Chemoradiotherapy (CRT) is extensively used prior to surgery for rectal cancer to provide significantly better local control, but the radiotherapy (RT), as the other component of CRT, has been subject to less interest than the drug component in recent years. With considerable developments in RT, the use of advanced techniques, such as intensity-modulated radiotherapy (IMRT) in rectal cancer, is garnering more attention nowadays. The radiation dose can be better conformed to the target volumes with possibilities for synchronous integrated boost without increased complications in normal tissue. Hopefully, both local recurrence and toxicities can be further reduced. Although those seem to be of interest, many issues remain unresolved. There is no international consensus regarding the radiation schedule for preoperative RT for rectal cancer. Moreover, an enormous disparity exists regarding the RT delivery. With the advent of IMRT, variations will likely increase. Moreover, time to surgery is also quite variable, as it depends upon the indication for RT/CRT in the clinical practices. In this review, we discuss the options and problems related to both the dose-time fractionation schedule and time to surgery; furthermore, it addresses the research questions that need answering in the future.

中文翻译：

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直肠癌术前放疗的剂量-时间分割方案和手术时机。

放化疗 (CRT) 在直肠癌手术前被广泛使用，以提供更好的局部控制，但放疗 (RT) 作为 CRT 的另一个组成部分，近年来比药物组成部分受到的关注较少。随着放疗技术的长足发展，直肠癌调强放射治疗（IMRT）等先进技术的应用如今受到越来越多的关注。放射剂量可以更好地符合目标体积，并且可以同步积分增强，而不会增加正常组织的并发症。希望局部复发和毒性都能进一步减少。尽管这些似乎很有趣，但许多问题仍未解决。关于直肠癌术前放疗的放射方案尚无国际共识。此外，RT 交付存在巨大差异。随着 IMRT 的出现，变异可能会增加。此外，手术时间也有很大差异，因为它取决于临床实践中 RT/CRT 的适应症。在这篇综述中，我们讨论了与剂量-时间分割时间表和手术时间相关的选择和问题；此外，它还解决了未来需要回答的研究问题。