Aparicio Daniel Zucca, Requejo Ovidio Hernando, de Julián Miguel Ángel de la Casa, Rodríguez Carmen Rubio, Letón Pedro Fernández
Servicio de Radiofísica y Protección Radiológica, Hospital Universitario HM Sanchinarro, Oña, 10, 28050 Madrid, Spain.
Servicio de Oncología Radioterápica, Hospital Universitario HM Sanchinarro, Oña, 10, 28050 Madrid, Spain.
Rep Pract Oncol Radiother. 2019 Mar-Apr;24(2):142-150. doi: 10.1016/j.rpor.2019.01.001. Epub 2019 Jan 22.
To evaluate dose differences in lung metastases treated with stereotactic body radiotherapy (SBRT), and the correlation with local control, regarding the dose algorithm, target volume and tissue density.
Several studies showed excellent local control rates in SBRT for lung metastases, with different fractionation schemes depending on the tumour location or size. These results depend on the dose distributions received by the lesions in terms of the tissue heterogeneity corrections performed by the dose algorithms.
Forty-seven lung metastases treated with SBRT, using intrafraction control and respiratory gating with internal fiducial markers as surrogates (, ), were calculated using Pencil Beam (PB) and Monte Carlo (MC) (, ).Dose differences between both algorithms were obtained for the dose received by 99% ( ) and 50% ( ) of the planning treatment volume (PTV). The biologically effective dose delivered to 99% (BED) and 50% (BED) of the PTV were estimated from the MC results. Local control was evaluated after 24 months of median follow-up (range: 3-52 months).
The greatest variations (40.0% in Δ and 38.4% in Δ ) were found for the lower volume and density cases. The BED and BED were strongly correlated with observed local control rates: 100% and 61.5% for BED > 85 Gy and <85 Gy ( < 0.0001), respectively, and 100% and 58.3% for BED > 100 Gy and <100 Gy ( < 0.0001), respectively.
Lung metastases treated with SBRT, with delivered BED > 85 Gy and BED > 100 Gy, present better local control rates than those treated with lower BED values ( = 0.001).
评估立体定向体部放疗（SBRT）治疗肺转移瘤时的剂量差异，以及剂量算法、靶区体积和组织密度与局部控制之间的相关性。
多项研究表明，SBRT治疗肺转移瘤的局部控制率极佳，根据肿瘤位置或大小采用不同的分割方案。这些结果取决于剂量算法对组织异质性校正后病变所接受的剂量分布。
对47例接受SBRT治疗的肺转移瘤进行研究，采用分次内控制和呼吸门控，以内部基准标记物作为替代物（，），使用铅笔束（PB）和蒙特卡罗（MC）（，）进行计算。获得两种算法在计划治疗体积（PTV）的99%（）和50%（）所接受剂量之间的剂量差异。根据MC结果估算PTV的99%（BED）和50%（BED）所给予的生物等效剂量。在中位随访24个月（范围：3 - 52个月）后评估局部控制情况。
在体积较小和密度较低的病例中发现最大差异（Δ中为40.0%，Δ中为38.4%）。BED和BED与观察到的局部控制率密切相关：BED > 85 Gy时局部控制率为100%，BED < 85 Gy时为61.5%（< 0.0001）；BED > 100 Gy时局部控制率为100%，BED < 100 Gy时为58.3%（< 0.0001）。
接受SBRT治疗且BED > 85 Gy和BED > 100 Gy的肺转移瘤，其局部控制率优于BED值较低的情况（ = 0.001）。
