Albertini Francesca, Bolsi Alessandra, Lomax Antony J, Rutz Hans Peter, Timmerman Beate, Goitein Gudrun
Center for Proton Radiation Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.
Radiother Oncol. 2008 Feb;86(2):187-94. doi: 10.1016/j.radonc.2007.11.032. Epub 2008 Jan 15.
A retrospective study to investigate the sensitivity of intensity modulated proton therapy (IMPT) to changes in body weight occurring during the course of radiotherapy for patients treated in the sacral region.
During therapy, important weight gain and loss were observed for two patients treated to para-spinal tumors, which resulted in both patients being re-scanned and re-planned. Both patients were treated as part of their therapy, with a narrow-angle IMPT (NA-IMPT) plan delivering a 'dose hole' around the cauda equina (CE), which was mainly formed through modulation of Bragg peaks in depth. To investigate the impact of these weight changes on the proton range and delivered dose, the nominal fields were re-calculated on the new CT data sets. Results were analyzed by comparing these new plans with those originally delivered and by calculating changes in range and delivered doses in target volumes and normal tissues.
Maximum differences in proton range in the CE region of up to +8 mm and -13 mm, respectively, for the patient who gained weight and for the patient who lost weight, increased the maximum dose to the CE by only 2%. This indicates that both IMPT plans were relatively insensitive to substantial range uncertainties. Even greater differences in range (16 mm) in the planning target volume only slightly affected its dose homogeneity (differences in V(90%) of 6% in the worst case). Nevertheless, some large undesired local dose differences were observed.
We demonstrated, that, at least for the two analyzed cases, NA-IMPT plans are less sensitive to weight variations than one may expect. Still, we would advise to calculate new plans in case of substantial change in weight for patients treated in the sacral region, primarily due to the presence of new hot/cold area.
进行一项回顾性研究，以调查调强质子治疗（IMPT）对骶骨区域放疗过程中患者体重变化的敏感性。
在治疗过程中，观察到两名接受脊柱旁肿瘤治疗的患者体重显著增加和减轻，这导致两名患者都进行了重新扫描和重新计划。两名患者均作为其治疗的一部分，采用窄角IMPT（NA-IMPT）计划，该计划在马尾神经（CE）周围形成一个“剂量孔”，主要通过深度上的布拉格峰调制形成。为了研究这些体重变化对质子射程和 delivered dose的影响，在新的CT数据集上重新计算了标称射野。通过将这些新计划与最初实施的计划进行比较，并计算靶区和正常组织中射程和 delivered doses的变化来分析结果。
体重增加的患者和体重减轻的患者在CE区域的质子射程最大差异分别高达+8毫米和-13毫米，这仅使CE的最大剂量增加了2%。这表明两个IMPT计划对较大的射程不确定性相对不敏感。计划靶区内更大的射程差异（16毫米）仅对其剂量均匀性有轻微影响（最坏情况下V(90%)的差异为6%）。然而，观察到一些较大的不期望的局部剂量差异。
我们证明，至少对于所分析的两个病例，NA-IMPT计划对体重变化的敏感性低于预期。尽管如此，我们建议对于骶骨区域接受治疗的患者，若体重发生显著变化，应重新计算新计划，主要是因为出现了新的热点/冷点区域。
