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Abstract：
BACKGROUND: Limited literature exists on the feasibility and effectiveness of integrating stereotactic ablative radiotherapy (SABR) techniques with hyperfractionated regimens for patients with lung cancer. This study aims to assess whether the SABR technique with hyperfractionation can potentially reduce lung toxicity.
METHODS: We utilized the linear-quadratic model to find the optimal fraction to maximize the tumor biological equivalent dose (BED) to normal-tissue BED ratio. Validation was performed by comparing the SABR plans with 50 Gy/5 fractions and hyperfractionationed plans with 88.8 Gy/74 fractions with the same tumor BED and planning criteria for 10 patients with early-stage lung cancer. Mean lung BED, Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP), critical volume (CV) criteria (volume below BED of 22.92 and 25.65 Gy, and mean BED for lowest 1000 and 1500 cc) and the percentage of the lung receiving 20Gy or more (V20) were compared using the Wilcoxon signed-rank test.
RESULTS: The transition point occurs when the tumor-to-normal tissue ratio (TNR) of the physical dose equals the TNR of α/β in the BED dose-volume histogram of the lung. Compared with the hypofractionated regimen, the hyperfractionated regimen is superior in the dose range above but inferior below the transition point. The hyperfractionated regimen showed a lower mean lung BED (6.40 Gy vs. 7.73 Gy) and NTCP (3.50% vs. 4.21%), with inferior results concerning CV criteria and higher V20 (7.37% vs. 7.03%) in comparison with the hypofractionated regimen (p < 0.01 for all).
CONCLUSIONS: The hyperfractionated regimen has an advantage in the high-dose region of the lung but a disadvantage in the low-dose region. Further research is needed to determine the superiority between hypo- and hyperfractionation.
METHODS: We utilized the linear-quadratic model to find the optimal fraction to maximize the tumor biological equivalent dose (BED) to normal-tissue BED ratio. Validation was performed by comparing the SABR plans with 50 Gy/5 fractions and hyperfractionationed plans with 88.8 Gy/74 fractions with the same tumor BED and planning criteria for 10 patients with early-stage lung cancer. Mean lung BED, Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP), critical volume (CV) criteria (volume below BED of 22.92 and 25.65 Gy, and mean BED for lowest 1000 and 1500 cc) and the percentage of the lung receiving 20Gy or more (V20) were compared using the Wilcoxon signed-rank test.
RESULTS: The transition point occurs when the tumor-to-normal tissue ratio (TNR) of the physical dose equals the TNR of α/β in the BED dose-volume histogram of the lung. Compared with the hypofractionated regimen, the hyperfractionated regimen is superior in the dose range above but inferior below the transition point. The hyperfractionated regimen showed a lower mean lung BED (6.40 Gy vs. 7.73 Gy) and NTCP (3.50% vs. 4.21%), with inferior results concerning CV criteria and higher V20 (7.37% vs. 7.03%) in comparison with the hypofractionated regimen (p < 0.01 for all).
CONCLUSIONS: The hyperfractionated regimen has an advantage in the high-dose region of the lung but a disadvantage in the low-dose region. Further research is needed to determine the superiority between hypo- and hyperfractionation.
摘要：
背景：关于将立体定向消融放疗（SABR）技术与超分割方案整合用于肺癌患者的可行性和有效性的文献有限。本研究旨在评估具有超分割的SABR技术是否可以潜在地降低肺毒性。
方法：我们利用线性二次模型来找到最佳分数，以最大化肿瘤生物等效剂量（BED）与正常组织BED的比率。通过比较具有50Gy/5分数的SABR计划和具有相同肿瘤BED和计划标准的88.8Gy/74分数的超分割计划以及10例早期肺癌患者的计划标准来进行验证。平均肺床,莱曼-库彻-伯曼（LKB）正常组织并发症概率（NTCP），临界体积(CV)标准(体积低于22.92和25.65Gy，使用Wilcoxon符号秩检验比较最低1000和1500cc的平均BED）和接受20Gy或更多（V20）的肺百分比。
结果：当物理剂量的肿瘤与正常组织之比（TNR）等于肺的BED剂量-体积直方图中α/β的TNR时，发生转变点。与低分割方案相比，超分割方案的剂量范围高于过渡点，但低于过渡点。超分割方案显示较低的平均肺BED（6.40Gyvs.7.73Gy）和NTCP（3.50%与4.21%），关于CV标准的结果较差，V20较高(7.37%vs.7.03％）与低分割方案相比（全部p<0.01）。
结论：超分割方案在肺的高剂量区域具有优势，但在低剂量区域具有劣势。需要进一步的研究来确定低分割和高分割之间的优越性。
方法：我们利用线性二次模型来找到最佳分数，以最大化肿瘤生物等效剂量（BED）与正常组织BED的比率。通过比较具有50Gy/5分数的SABR计划和具有相同肿瘤BED和计划标准的88.8Gy/74分数的超分割计划以及10例早期肺癌患者的计划标准来进行验证。平均肺床,莱曼-库彻-伯曼（LKB）正常组织并发症概率（NTCP），临界体积(CV)标准(体积低于22.92和25.65Gy，使用Wilcoxon符号秩检验比较最低1000和1500cc的平均BED）和接受20Gy或更多（V20）的肺百分比。
结果：当物理剂量的肿瘤与正常组织之比（TNR）等于肺的BED剂量-体积直方图中α/β的TNR时，发生转变点。与低分割方案相比，超分割方案的剂量范围高于过渡点，但低于过渡点。超分割方案显示较低的平均肺BED（6.40Gyvs.7.73Gy）和NTCP（3.50%与4.21%），关于CV标准的结果较差，V20较高(7.37%vs.7.03％）与低分割方案相比（全部p<0.01）。
结论：超分割方案在肺的高剂量区域具有优势，但在低剂量区域具有劣势。需要进一步的研究来确定低分割和高分割之间的优越性。
