Lohr Frank, El-Haddad Mostafa, Dobler Barbara, Grau Roland, Wertz Hans-Joerg, Kraus-Tiefenbacher Uta, Steil Volker, Madyan Yasser Abo, Wenz Frederik
Department of Radiation Oncology, Mannheim University Medical Center, University of Heidelberg, Mannheim, Germany.
Int J Radiat Oncol Biol Phys. 2009 May 1;74(1):73-80. doi: 10.1016/j.ijrobp.2008.07.018. Epub 2008 Oct 28.
Three-dimensional (3D) treatment planning has reduced the cardiac dose in postoperative radiotherapy for breast cancer; however, the overall cardiac toxicity is still an issue because of more aggressive adjuvant treatment. Toxicity models have suggested that a reduction of the heart volume treated to high doses might be particularly advantageous. We compared aperture-based multifield intensity-modulated radiotherapy (IMRT) plans to 3D-planned tangent fields using dose-volume histograms, cardiac toxicity risk, and the robustness to positioning errors.
For 14 computed tomography data sets of patients with left-sided breast cancer (unfavorable thoracic geometry), a 3D treatment plan and an IMRT plan were created. The dose-volume histograms were evaluated for the target and risk organs. Excess risk of cardiac mortality was calculated for both approaches using a relative seriality model. Positioning errors were simulated by moving the isocenter.
IMRT reduced the maximal dose to the left ventricle by a mean of 30.9% (49.14 vs. 33.97 Gy). The average heart volume exposed to >30 Gy was reduced from 45 cm(3) to 5.84 cm(3). The mean dose to the left ventricle was reduced by an average of 10.7% (10.86 vs. 9.7 Gy), and the mean heart dose increased by an average of 24% (from 6.85 to 8.52 Gy). The model-based reduction of the probability for excess therapy-associated cardiac death risk was from 6.03% for the 3D plans to 0.25% for the IMRT plans.
Aperture-based IMRT for left-sided breast cancer significantly reduces the maximal dose to the left ventricle, which might translate into reduced cardiac mortality. Biological modeling might aid in deciding to treat with IMRT but has to be validated prospectively.
三维（3D）治疗计划已降低了乳腺癌术后放疗中的心脏剂量；然而，由于辅助治疗更为积极，总体心脏毒性仍是一个问题。毒性模型表明，减少高剂量照射的心脏体积可能特别有益。我们使用剂量体积直方图、心脏毒性风险以及对定位误差的稳健性，将基于孔径的多野调强放疗（IMRT）计划与3D计划的切线野进行了比较。
对于14例左侧乳腺癌患者（胸廓几何形状不佳）的计算机断层扫描数据集，创建了一个3D治疗计划和一个IMRT计划。对靶区和危及器官评估剂量体积直方图。使用相对序列模型计算两种方法的心脏死亡超额风险。通过移动等中心模拟定位误差。
IMRT使左心室的最大剂量平均降低了30.9%（49.14 Gy对33.97 Gy）。暴露于>30 Gy的平均心脏体积从45 cm³降至5.84 cm³。左心室的平均剂量平均降低了10.7%（10.86 Gy对9.7 Gy），平均心脏剂量平均增加了24%（从6.85 Gy增至8.52 Gy）。基于模型的与治疗相关的心脏死亡超额风险概率从3D计划的6.03%降至IMRT计划的0.25%。
基于孔径的IMRT用于左侧乳腺癌可显著降低左心室的最大剂量，这可能转化为心脏死亡率的降低。生物学建模可能有助于决定是否采用IMRT治疗，但必须进行前瞻性验证。
