Offline adaptive radiotherapy for hypofractionated prostate therapy

The study was conducted retrospectively at the Radiation Oncology, Steve Biko Academic Hospital. Data from 30 patients who underwent localised prostate cancer treatment were analysed, with a primary focus on the CBCT images obtained after applying treatment couch shifts to verify the treatment setup. These CBCT images were used to create new plans, which were then compared to reference plans based on the initial CT images. The 3-dimensional couch shift coordinates were evaluated against different absorbed dose constraints on the Planning Target Volume (PTV), specifically D2% (maximum absorbed dose) and D99%≥57 Gy (minimum absorbed dose). After applying couch shifts, the average results showed no significant difference between the planned and treated absorbed doses for D98% (F = 1.570, p = 0.201 > 0.05) and D2% (F = 1.841, p = 0.135 > 0.05). However, linear regression analysis revealed that inferior couch shifts significantly predicted D98% during treatment, while superior (SUP) couch shifts significantly predicted D2% during treatment. Notably, each unit of superior couch shift led to a 1.797 Gy decrease in D2% during treatment (t = -3.036, p < 0.05), with a negative beta value (β = -1.797). Despite these findings, the overall dose to the PTV did not significantly differ from the planning objectives. The differences in mean shifts and dosimetric plans/re-plans were compared using the ANOVA analysis.

本研究于Steve Biko学术医院放射肿瘤科进行回顾性分析。对接受局限性前列腺癌治疗的30名患者的数据进行了分析，主要关注在应用治疗床位移后获取的CBCT图像，以验证治疗装置的设置。这些CBCT图像被用于创建新的治疗计划，随后与基于初始CT图像的参考计划进行比较。对三维治疗床位移坐标进行了评估，以应对计划靶区（PTV）上的不同吸收剂量限制，具体为D2%（最大吸收剂量）和D99%≥57 Gy（最小吸收剂量）。在应用治疗床位移后，平均结果显示，对于D98%（F = 1.570，p = 0.201 > 0.05）和D2%（F = 1.841，p = 0.135 > 0.05），计划吸收剂量与治疗吸收剂量之间无显著差异。然而，线性回归分析表明，下位治疗床位移显著预测了治疗过程中的D98%，而上位（SUP）治疗床位移则显著预测了治疗过程中的D2%。值得注意的是，每次上位治疗床位移单位的变化导致治疗过程中D2%降低了1.797 Gy（t = -3.036，p < 0.05），具有负的回归系数（β = -1.797）。尽管有这些发现，PTV的整体剂量与计划目标并无显著差异。通过方差分析（ANOVA）比较了平均位移和剂量学计划/重新计划的差异。