Nepean Cancer Care Centre, Nepean Hospital, Kingswood, New South Wales, 2747, Australia.
Nepean Cancer Care Centre, Nepean Hospital, Kingswood, New South Wales, 2747, Australia.
Med Dosim. 2021;46(3):269-273. doi: 10.1016/j.meddos.2021.02.005. Epub 2021 Mar 13.
Generic dose-volume constraints of the rectum/bladder (R/B) are used in inverse planning to reduce doses to these organs for patients undergoing prostate radiotherapy. A retrospective study was undertaken to assess correlations between the overlap of the R/B with the planning target volume (PTV) and the dose received during planning to organs at risk (OARs). Data for 105 prostate cancer patients who had volumetric modulated arc therapy (VMAT) to the intact prostate and proximal seminal vesicles at Nepean Cancer Care Centre from 2011 to 2015 were analyzed. R/B volume, R/B-PTV overlap volume, and R/B-PTV overlap percent metrics were collected with VMAT planning objectives. Characteristics were evaluated for correlation with different planning outcomes. The percentage overlap between the R/B and PTV were highly correlated to the doses to the relevant OAR, with a coefficient of determination (R) of 0.63 for the rectum volume percentage receiving more than 75 Gy (RV) and R of 0.91 for the bladder volume percentage receiving more than 70 Gy (BV). We identified a cut-off value of 10.14% (sensitivity 84.62%, specificity 80.43%) as predictive of RV < 10% and a cut-off of 7.95% (sensitivity 97.62%, specificity 92.06%) as predictive of BV < 15%. A 95% prediction interval assisted in identifying individualized R/B planning goals. The R/B-PTV percentage overlap has a high reliability in estimating sparing of the R/B. This prediction model can be used to improve planning efficiency and create customised automated OAR planning goals in prostate VMAT plans. By doing this, the radiation doses received by these OARs can be minimized.
在进行前列腺放射治疗时，通常使用直肠/膀胱（R/B）的通用剂量-体积限制来降低这些器官的剂量。本研究回顾性评估了 R/B 与计划靶区（PTV）重叠程度与计划危及器官（OAR）剂量之间的相关性。对 2011 年至 2015 年期间在 Nepean Cancer Care Centre 接受完整前列腺和近端精囊容积调强弧形治疗（VMAT）的 105 例前列腺癌患者的数据进行了分析。使用 VMAT 计划目标收集了 R/B 体积、R/B-PTV 重叠体积和 R/B-PTV 重叠百分比指标。评估了这些特征与不同计划结果之间的相关性。R/B 与 PTV 之间的重叠百分比与相关 OAR 的剂量高度相关，直肠体积百分比（RV）接受超过 75Gy 的决定系数（R）为 0.63，膀胱体积百分比（BV）接受超过 70Gy 的 R 为 0.91。我们确定了 10.14%（敏感性 84.62%，特异性 80.43%）作为 RV<10%的预测值，7.95%（敏感性 97.62%，特异性 92.06%）作为 BV<15%的预测值。95%预测区间有助于确定个体化 R/B 计划目标。R/B-PTV 百分比重叠度在估计 R/B 保护方面具有很高的可靠性。该预测模型可用于提高计划效率并为前列腺 VMAT 计划创建定制的自动化 OAR 计划目标。通过这样做，可以最大限度地减少这些 OAR 接收到的辐射剂量。
