高分级脑胶质瘤同步加量调强放射治疗的疗效与剂量分析

The efficacy and dose analysis of SIB-IMRT for high grade cerebral glioma

目的评价高分级脑胶质瘤应用同步加量调强放疗(SIB-IMRT)的临床疗效、毒性和剂量的可行性。方法 2009年11月至2012年12月入选16例高分级(Ⅲ～Ⅳ级)脑胶质瘤患者。调强放疗定义两个计划靶区(PTV):大体肿瘤靶区(GTV)包及T1加权增强期外放0.5 cm定义为计划肿瘤靶区(PGTV),放射剂量70 Gy/28次,2.5 Gy/次;亚临床区(CTV)为GTV外扩2 cm(包及T2水肿区)外放0.5 cm为计划亚临床靶区(PCTV),放射剂量56 Gy/28次,2.0 Gy/次。用剂量体积直方图分析靶区和危险器官剂量分布,并评价疗效、毒性、分割及总剂量的可行性。结果中位随访时间17个月,截止随访日期所有患者肿瘤均出现复发,15例(93.8%)出现靶区内复发,其中12例患者出现PGTV复发和3例在PCTV的复发;1例在靶区外复发。4例患者随访截止日仍存活,其余12例患者因肿瘤进展死亡。总的1年无进展生存(PFS)为20%,2年PFS为10%;1年和2年总生存(OS)率分别为77%和31%。治疗过程中6例患者发生Ⅰ～Ⅱ级急性放射毒性反应,无相关的放射晚期毒性反应。结论 SIB-IMRT未能改善高分级脑胶质瘤的局部控制率和生存率,但可以给肿瘤区和周围水肿区不同剂量照射,在肿瘤区及周边组织形成剂量梯度,降低正常脑组织受量。

Objective To assess the clinical outcomes, toxicities and dosimetric feasibility of simultaneous integrated boost intensity modulated radiotherapy （SIB-IMRT） in high grade glioma. Methods Sixteen patients with Ⅲ-Ⅳ grade malignant gliomas treated between November 2009 and December 2012 were enrolled in this study. Two planning target volumes were defined：the planning gross target volume （PGTV） was defined as 0. 5 cm beyond the gross target volume （ GTV）, and planning sub-clinical target volume （PCTV） was defined as 0.5 cm beyond GTV outward 2.0 cm. The doses of 70 Gy/28 fractions （fr） and 2.5 Gy/fr were administered in PGTV,and 56 Gy/28 fr and 2.5 Gy/fr were administered in PCTV. The dose distributions of target volume and risk organs were analyzed, and the efficacy,toxicity and dosimetric feasibility were assessed. Results Up to the end of follow-up （median followed time：17 months）, all of the patients experienced tumor recurrence. Fifteen cases （93.8 % ） were recurrence in target volume in whom 12 were seen in PGTV and 3 seen in PCTV ,and one case was recurrence outside the target volume. Of 16 cases of recurrence,4 remained to survival up to the end of follow-up, and the other died of tumor progression. Total progression-free survival（PFS） rate was 20% , and 2-year PFS rate was 10%. The 1-year and 2- year overall survival rates were 77% and 31%, respectively. The acute Ⅰ-Ⅱ grade radiotoxicity effects in the treatment were seen in 6 cases, and no radiotherapy-related toxicity effects in late treatment period occurred. Conclusions Though SIB-IMRT does not improve local control rate and survival rate of cerebral glioma, it can decrease received radio-dose of normal cerebral tissues due to delivering different doses to tumor and surrounding edema regions and thus forming dose-gradient.