Schultheiss Timothy E
Department of Radiation Oncology, City of Hope Cancer Center, 1500 Duarte Road, Duarte, CA 91010, USA.
Int J Radiat Oncol Biol Phys. 2008 Aug 1;71(5):1455-9. doi: 10.1016/j.ijrobp.2007.11.075. Epub 2008 Feb 19.
To characterize the radiation dose-response of the human spinal cord.
Because no single institution has sufficient data to establish a dose-response function for the human spinal cord, published reports were combined. Requisite data were dose and fractionation, number of patients at risk, number of myelopathy cases, and survival experience of the population. Eight data points for cervical myelopathy were obtained from five reports. Using maximum likelihood estimation correcting for the survival experience of the population, estimates were obtained for the median tolerance dose, slope parameter, and alpha/beta ratio in a logistic dose-response function. An adequate fit to thoracic data was not possible. Hyperbaric oxygen treatments involving the cervical cord were also analyzed.
The estimate of the median tolerance dose (cervical cord) was 69.4 Gy (95% confidence interval, 66.4-72.6). The alpha/beta = 0.87 Gy. At 45 Gy, the (extrapolated) probability of myelopathy is 0.03%; and at 50 Gy, 0.2%. The dose for a 5% myelopathy rate is 59.3 Gy. Graphical analysis indicates that the sensitivity of the thoracic cord is less than that of the cervical cord. There appears to be a sensitizing effect from hyperbaric oxygen treatment.
The estimate of alpha/beta is smaller than usually quoted, but values this small were found in some studies. Using alpha/beta = 0.87 Gy, one would expect a considerable advantage by decreasing the dose/fraction to less than 2 Gy. These results were obtained from only single fractions/day and should not be applied uncritically to hyperfractionation.
描述人类脊髓的辐射剂量反应特征。
由于没有单一机构拥有足够的数据来建立人类脊髓的剂量反应函数,因此将已发表的报告进行了合并。所需数据包括剂量与分割方式、处于危险中的患者数量、脊髓病病例数以及人群的生存经验。从五篇报告中获得了八个关于颈髓病的数据点。使用针对人群生存经验进行校正的最大似然估计,得出了逻辑剂量反应函数中的中位耐受剂量、斜率参数和α/β比值的估计值。无法对胸段数据进行充分拟合。还对涉及颈髓的高压氧治疗进行了分析。
颈髓中位耐受剂量的估计值为69.4 Gy(95%置信区间,66.4 - 72.6)。α/β = 0.87 Gy。在45 Gy时,脊髓病的(外推)概率为0.03%;在50 Gy时,为0.2%。脊髓病发生率为5%时的剂量为59.3 Gy。图形分析表明胸髓的敏感性低于颈髓。高压氧治疗似乎有增敏作用。
α/β的估计值比通常引用的要小,但在一些研究中也发现了如此小的值。使用α/β = 0.87 Gy,人们预期通过将每次分割剂量降至小于2 Gy会有相当大的优势。这些结果仅来自每天单次分割,不应不加批判地应用于超分割治疗。