Department of Diagnostic Imaging, The Warren Alpert Medical School, Brown University, Providence, RI, USA.
Molecular Imaging and Therapy Service, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
Cardiovasc Intervent Radiol. 2022 Jul;45(7):958-969. doi: 10.1007/s00270-022-03139-6. Epub 2022 Apr 22.
To determine how particle density affects dose distribution and outcomes after lobar radioembolization.
Matched pairs of patients, treated with glass versus resin microspheres, were selected by propensity score matching (114 patients), in this single-institution retrospective study. For each patient, tumor and liver particle density (particles/cm) and dose (Gy) were determined. Tumor-to-normal ratio was measured on both Tc-MAA SPECT/CT and post-Y bremsstrahlung SPECT/CT. Microdosimetry simulations were used to calculate first percentile dose, which is the dose in the cold spots between microspheres. Local progression-free survival (LPFS) and overall survival were analyzed.
As more particles were delivered, doses on Y SPECT/CT became more uniform throughout the treatment volume: tumor and liver doses became more similar (p = 0.04), and microscopic cold spots between particles disappeared. For hypervascular tumors (tumor-to-normal ratio ≥ 2.6 on MAA scan), delivering fewer particles (< 6000 particles/cm treatment volume) was associated with better LPFS (p = 0.03). For less vascular tumors (tumor-to-normal ratio < 2.6), delivering more particles (≥ 6000 particles/cm) was associated with better LPFS (p = 0.02). In matched pairs of patients, using the optimal particle density resulted in improved overall survival (11.5 vs. 6.8 months, p = 0.047), compared to using suboptimal particle density. Microdosimetry resulted in better predictions of LPFS (p = 0.03), and overall survival (p = 0.02), compared to conventional dosimetry.
The number of particles delivered can be chosen to maximize the tumor dose and minimize the liver dose, based on tumor vascularity. Optimizing the particle density resulted in improved LPFS and overall survival.
确定粒子密度如何影响肺段放射性栓塞后的剂量分布和结果。
通过倾向评分匹配（114 例患者），在这项单中心回顾性研究中选择玻璃微球与树脂微球治疗的配对患者。为每位患者确定肿瘤和肝脏的粒子密度（颗粒/cm）和剂量（Gy）。在 Tc-MAA SPECT/CT 和后-Y 韧致辐射 SPECT/CT 上测量肿瘤与正常组织的比值。使用微剂量模拟计算第一百分位数剂量，即微球之间冷点的剂量。分析局部无进展生存率（LPFS）和总生存率。
随着更多的粒子被输送，Y SPECT/CT 上的剂量在整个治疗体积内变得更加均匀：肿瘤和肝脏的剂量变得更加相似（p=0.04），并且粒子之间的微观冷点消失了。对于富血管肿瘤（MAA 扫描时肿瘤与正常组织的比值≥2.6），输送较少的粒子（<6000 个粒子/cm 治疗体积）与更好的 LPFS 相关（p=0.03）。对于血管较少的肿瘤（肿瘤与正常组织的比值<2.6），输送更多的粒子（≥6000 个粒子/cm）与更好的 LPFS 相关（p=0.02）。在配对患者中，与使用次优粒子密度相比，使用最佳粒子密度可提高总生存率（11.5 个月与 6.8 个月，p=0.047）。微剂量比常规剂量更能预测 LPFS（p=0.03）和总生存率（p=0.02）。
可以根据肿瘤的血管生成情况选择输送的粒子数量，以最大化肿瘤剂量并最小化肝脏剂量。优化粒子密度可提高 LPFS 和总生存率。
