Applying a proton beam in radiotherapy enables precise irradiation of the tumor volume, but only for continuous assessment of changes in patient anatomy. Proton beam range uncertainties in the treatment process may originate not only from physical beam properties but also from patient-specific factors such as tumor shrinkage, edema formation and sinus filling, which are not incorporated in tumor volume safety margins. In this paper, we evaluated variations in dose distribution in proton therapy resulting from the differences observed in the control tomographic images and the dosimetric influence of applied adaptive treatment. The data from weekly computed tomography (CT) control scans of 21 patients, which serve as the basis for adaptive radiotherapy, were used for this study. Dosimetric analysis of adaptive proton therapy (APT) was performed on patients with head and neck (H&N) area tumors who were divided into two groups: patients with tumors in the sinus/nasal area and patients with tumors in the brain area. For this analysis, the reference treatment plans were forward-calculated using weekly control CT scans. A comparative evaluation of organ at risk (OAR) dose-volume histogram (DVH) parameters, as well as conformity and homogeneity indices, was conducted between the initial and recalculated dose distributions to assess the necessity of the adaptation process in terms of dosimetric parameters. Changes in PTV volume after replanning were observed in seventeen patient cases, showing a discrepancy of over 1cm3in ten cases. In these cases, tumor progression occurred in 30% of patients, while regression was observed in 70%. The statistical analysis indicates that the use of the adaptive planning procedure results in a statistically significant improvement in dose distribution, particularly in the PTV area. The findings led to the conclusion that the adaptive procedure provides significant advantages in terms of dose distribution within the treated volume. However, when considering the entire patient group, APT did not result in a statistically significant dose reduction in OARs (α= 0.05).
在放射治疗中应用质子束可以实现对肿瘤体积的精确照射，但这仅适用于对患者解剖结构变化的持续评估。治疗过程中质子束射程的不确定性不仅源于物理束流特性，还可能来自患者特异性因素，如肿瘤缩小、水肿形成和窦腔填充，这些因素并未纳入肿瘤体积安全边界。本文评估了质子治疗中剂量分布的变化，这些变化源于控制断层图像中观察到的差异以及所应用的自适应治疗的剂量学影响。本研究使用了21例患者每周进行的计算机断层扫描（CT）控制扫描数据，这些数据作为自适应放射治疗的基础。对头颈部（H&N）区域肿瘤患者进行了自适应质子治疗（APT）的剂量学分析，这些患者被分为两组：窦/鼻区域肿瘤患者和脑部区域肿瘤患者。在此分析中，参考治疗计划使用每周的控制CT扫描进行前向计算。对初始剂量分布和重新计算的剂量分布之间的危及器官（OAR）剂量体积直方图（DVH）参数以及适形性和均匀性指数进行了比较评估，以从剂量学参数角度评估自适应过程的必要性。在17例患者中观察到重新计划后PTV体积的变化，其中10例患者的差异超过1立方厘米。在这些病例中，30%的患者出现肿瘤进展，而70%的患者观察到肿瘤消退。统计分析表明，使用自适应计划程序在剂量分布方面带来了统计学上的显著改善，特别是在PTV区域。研究结果得出结论，自适应程序在治疗体积内的剂量分布方面具有显著优势。然而，当考虑整个患者群体时，APT并未导致OARs的剂量在统计学上显著减少（α=0.05）。
肿瘤(癌症)患者之家