，以下变量也与毒性相关：临床靶体积的最大剂量、直肠的最大剂量、直肠最大剂量占处方剂量的百分比以及直肠10 cm³接受的最大剂量。在测试的临床变量中，只有痔疮病史与直肠毒性相关（p = 0.003）。多变量分析表明，对于单变量分析中发现显著的每个剂量学变量，合并痔疮会增加毒性风险（所有比较p<0.05）。
剂量体积直方图分析清楚地表明了体积效应与发生直肠晚期并发症概率之间的关系。因此，在治疗计划期间遵守剂量体积直方图限制并在治疗时进行器官定位以确保患者摆位一致，可能安全地实现剂量递增。
