Humm J L
MRC Radiobiology Unit, Chilton, Didcot, Oxon, U.K.
Int J Radiat Oncol Biol Phys. 1987 Nov;13(11):1767-73. doi: 10.1016/0360-3016(87)90176-3.
Astatine-211 is an alpha-emitter with a short half-life (7.2 hr). This paper discusses the potential of 211At targeted by antibodies for tumor therapy and the possible advantage of 211At over beta- and gamma-emitting radionuclides such as 131I currently employed in the field of radioimmunotherapy. Since the longest range alpha-particle from 211At is only 67 microns and the rate of energy loss is high (track averaged linear energy transfer LT approximately 120 keV/micron), a disintegration of 211At produces a large and extremely localized deposition of energy. A Monte-Carlo model has been developed for studying the stochastic fluctuation of alpha-particle hits and energy deposition in cell nuclei in an attempt to determine the efficacy of 211At-labeled antibodies for tumor cell inactivation. Calculations have been performed for 2 extreme conditions: (a) the case of 211At retained in the capillary, and (b) for a homogeneous distribution of 211At-labeled antibody in the tumor. The results of these two calculations represent the boundary conditions between which any real solution must lie. Finally, developments to the model to include antibody transport across the capillary membrane and through the tumor tissue are discussed.
砹-211是一种半衰期较短（7.2小时）的α发射体。本文讨论了用抗体靶向的211At在肿瘤治疗中的潜力，以及211At相对于目前放射免疫治疗领域中使用的β和γ发射放射性核素（如131I）可能具有的优势。由于来自211At的最长射程α粒子仅为67微米，且能量损失率很高（径迹平均线能量转移LT约为120 keV/微米），211At的一次衰变会产生大量且极其局部化的能量沉积。已开发出一个蒙特卡罗模型，用于研究α粒子撞击和细胞核内能量沉积的随机波动，以确定211At标记抗体使肿瘤细胞失活的功效。针对两种极端情况进行了计算：（a）211At保留在毛细血管中的情况，以及（b）211At标记抗体在肿瘤中均匀分布的情况。这两种计算结果代表了任何实际解决方案都必须介于其间的边界条件。最后，讨论了对该模型的改进，以纳入抗体穿过毛细血管膜和通过肿瘤组织的传输过程。
