Merchant Thomas E, Hua Chia-Ho, Shukla Hemant, Ying Xiaofei, Nill Simeon, Oelfke Uwe
Division of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Pediatr Blood Cancer. 2008 Jul;51(1):110-7. doi: 10.1002/pbc.21530.
To determine whether proton radiotherapy has clinical advantages over photon radiotherapy, we modeled the dose characteristics of both to critical normal tissue volumes using data from patients with four types of childhood brain tumors.
Three-dimensional imaging and treatment planning data, including targeted tumor and normal tissues contours, were acquired for 40 patients, 10 each with optic pathway glioma (OPG), craniopharyngioma (CR), infratentorial ependymoma (EP), or medulloblastoma (MB). Dose-volume data were collected for the entire brain, temporal lobes, cochlea, and hypothalamus from each patient. The data were averaged and compared based on treatment modality (protons vs. photons) using dose-cognitive effects models. Outcomes were estimated over 5 years.
Relatively small critical normal tissue volumes such as the cochlea and hypothalamus may be spared from radiation exposure when not adjacent to the primary tumor volume. Larger normal tissue volumes such as the supratentorial brain or temporal lobes receive less of the low and intermediate doses. When applied to longitudinal models of radiation dose-cognitive effects, these differences resulted in clinically significant higher IQ scores for patients with MB and CR and academic reading scores in patients with OPG. Extreme differences between proton and photon dose distributions precluded meaningful comparison of protons and photons for patients with EP.
Differences in the overall dose distributions, as indicated by modeling changes in cognitive function, showed that a reduction in the lower-dose volumes or mean dose would have long-term, clinical advantages for children with MB, CR, and OPG.
为了确定质子放疗相对于光子放疗是否具有临床优势，我们利用四种儿童脑肿瘤患者的数据，对两种放疗方式在关键正常组织体积上的剂量特征进行了建模。
获取了40例患者的三维成像和治疗计划数据，包括靶向肿瘤和正常组织轮廓，其中10例患有视路胶质瘤（OPG）、颅咽管瘤（CR）、幕下室管膜瘤（EP）或髓母细胞瘤（MB）。收集每位患者全脑、颞叶、耳蜗和下丘脑的剂量体积数据。使用剂量认知效应模型，根据治疗方式（质子放疗与光子放疗）对数据进行平均和比较。评估5年期间的结果。
当与原发肿瘤体积不相邻时，相对较小的关键正常组织体积，如耳蜗和下丘脑，可能免受辐射暴露。较大的正常组织体积，如幕上脑或颞叶，接受的低剂量和中等剂量较少。当应用于辐射剂量认知效应的纵向模型时，这些差异导致MB和CR患者的智商得分在临床上显著更高，OPG患者的学术阅读得分更高。质子和光子剂量分布的极端差异使得无法对EP患者的质子和光子进行有意义的比较。
通过对认知功能变化进行建模表明，总体剂量分布的差异显示，降低低剂量体积或平均剂量对MB、CR和OPG儿童具有长期临床优势。
