Cooper Benjamin T, Li Xiaochun, Shin Samuel M, Modrek Aram S, Hsu Howard C, DeWyngaert J K, Jozsef Gabor, Lymberis Stella C, Goldberg Judith D, Formenti Silvia C
Department of Radiation Oncology, New York University School of Medicine and Langone Medical Center, New York, New York.
Division of Biostatistics and Department of Population Health, New York University School of Medicine, New York, New York.
Adv Radiat Oncol. 2016 Aug 9;1(4):373-381. doi: 10.1016/j.adro.2016.08.001. eCollection 2016 Oct-Dec.
Maximum dose to the left anterior descending artery (LADmax) is an important physical constraint to reduce the risk of cardiovascular toxicity. We generated a simple algorithm to guide the positioning of the tangent fields to reliably maintain LADmax <10 Gy.
Dosimetric plans from 146 consecutive women treated prone to the left breast enrolled in prospective protocols of accelerated whole breast radiation therapy, with a concomitant daily boost to the tumor bed (40.5 Gy/15 fraction to the whole breast and 48 Gy to the tumor bed), provided the training set for algorithm development. Scatter plots and correlation coefficients were used to describe the bivariate relationships between LADmax and several parameters: distance from the tumor cavity to the tangent field edge, cavity size, breast separation, field size, and distance from the tangent field. A logistic sigmoid curve was used to model the relationship of LADmax and the distance from the tangent field. Furthermore, we tested this prediction model on a validation data set of 53 consecutive similar patients.
A lack of linear relationships between LADmax and distance from cavity to LAD (-0.47), cavity size (-0.18), breast separation (-0.02), or field size (-0.28) was observed. In contrast, distance from the tangent field was highly negatively correlated to LADmax (-0.84) and was used in the models to predict LADmax. From a logistic sigmoid model we selected a cut-point of 2.46 mm (95% confidence interval, 2.19-2.74 mm) greater than which LADmax is <10 Gy (95% confidence interval, 9.30-10.72 Gy) and LADmean is <3.3 Gy.
Placing the edge of the tangents at least 2.5 mm from the closest point of the contoured LAD is likely to assure LADmax is <10 Gy and LADmean is <3.3 Gy in patients treated with prone accelerated breast radiation therapy.
左前降支动脉的最大剂量（LADmax）是降低心血管毒性风险的一个重要物理限制因素。我们生成了一种简单算法，以指导切线野的定位，从而可靠地将LADmax维持在<10 Gy。
146例连续接受左侧乳腺俯卧位治疗的女性患者的剂量计划构成了算法开发的训练集，这些患者参加了加速全乳放疗的前瞻性方案，同时每日对瘤床进行加量照射（全乳40.5 Gy/15次分割，瘤床48 Gy）。散点图和相关系数用于描述LADmax与几个参数之间的双变量关系：从肿瘤腔到切线野边缘的距离、腔大小、乳腺间距、野大小以及到切线野的距离。采用逻辑S形曲线对LADmax与到切线野的距离之间的关系进行建模。此外，我们在53例连续的类似患者的验证数据集上测试了该预测模型。
观察到LADmax与从腔到左前降支的距离（-0.47）、腔大小（-0.18）、乳腺间距（-0.02）或野大小（-0.28）之间缺乏线性关系。相比之下，到切线野的距离与LADmax高度负相关（-0.84），并在模型中用于预测LADmax。从逻辑S形模型中，我们选择了2.46 mm的切点（95%置信区间，2.19 - 2.74 mm），大于该切点时，LADmax <10 Gy（95%置信区间，9.30 - 10.72 Gy）且LADmean <3.3 Gy。
在接受俯卧位加速乳腺放疗的患者中，将切线野边缘置于距勾画的左前降支最接近点至少2.5 mm处，可能确保LADmax <10 Gy且LADmean <3.3 Gy。
