Institute of Cancer Research, UK.
Radiother Oncol. 2012 Aug;104(2):205-12. doi: 10.1016/j.radonc.2012.07.005. Epub 2012 Aug 8.
An unexpected finding from the phase III parotid sparing radiotherapy trial, PARSPORT (ISRCTN48243537, CRUK/03/005), was a statistically significant increase in acute fatigue for those patients who were treated with intensity-modulated radiotherapy (IMRT) compared to standard conventional radiotherapy (CRT). One possible explanation was the difference in dose to central nervous system (CNS) structures due to differing beam portals. Using data from the trial, a dosimetric analysis of individual CNS structures was performed.
Dosimetric and toxicity data were available for 67 patients (27 CRT, 40 IMRT). Retrospective delineation of the posterior fossa, brainstem, cerebellum, pituitary gland, pineal gland, hypothalamus, hippocampus and basal ganglia was performed. Dosimetry was reviewed using summary statistics and dose-volume atlases.
A statistically significant increase in maximum and mean doses to each structure was observed for patients who received IMRT compared to those who received CRT. Both maximum and mean doses were significantly higher for the posterior fossa, brainstem and cerebellum for the 42 patients who reported acute fatigue of Grade 2 or higher (p ≤ 0.01) compared to the 25 who did not. Dose-volume atlases of the same structures indicated that regions representing larger volumes and higher doses to each structure were consistent with a higher incidence of acute fatigue. There was no association between the dose distribution and acute fatigue for the other structures tested.
The excess fatigue reported in the IMRT arm of the trial may, at least in part, be attributed to the dose distribution to the posterior fossa, cerebellum and brainstem. Future studies that modify dose delivery to these structures may allow us to test the hypothesis that radiation-induced fatigue is avoidable.
PARSPORT（ISRCTN48243537，CRUK/03/005）的 III 期腮腺保留放疗试验出现了一个意外发现，与标准常规放疗（CRT）相比，接受调强放疗（IMRT）的患者出现了明显的急性疲劳增加。一个可能的解释是由于射束门的不同，导致中枢神经系统（CNS）结构的剂量不同。利用试验数据，对单个 CNS 结构进行了剂量学分析。
67 例患者（27 例 CRT，40 例 IMRT）的剂量学和毒性数据可用。对后颅窝、脑干、小脑、垂体、松果体、下丘脑、海马体和基底节进行了回顾性勾画。使用汇总统计数据和剂量-体积图谱对剂量进行了审查。
与 CRT 组相比，接受 IMRT 的患者每个结构的最大和平均剂量均显著增加。42 例报告 2 级或以上急性疲劳的患者（p≤0.01）的后颅窝、脑干和小脑的最大和平均剂量均显著高于 25 例未报告的患者。相同结构的剂量-体积图谱表明，代表每个结构更大体积和更高剂量的区域与更高的急性疲劳发生率一致。对于其他测试的结构，剂量分布与急性疲劳之间没有关联。
试验中 IMRT 组报告的额外疲劳可能至少部分归因于后颅窝、小脑和脑干的剂量分布。未来可能会修改这些结构的剂量分布，以验证辐射诱导性疲劳是否可以避免。
