Prasartseree Tissana, Dankulchai Pittaya, Hoskin Peter J
Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Mount Vernon Cancer Centre, Northwood, United Kingdom.
J Contemp Brachytherapy. 2020 Oct;12(5):441-453. doi: 10.5114/jcb.2020.100377. Epub 2020 Oct 30.
In this paper, excess dose is originally proposed to represent the dose outside the target volume that encompass only organs at risk (OARs), not the whole dose volume of isodose surface volume (ISV). By means of spatial consideration, excess dose-related parameters would also compensate inconsistent applicator positions and OARs motion, which may deviate the identical dose small-volume assumption of D. Late toxicity correlations of these parameters were investigated.
A retrospective review was performed on cervical cancer high-dose-rate image-guided adaptive brachytherapy (HDR-IGABT). From ISVs of 60 to 100 Gy EQD (a/β = 3), excess dose-related parameters were derived as following: toxicity negligible volume (Vneg = V of toxicity negligible organs; high-risk clinical target volume - HR-CTV, uterus, and vagina), excess dose volume (Vex = ISV - Vneg), Vneg normalized parameters of excess dose volume ratio (Rex = Vex/Vneg), and indirect excess dose volume ratio (iRex = ISV/Vneg). Relationships between toxicity and these parameters were analyzed using a mean difference and a probit analysis method. Net reclassification indices (NRIs) were used to compare iRex60 and D gastrointestinal (GI) toxicity prediction.
From 143 cases with an incidence of 34.9% and 10.5% of 3-year grade 2-4 GI and genitourinary (GU) toxicity, respectively, comparisons of means showed significant difference between grade 0-1 and 2-4 toxicities for late GI toxicity for all parameters, except ISV. There was a dose-response relationship with toxicity for each parameter across the range of 60-100 Gy EQD. ED of iRex60 and iRex70 were 2.1 and 1.2, respectively. By comparing iRex60 and D, additive and absolute NRIs were +6.45 and +7.69%, respectively. The reclassification significantly occurred in range of 65-75 Gy of rectum D.
Excess dose-related parameters, including Vex, Rex, and iRex, showed significant mean differences and parameter-toxicity relationships for late GI but not for GU toxicities. Positive NRIs suggest iRex60 utilization for spatial control of dose expansion, in addition to high-dose control with OAR small volumes. Further investigations are needed to define the optimum use of these predictors.
在本文中，最初提出用过量剂量来表示靶体积之外仅包含危及器官（OARs）的剂量，而非等剂量曲面体积（ISV）的整个剂量体积。通过空间考量，与过量剂量相关的参数也将补偿施源器位置不一致和OARs运动的影响，这可能会偏离D的相同剂量小体积假设。研究了这些参数与晚期毒性的相关性。
对宫颈癌高剂量率图像引导自适应近距离放疗（HDR-IGABT）进行回顾性研究。从60至100 Gy EQD（α/β = 3）的ISV中，得出与过量剂量相关的参数如下：毒性可忽略体积（Vneg = 毒性可忽略器官的体积；高危临床靶体积 - HR-CTV、子宫和阴道）、过量剂量体积（Vex = ISV - Vneg）、过量剂量体积比的Vneg归一化参数（Rex = Vex/Vneg）以及间接过量剂量体积比（iRex = ISV/Vneg）。使用均值差异和概率分析方法分析毒性与这些参数之间的关系。使用净重新分类指数（NRIs）比较iRex60和D对胃肠道（GI）毒性的预测。
在143例病例中，3年2 - 4级GI毒性和泌尿生殖系统（GU）毒性的发生率分别为34.9%和10.5%，均值比较显示，除ISV外，所有参数在0 - 1级和2 - 4级晚期GI毒性之间存在显著差异。在60 - 100 Gy EQD范围内，每个参数与毒性均存在剂量反应关系。iRex60和iRex70的ED分别为2.1和1.2。通过比较iRex60和D，相加和绝对NRIs分别为 +6.45%和 +7.69%。重新分类显著发生在直肠D为65 - 75 Gy的范围内。
与过量剂量相关的参数，包括Vex、Rex和iRex，在晚期GI毒性方面显示出显著的均值差异和参数 - 毒性关系，但在GU毒性方面未显示。阳性NRIs表明，除了通过OAR小体积进行高剂量控制外，iRex60还可用于剂量扩展的空间控制。需要进一步研究以确定这些预测指标的最佳用途。
