Cuttino Laurie W, Todor Dorin, Pacyna Lynn, Lin Peck-Sun, Arthur Douglas W
Department of Radiation Oncology, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298-0058, USA.
Am J Clin Oncol. 2006 Oct;29(5):474-8. doi: 10.1097/01.coc.0000225409.99284.f2.
This study is an evaluation of the biologic equivalence of the dose prescriptions for brachytherapy and 3-dimensional conformal external beam radiotherapy (3D-CRT) accelerated partial breast irradiation (APBI), using actual patient dose matrix data, and is based on the concept of equivalent uniform biologically effective dose (EUBED). This formalism allows a nonuniform dose distribution to be reduced to an equivalent uniform dose, while also accounting for fraction size.
Five computed tomography scans were selected from a group of patients treated with multicatheter interstitial APBI. Dose matrices for the brachytherapy plans were computed and analyzed with in-house software. For each patient, the EUBED for the brachytherapy dose matrix was generated based on calculations performed at the voxel-level. These EUBED values were then used to calculate the biologically equivalent fraction size for 3D-CRT (eud).
The mean equivalent fraction size (eudmean) and maximum equivalent fraction size (eudmax) were calculated for each patient using 100 different values of the alpha/beta ratio. The eudmean ranged from 3.67 to 3.69 Gy, while the eudmax ranged from 3.79 to 3.82 Gy. For all values of the alpha/beta ratio, the maximum fraction size calculated to deliver a biologically equivalent dose with 3D-CRT was 3.82 Gy, with an equivalent total prescription dose of 38.2 Gy.
Utilizing a wide range of established radiobiological parameters, this study suggests that the maximum fraction size needed to deliver a biologically equivalent dose using 3D-CRT is 3.82 Gy, supporting the continued use of 3.85Gy BID in the current national cooperative trial.
本研究使用实际患者剂量矩阵数据，基于等效均匀生物学有效剂量（EUBED）的概念，对近距离放射治疗和三维适形外照射放疗（3D-CRT）加速部分乳腺照射（APBI）的剂量处方的生物学等效性进行评估。这种形式主义允许将非均匀剂量分布简化为等效均匀剂量，同时也考虑了分次剂量大小。
从一组接受多导管组织间APBI治疗的患者中选择了五次计算机断层扫描。使用内部软件计算并分析近距离放射治疗计划的剂量矩阵。对于每位患者，基于体素水平的计算生成近距离放射治疗剂量矩阵的EUBED。然后使用这些EUBED值来计算3D-CRT的生物学等效分次剂量大小（eud）。
使用100个不同的α/β比值为每位患者计算平均等效分次剂量大小（eudmean）和最大等效分次剂量大小（eudmax）。eudmean范围为3.67至3.69 Gy，而eudmax范围为3.79至3.82 Gy。对于所有α/β比值的值，计算得出的与3D-CRT产生生物学等效剂量的最大分次剂量大小为 3.82 Gy，等效总处方剂量为38.2 Gy
本研究利用广泛的既定放射生物学参数表明，使用3D-CRT产生生物学等效剂量所需的最大分次剂量大小为3.82 Gy，支持在当前国家合作试验中继续使用3.85Gy BID。
