Ferrer Carlos, Huertas Concepción, Ocanto Abrahams, García David, Plaza Rodrigo, Mínguez Cristina, de la Monja Patricia, Escribano Anne, Pérez Antonio, Sáez Moisés
Medical Physics and Radiation Protection Department, H.U. La Paz, Madrid, Spain.
Radiation Oncology Department, H.U. La Paz, Madrid, Spain.
Rep Pract Oncol Radiother. 2024 Feb 16;28(6):772-783. doi: 10.5603/rpor.98734. eCollection 2023.
Total lymphoid irradiation (TLI) is a conditioning regimen in allogeneic hematopoietic stem cell transplantation (allo-HSCT) which may reduce long-term toxicities attributed to other techniques, such as total body irradiation (TBI). At our institution, TLI treatments were first planned with the three-dimensional conformal radiation therapy (3D-CRT) technique and later with volumetric modulated arc therapy (VMAT). With the recent availability of a basic helical tomotherapy (HT), the possible dosimetric gain of the latter for TLI is studied.
22 pediatric patients were planned for VMAT and HT, prescribed to 8 Gy in 4 fractions. VMAT was planned with template based on a single cost function, using the Monaco treatment planning system (TPS). HT plans were planned using Accuray Precision TPS for a basic HT without the dynamic jaws feature or VOLO-Ultra algorithm. Plan quality was analyzed based on four quality indices, mean and maximum doses to planning target volume (PTV) and organs at risk (OARs), dose gradient and integral doses. Differences were analyzed with Wilcoxon signed-rank test.
HT plans resulted in improved conformity (CI) and homogeneity indices (HI) (p < 0.05) but less steep dose gradient (p = 0.181). VMAT plans created larger areas with high doses within the PTV, while comparable doses to OARs, except mainly for the spinal marrow, for which a reduction of 37.7% in D was obtained (p < 0.05). Integral dose for non-tumor tissue was 11.3% lower with the VMAT template (p < 0.05).
HT achieves better conformity and homogeneity even without its more advanced features. Nevertheless, the VMAT template achieves dosimetric results close to those of HT, both with similar clinical outcome.
全身淋巴照射（TLI）是异基因造血干细胞移植（allo-HSCT）中的一种预处理方案，它可能会降低因其他技术（如全身照射（TBI））导致的长期毒性。在我们机构，TLI治疗最初采用三维适形放疗（3D-CRT）技术进行规划，后来采用容积调强弧形放疗（VMAT）。随着近期基本螺旋断层放疗（HT）的出现，研究了后者在TLI方面可能的剂量学优势。
计划对22例儿科患者进行VMAT和HT治疗，处方剂量为8 Gy，分4次给予。VMAT计划使用基于单一成本函数的模板，采用Monaco治疗计划系统（TPS）进行规划。HT计划使用Accuray Precision TPS进行规划，用于基本的HT，不具备动态准直器功能或VOLO-Ultra算法。基于四个质量指标分析计划质量，即计划靶体积（PTV）和危及器官（OARs）的平均剂量和最大剂量、剂量梯度和积分剂量。采用Wilcoxon符号秩检验分析差异。
HT计划导致适形指数（CI）和均匀性指数（HI）得到改善（p < 0.05），但剂量梯度较缓（p = 0.181）。VMAT计划在PTV内产生了更大的高剂量区域，而对OARs的剂量相当，除了脊髓，其剂量降低了37.7%（p < 0.05）。VMAT模板的非肿瘤组织积分剂量低11.3%（p < 0.05）。
即使没有更先进的功能，HT也能实现更好的适形性和均匀性。然而，VMAT模板在剂量学结果上与HT接近，两者临床结果相似。
