文章：

优化碳离子放疗治疗大型盆腔肉瘤/脊索瘤中剂量平均线性能量转移分布的规划策略

Planning Strategy to Optimize the Dose-Averaged LET Distribution in Large Pelvic Sarcomas/Chordomas Treated with Carbon-Ion Radiotherapy

原文发布日期：9 October 2023

DOI: 10.3390/cancers15194903

类型: Article

开放获取: 是

英文摘要：

To improve outcomes in large sarcomas/chordomas treated with CIRT, there has been recent interest in LET optimization. We evaluated 22 pelvic sarcoma/chordoma patients treated with CIRT [large: HD-CTV ≥ 250 cm3(n = 9), small: HD-CTV < 250 cm3(n = 13)], DRBE|LEM-I= 73.6 (70.4–73.6) Gy (RBE)/16 fractions, using the local effect model-I (LEM-I) optimization and modified-microdosimetric kinetic model (mMKM) recomputation. We observed that to improve high-LETd distribution in large tumors, at least 27 cm3(low-LETd region) of HD-CTV should receive LETd of ≥33 keV/µm (p< 0.05). Hence, LETd optimization using ‘distal patching’ was explored in a treatment planning setting (not implemented clinically yet). Distal-patching structures were created to stop beams 1–2 cm beyond the HD-PTV-midplane. These plans were reoptimized and DRBE|LEM-I, DRBE|mMKM, and LETd were recomputed. Distal patching increased (a) LETd50% in HD-CTV (from 38 ± 3.4 keV/µm to 47 ± 8.1 keV/µm), (b) LETdmin in low-LETd regions of the HD-CTV (from 32 ± 2.3 keV/µm to 36.2 ± 3.6 keV/µm), (c) the GTV fraction receiving LETd of ≥50 keV/µm, (from <10% to >50%) and (d) the high-LETd component in the central region of the GTV, without significant compromise in DRBEdistribution. However, distal patching is sensitive to setup/range uncertainties, and efforts to ascertain robustness are underway, before routine clinical implementation.

摘要翻译： 

为改善经碳离子放射治疗（CIRT）的大型肉瘤/脊索瘤的疗效，近期对线性能量传输（LET）优化产生了研究兴趣。我们评估了22例接受CIRT治疗的盆腔肉瘤/脊索瘤患者[大型肿瘤：高危临床靶体积（HD-CTV）≥250 cm³（n=9）；小型肿瘤：HD-CTV <250 cm³（n=13）]，采用局部效应模型-I（LEM-I）优化方案，处方剂量为73.6（70.4–73.6）Gy（相对生物效应值）/16次分割，并通过修正微剂量动力学模型（mMKM）进行剂量重算。研究发现，为改善大型肿瘤的高LET分布，至少需使HD-CTV中27 cm³（低LET区域）的LET值达到≥33 keV/µm（p<0.05）。因此，我们在治疗计划设计中探索了采用"远端补丁法"的LET优化方案（尚未投入临床使用）。该方法通过创建远端补丁结构，使射束在HD-PTV中心平面外1–2 cm处停止。重新优化计划后，对LEM-I模型下的剂量、mMKM模型下的剂量及LET分布进行重算。结果显示，远端补丁法可提升：（a）HD-CTV的LET中位值（从38±3.4 keV/µm增至47±8.1 keV/µm）；（b）HD-CTV低LET区域的最小LET值（从32±2.3 keV/µm增至36.2±3.6 keV/µm）；（c）肿瘤靶区（GTV）中LET≥50 keV/µm的体积占比（从<10%提升至>50%）；（d）GTV中心区域的高LET组分，且未显著影响剂量分布。然而，远端补丁法对摆位误差和射程不确定性较为敏感，在常规临床应用前需进一步验证其稳健性。

原文链接：

Planning Strategy to Optimize the Dose-Averaged LET Distribution in Large Pelvic Sarcomas/Chordomas Treated with Carbon-Ion Radiotherapy