COMPATIBILITY OF THE LINEAR-QUADRATIC FORMALISM AND BIOLOGICALLY EFFECTIVE DOSE CONCEPT TO HIGH-DOSE-PER-FRACTION IRRADIATION IN A MURINE TUMOR
COMPATIBILITY OF THE LINEAR-QUADRATIC FORMALISM AND BIOLOGICALLY EFFECTIVE DOSE CONCEPT TO HIGH-DOSE-PER-FRACTION IRRADIATION IN A MURINE TUMOR
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DOI：
10.1016/j.ijrobp.2011.05.034
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发表时间：
2011-12-01
影响因子：
7
通讯作者：
Ogino, Hiroyuki
中科院分区：
文献类型：
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作者：
Otsuka, Shinya;Shibamoto, Yuta;Ogino, Hiroyuki
目的：为了评估线性二次（LQ）模型计算在高剂量范围内的立体定向照射在小鼠肿瘤model.Methods和材料：雌性10周龄Balb/c小鼠轴承1厘米直径的EMT 6肿瘤的后腿中使用。单次剂量10- 2 - 5戈伊与间隔4小时给予2-5次4-13戈伊进行比较。照射后的细胞存活率通过体内体外测定来确定。使用体外EMT 6细胞测定的α/β比值和LQ形式，计算了低分次剂量的等效单次剂量。然后将其与实际测量的低分次剂量的等效单次剂量进行比较。同时比较了这些分次方案，以研究针对实际辐射剂量和生物有效剂量（BED）绘制的剂量-存活曲线的一致性/分歧。根据LQ公式计算的低分次剂量的等效单次剂量在2-或3-分次实验中比实际测量的剂量低21%-31%，在4-或5-分次实验中低27%-42%。分数实验差异均具有显著性。当假设α/β比更高时，差异变得更小。在直接比较的2至5部分的时间表，各自的剂量-反应曲线几乎重叠时，细胞存活率对实际辐射剂量绘制。然而，曲线倾向于向下移动，增加分数的数量时，细胞存活率绘制对BED计算使用α/β比为3.5戈伊在体外EMT 6 cells.Conclusion：转换的hypofractionated辐射剂量到单剂量使用LQ形式主义低估了hypofractionated辐射的体内效应约20%-40%。该差异似乎大于先前体外研究中观察到的差异，并且倾向于随分数增加而增加。BED似乎是一个不可靠的肿瘤反应的措施。(C)2011 Elsevier Inc.
Purpose: To evaluate the compliance of linear-quadratic (LQ) model calculations in the high-dose range as used in stereotactic irradiation in a murine tumor model.Methods and Materials: Female 10-week-old Balb/c mice bearing 1-cm-diameter EMT6 tumors in the hind legs were used. Single doses of 10-25 Gy were compared with 2-5 fractions of 4-13 Gy given at 4-hour intervals. Cell survival after irradiation was determined by an in vivo in vitro assay. Using an alpha/beta ratio determined for in vitro EMT6 cells and the LQ formalism, equivalent single doses for the hypofractionated doses were calculated. They were then compared with actually measured equivalent single doses for the hypofractionated doses. These fractionation schedules were also compared simultaneously to investigate the concordance/divergence of dose-survival curves plotted against actual radiation doses and biologically effective doses (BED).Results: Equivalent single doses for hypofractionated doses calculated from LQ formalism were lower than actually measured doses by 21%-31% in the 2- or 3-fraction experiments and by 27%-42% in the 4- or 5-fraction experiments. The differences were all significant. When a higher alpha/beta ratio was assumed, the discrepancy became smaller. In direct comparison of the 2- to 5-fraction schedules, respective dose-response curves almost overlapped when cell survival was plotted against actual radiation doses. However, the curves tended to shift downward by increasing the fraction number when cell survival was plotted against BED calculated using an alpha/beta ratio of 3.5 Gy for in vitro EMT6 cells.Conclusion: Conversion of hypofractionated radiation doses to single doses using the LQ formalism underestimated the in vivo effect of hypofractionated radiation by approximately 20%-40%. The discrepancy appeared to be larger than that seen in the previous in vitro study and tended to increase with the fraction number. BED appeared to be an unreliable measure of tumor response. (C) 2011 Elsevier Inc.