Fager Marcus, Gubanski Michael, Carlsson Tedgren Åsa, Benmakhlouf Hamza
Department of Oncology-Pathology, Karolinska Institutet, Solna, Sweden; Department of Nuclear Medicine and Medical Physics, Karolinska University Hospital, Solna, Sweden.
Department of Oncology-Pathology, Karolinska Institutet, Solna, Sweden; Department of Radiotherapy, Karolinska University Hospital, Solna, Sweden; Department of Neurosurgery, Karolinska University Hospital, Solna, Sweden.
Acta Oncol. 2025 Feb 26;64:319-325. doi: 10.2340/1651-226X.2025.41924.
Majority of vestibular schwannoma (VS) patients have undergone gamma-knife radiosurgery (GKRS) with favorable results. Clinical evidence is derived from doses calculated with a type-a algorithm, which in this case assumes all material to be water. A type-b algorithm (Convolution algorithm [CA]) taking tissue heterogeneity into account is available. Historically, body contour is defined using a 16-point approximation, whereas modern softwares generate the body from Magnetic Resonance Imaging (MRI). The accuracy in dose-calculation algorithms (DCA) and contouring method (CM) will have a significant influence in the relation between clinical outcome and dosimetric data. The objective was to investigate the impact of DCA and CMs on dose distribution while preserving treatment conditions.
Treatment plans for 16 VS patients were recalculated in terms of DCA and CM. The difference in the dose covering 99% of the VS (DVS99%) depending on CM and DCA was estimated. The difference in DVS99% was used to adopt the prescription of new CA-based plans. CA-plans were recalculated to TMR10 to evaluate clinical treatability, as clinical evidence is derived from TMR10-doses.
Both CM and DCA had a significant impact on the dose to VS and surrounding structures. CM altered the doses homogenously by 2.1-3.3%, whereas DCA heterogeneously by 5.0-10.7%. An increase of 9.1[8.1, 10.0]% was found for DVS99% and the CA-plans recalculated into TMR10 resulted in clinically treatable plans.
We conclude that transferring to more modern algorithms that take tissue heterogeneity into account heterogeneously alter dose distributions. This work establishes a safe pathway to adopt prescription dose for VS while preserving clinical treatability.
大多数前庭神经鞘瘤（VS）患者已接受伽玛刀放射外科治疗（GKRS），效果良好。临床证据来自于使用A型算法计算的剂量，在这种情况下，该算法假定所有物质均为水。有一种考虑组织异质性的B型算法（卷积算法[CA]）。从历史上看，身体轮廓是使用16点近似法定义的，而现代软件则根据磁共振成像（MRI）生成身体轮廓。剂量计算算法（DCA）和轮廓描绘方法（CM）的准确性将对临床结果与剂量数据之间的关系产生重大影响。目的是在保持治疗条件的同时，研究DCA和CM对剂量分布的影响。
根据DCA和CM重新计算16例VS患者的治疗计划。估计了根据CM和DCA覆盖99%VS的剂量（DVS99%）的差异。DVS99%的差异用于采用基于新CA的计划的处方。将基于CA的计划重新计算为TMR10，以评估临床可治疗性，因为临床证据来自TMR10剂量。
CM和DCA对VS和周围结构的剂量均有显著影响。CM使剂量均匀改变2.1-3.3%，而DCA使剂量不均匀改变5.0-10.7%。发现DVS99%增加了9.1[8.1, 10.0]%，重新计算为TMR10的基于CA的计划产生了临床可治疗的计划。
我们得出结论认为，转向考虑组织异质性的更现代算法会不均匀地改变剂量分布。这项工作建立了一条在保持临床可治疗性的同时采用VS处方剂量的安全途径。
