In the first third of this century, the prevailing concept was that malignant cells had a brief period of sensitivity and radiation treatments were ideally given in overall times of 2 weeks or less. Following the Second World War, routine treatment times were extended to 5 to 8 weeks to avoid severe acute normal tissue reactions and achieve higher tumor doses. In reaction to these prolonged overall times, a series of large-fraction, shortened-overall-time clinical experiments were attempted, with disastrous normal tissue effects and poor tumor control. More recently, attempts to accelerate treatment have been accomplished by utilizing multiple fractions per day or semicontinuous irradiation. Unfortunately, the majority of these attempts have been forced by the occurrence of unacceptable normal tissue reactions to significantly reduce total dose or introduce lengthy splits in treatment. These results suggest that in our current state of knowledge accelerated schedules be reserved for use in the treatment of rapidly proliferating neoplasms or for palliation.
在本世纪的前三分之一时间里，普遍的观念是恶性细胞有一段短暂的敏感时期，放射治疗理想的总时长为2周或更短。第二次世界大战之后，常规治疗时长延长至5至8周，以避免严重的急性正常组织反应并实现更高的肿瘤剂量。针对这些延长的总时长，人们尝试了一系列大分割、缩短总时长的临床试验，但正常组织出现了灾难性的反应，肿瘤控制效果也不佳。最近，通过每天多次分割照射或半连续照射来加速治疗的尝试已经完成。不幸的是，这些尝试中的大多数都因出现了不可接受的正常组织反应而被迫大幅降低总剂量或在治疗过程中引入长时间的中断。这些结果表明，就我们目前的认知水平而言，加速治疗方案应保留用于治疗快速增殖的肿瘤或用于姑息治疗。
