Dosimetric comparison of five different techniques for craniospinal irradiation across 15 European centers: analysis on behalf of the SIOP-E-BTG (radiotherapy working group)

Conventional techniques (3D-CRT) for craniospinal irradiation (CSI) are still widely used. Modern techniques (IMRT, VMAT, TomoTherapy^®, proton pencil beam scanning [PBS]) are applied in a limited number of centers. For a 14-year-old patient, we aimed to compare dose distributions of five CSI techniques applied across Europe and generated according to the participating institute protocols, therefore representing daily practice. A multicenter (<i>n</i> = 15) dosimetric analysis of five different techniques for CSI (3D-CRT, IMRT, VMAT, TomoTherapy^®, PBS; 3 centers per technique) was performed using the same patient data, set of delineations and dose prescription (36.0/1.8 Gy). Different treatment plans were optimized based on the same planning target volume margin. All participating institutes returned their best treatment plan applicable in clinic. The modern radiotherapy techniques investigated resulted in superior conformity/homogeneity-indices (CI/HI), particularly in the spinal part of the target (CI: 3D-CRT:0.3 vs. modern:0.6; HI: 3D-CRT:0.2 vs. modern:0.1), and demonstrated a decreased dose to the thyroid, heart, esophagus and pancreas. Dose reductions of &gt;10.0 Gy were observed with PBS compared to modern photon techniques for parotid glands, thyroid and pancreas. Following this technique, a wide range in dosimetry among centers using the same technique was observed (e.g., thyroid mean dose: VMAT: 5.6–24.6 Gy; PBS: 0.3–10.1 Gy). The investigated modern radiotherapy techniques demonstrate superior dosimetric results compared to 3D-CRT. The lowest mean dose for organs at risk is obtained with proton therapy. However, for a large number of organs ranges in mean doses were wide and overlapping between techniques making it difficult to recommend one radiotherapy technique over another.

用于全脑全脊髓照射（craniospinal irradiation, CSI）的常规技术（三维适形放射治疗，3D-CRT）目前仍被广泛应用。现代放射治疗技术（调强放射治疗IMRT、容积调强放射治疗VMAT、螺旋断层放射治疗TomoTherapy^®、质子笔形束扫描PBS）仅在少数医疗中心得到应用。本研究以1例14岁患者为对象，对欧洲各参与机构按照其临床规程开展的5种CSI技术的剂量分布进行对比分析，以反映日常临床实践的真实场景。本次多中心（n=15）剂量学分析涵盖5种CSI技术（3D-CRT、IMRT、VMAT、TomoTherapy^®、PBS），每种技术由3家中心独立完成，所有分析均采用同一患者的影像数据、靶区勾画方案及处方剂量（36.0/1.8 Gy）。所有治疗计划均基于统一的计划靶区边界开展优化，各参与机构均提交了其临床可用的最优治疗方案。研究结果显示，本次评估的现代放射治疗技术具有更优的适形度/均匀度指数（CI/HI），尤其在靶区脊髓段表现显著：三维适形放射治疗（3D-CRT）的CI为0.3，现代技术的CI为0.6；3D-CRT的HI为0.2，现代技术的HI为0.1。同时，现代技术可降低甲状腺、心脏、食管及胰腺的受照剂量。与现代光子技术相比，质子笔形束扫描（PBS）可使腮腺、甲状腺及胰腺的受照剂量降低10.0 Gy以上。此外，采用同一技术的不同中心间剂量学结果存在较大差异：例如容积调强放射治疗（VMAT）对应的甲状腺平均剂量为5.6~24.6 Gy，质子笔形束扫描（PBS）对应的甲状腺平均剂量为0.3~10.1 Gy。综上所述，相较于三维适形放射治疗（3D-CRT），本次研究所评估的现代放射治疗技术具有更优异的剂量学表现，其中质子治疗可使危及器官（organs at risk）获得最低的平均受照剂量。然而，多数危及器官的平均剂量范围跨度较大且不同技术间存在重叠，因此难以明确推荐某一种放射治疗技术优于其他技术。