Nkiwane Karen S, Pötter Richard, Tanderup Kari, Federico Mario, Lindegaard Jacob C, Kirisits Christian
Department of Radiotherapy, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
Brachytherapy. 2013 Jul-Aug;12(4):317-23. doi: 10.1016/j.brachy.2012.11.001. Epub 2013 Mar 7.
Three-dimensional evaluation and comparison of target and organs at risk (OARs) doses from two traditional standard source loading patterns in the frame of MRI-guided cervical cancer brachytherapy for various clinical scenarios based on patient data collected in a multicenter trial setting.
Two nonoptimized three-dimensional MRI-based treatment plans, Plan 1 (tandem and vaginal loading) and Plan 2 (tandem loading only), were generated for 134 patients from seven centers participating in the EMBRACE study. Both plans were normalized to point A (Pt. A). Target and OAR doses were evaluated in terms of minimum dose to 90% of the high-risk clinical target volume (HRCTV D90) grouped by tumor stage and minimum dose to the most exposed 2cm³ of the OARs volume.
An HRCTV D90 ≥ Pt. A was achieved in 82% and 44% of the patients with Plans 1 and 2, respectively. Median HRCTV D90 with Plans 1 and 2 was 120% and 90% of Pt. A dose, respectively. Both plans had optimal dose coverage in 88% of Stage IB tumors; however, the tandem-only plan resulted in about 50% of dose reduction to the vagina and rectum. For Stages IIB and IIIB, Plan 1 had on average 35% better target coverage but with significant doses to OARs.
Standard tandem loading alone results in good target coverage in most Stage IB tumors without violating OAR dose constraints. For Stage IIB tumors, standard vaginal loading improves the therapeutic window, however needs optimization to fulfill the dose prescription for target and OAR. In Stage IIIB, even optimized vaginal loading often does not fulfill the needs for dose prescription. The significant dose variation across various clinical scenarios for both target and OARs indicates the need for image-guided brachytherapy for optimal dose adaptation both for limited and advanced diseases.
基于多中心试验收集的患者数据，在MRI引导的宫颈癌近距离放疗框架下，对两种传统标准源加载模式下的靶区和危及器官（OARs）剂量进行三维评估和比较，以适用于各种临床场景。
为参与EMBRACE研究的七个中心的134例患者生成了两个非优化的基于MRI的三维治疗计划，计划1（串联和阴道加载）和计划2（仅串联加载）。两个计划均归一化至A点（Pt. A）。根据肿瘤分期，通过高危临床靶区体积（HRCTV）90%的最小剂量以及OARs体积中最暴露的2cm³的最小剂量来评估靶区和OARs剂量。
计划1和计划2分别在82%和44%的患者中实现了HRCTV D90≥Pt. A。计划1和计划2的HRCTV D90中位数分别为Pt. A剂量的120%和90%。两个计划在88%的IB期肿瘤中具有最佳剂量覆盖；然而，仅串联计划使阴道和直肠的剂量降低了约50%。对于IIB期和IIIB期，计划1的靶区覆盖平均好35%，但对OARs有显著剂量。
单独的标准串联加载在大多数IB期肿瘤中可实现良好的靶区覆盖，而不违反OARs剂量限制。对于IIB期肿瘤，标准阴道加载改善了治疗窗口，但需要优化以满足靶区和OARs的剂量处方。在IIIB期，即使是优化的阴道加载也常常无法满足剂量处方的需求。靶区和OARs在各种临床场景中的显著剂量差异表明，对于局限性和晚期疾病，需要图像引导的近距离放疗来实现最佳剂量适配。
