局限期小细胞肺癌全脑预防照射保护海马回区的初步临床研究

Primary clinical study of hippocampal-sparing prophylactic cranial irradiation in limited-stage small-cell lung cancer

目的 初步观察局限期SCLC化放疗后HT的PCI对海马回区保护照射后的临床反应,并与IMRT、VMAT计划剂量分布进行比较.方法 2014年4-6月,6例局限期SCLC化放疗后达CR患者1个月内脑核磁排除脑转移后接受保护海马回区HT的PCI.将CT定位图像与脑核磁图像进行融合,在融合图像上勾画出海马回,外扩3 mm边界形成减量区域.HT、IMRT、VMAT处方剂量均为95％PTV 25 Gy分10次.评价HT的临床疗效、不良反应、认知功能及脑转移情况,比较3种计划靶区、海马回区剂量分布.结果 观察期内l例腹壁及腹腔淋巴结转移、1例局部复发,无脑转移.1＋2级头痛、头晕、脱发反应分别为3＋1、3＋1、4＋2例,复诊MMSE平均得分与疗前相近（29.2、29.3、29.7分,P=0.083、0.317、0.157）.IMRT、VMAT计划的海马回区Dmean分别为16.85、17.59Gy.HT计划可将海马回区Dmean降至5.26 Gy、外扩减量区降至6.21Gy,处方剂量分别比IMRT、VMAT的降低79％、71％.HT平均处方剂量覆盖率为94.48％.结论 应用HT保护海马回区PCI达到了理想剂量分布及较好靶区覆盖度,患者不良反应未增加,认知功能变化尚需延长观察时间及扩大病例进一步研究.

Objective To preliminarily observe the clinical efficacy of hippocampal-sparing prophylactic cranial irradiation （HS-PCI） using helical tomotherapy （HT） in patients with limited-stage small-cell lung cancer （LS-SCLC） after chemoradiotherapy,and compare HT with intensity-modulated radiotherapy （IMRT） and volumetric modulated arc therapy （VMAT） in dose distribution.Methods From April to June,2014,six patients with LS-SCLC who had achieved a complete remission after chemoradiotherapy were assigned to HS-PCI using HT within a month after brain metastasis was ruled out using brain magnetic resonance imaging （MRI）.After fusing CT images and MRI images,the hippocampus was contoured in the fusion images and hippocampal avoidance regions were created using a volumetric expansion of 3 mm around the hippocampus.A dose of 25 Gy in 10 fractions to 95% of planning target volume （PTV） was prescribed in HT,IMRT,and VMAT.The clinical efficacy,adverse reactions,neurocognitive function,and brain metastasis were evaluated for HT.The dose distribution in PTV and hippocampus were compared between HT,IMRT,and VMAT.Results There were one patient with abdominal wall and abdominal lymph node metastases,one patient with local recurrence,and no patient with brain metastasis during the observation period.The numbers of patients with grade 1 and grade 2 headache,dizziness,and hair loss reactions were 3 and 1,3 and 1,and 4 and 2,respectively.There were no significant differences in the average score of the Mini-Mental State Examination before treatment and at 3 and 6 months after treatment （29.7,29.2,and 29.3 ; P =0.083,0.317,and 0.157）.The mean dose to the hippocampus was 16.85 Gy for IMRT and 17.59 Gy for VMAT.For HT,the mean doses to the hippocampus and avoidance regions were reduced to 5.26 Gy and 6.21 Gy,respectively.The prescribed dose for HT was reduced by 79% and 71% compared with IMRT and VMAT,respectively.The average coverage rate of the prescribed dose was 94.48% for HT.Conclusions HT achieves promising dose distribution and target coverage in sparing of the hippocampus.Moreover,HT dose not increase the incidence of adverse reactions.The change in neurocognitive function needs to be further studied with longterm observation and large-scale sampling.