Prostate cancer external beam radiation therapy can result in toxicity due to organ at risk (OAR) dose, potentially impairing quality of life. A polyethylene glycol‐based spacer, SpaceOAR© hydrogel (SOH), implanted between prostate gland and rectum may significantly reduce dose received by the rectum and hence risk of rectal toxicity. SOH implant is not equally effective in all patients. Determining patients in which the implant will offer most benefit, in terms of rectal dose reduction, allows for effective management of SOH resources. Several factors have been shown to be correlated with reduction in rectal dose including distance between rectum and planning treatment volume (PTV), volume of rectum in the PTV, and change in rectum volume pre‐ to post‐SOH. Several of these factors along with other pre‐SOH CT metrics were able to predict reduction in rectal dose associated with SOH implant. Rectal V55Gy metric, was selected as the dose level of interest in the context of 60 Gy in 20 fraction treatment plans. Models were produced to predict change in RV55Gy and pre‐SOH hydrogel RV55Gy. These models offered R‐squared between 0.81 and 0.88 with statistical significance in each model. Applying an  = 3% lower limit of pre‐SOH RV55 Gy and an  = 3.5% lower limit on change in RV55 Gy, retained 60% of patients experiencing the largest rectal dose reduction from the hydrogel. This may offer a clinically useful tool in deciding which patients should receive SOH implant given limited resources. Predictive models, nomograms, and a workflow diagram were produced for clinical management of SOH implant.

中文翻译：

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SpaceOAR©水凝胶直肠剂量减少预测模型：决策支持工具。

由于高危器官（OAR）剂量，前列腺癌的外部束放射疗法可能导致毒性，从而潜在地损害生活质量。植入前列腺和直肠之间的基于聚乙二醇的垫片SpaceOAR©水凝胶（SOH）可能会显着减少直肠接受的剂量，从而降低直肠毒性的风险。SOH植入物并非对所有患者均有效。在减少直肠剂量方面，确定将为植入物提供最大益处的患者，可以有效管理SOH资源。已显示出与直肠剂量减少相关的几个因素，包括直肠与计划治疗量（PTV）之间的距离，PTV中的直肠量以及SOH前后直肠体积的变化。其中一些因素以及其他SOH之前的CT指标能够预测与SOH植入物相关的直肠剂量的减少。直肠V55Gy指标在20个治疗方案中选择60 Gy作为目标剂量水平。产生模型以预测RV55Gy和SOH前水凝胶RV55Gy的变化。这些模型的R平方在0.81和0.88之间，每个模型具有统计学意义。应用 = SOH前RV55 Gy的下限降低3％，RV55 Gy的 变化下限= 3.5％，保留了60％经历水凝胶直肠最大剂量减少的患者。在资源有限的情况下，这可以为确定哪些患者应接受SOH植入物提供临床上有用的工具。产生了用于SOH植入物临床管理的预测模型，列线图和工作流程图。