Department of Radiation Oncology, institut Curie, 26, rue d'Ulm, 75005 Paris, France.
Department of Radiation Oncology, institut Curie, 26, rue d'Ulm, 75005 Paris, France.
Cancer Radiother. 2021 Feb;25(1):13-20. doi: 10.1016/j.canrad.2020.05.016. Epub 2020 Dec 4.
Rotational intensity-modulated radiation therapy currently has a growing role in breast cancer radiation therapy, since this radiation technique reduces cardiac radiation exposure while homogeneously covering target volumes. This study aims to evaluate radiation exposure of cardiac substructures across a broad spectrum of breast cancer cases differing by cancer laterality, fractionation regimen and addition of deep-inspiration breath hold.
Cardiac substructures were delineated following guidelines endorsed by the European Society for Radiotherapy and Oncology (ESTRO) for forty-four breast cancer patients having undergone conserving surgery and adjuvant rotational intensity-modulated radiation therapy. Target volumes consisted of the whole breast with a boost, axillary and internal mammary nodes. Patients were treated using free-breathing technique for left-sided or right-sided, normofractionated or hypofractionated helical tomotherapy or volumetric modulated arc therapy, or using deep-inspiration breath hold for left-sided normofractionated volumetric modulated arc therapy. Mean and maximum doses to cardiac substructures were retrieved. Correlations were performed between mean- and maximum radiation doses to cardiac substructures.
Left-sided and right-sided irradiations were associated with different cardiac substructure exposure patterns despite comparable mean heart dose: 7.21Gy for left-sided normofractionated regimen, 6.28Gy for right-sided normofractionated regimen. Deep-inspiration breath hold reduced mean doses to almost all cardiac substructures for left-sided irradiation, but did not decrease maximum doses to coronary arteries. Correlations between mean- and maximum doses to cardiac substructures were usually moderate, but stronger for right-sided irradiation.
Despite comparable mean heart dose, cardiac substructure radiation exposure patterns with rotational intensity-modulated radiation therapy strongly depend on the breast side, which could trigger clinically different long-term cardiotoxicity events. Deep-inspiration breath hold improves cardiac substructure dosimetry. Mean- and maximum heart dose could probably not be used as surrogate markers for precise cardiac substructure evaluation. In a near future, clinical practice and cardiotoxicity studies could possibly gain by considering cardiac substructure in a more systematic manner, possibly relying on cardiac autosegmentation algorithms.
旋转调强放疗（rotational intensity-modulated radiation therapy，RIMRT）在乳腺癌放疗中应用日益广泛，因为这种放疗技术可以降低心脏的辐射暴露，同时均匀覆盖靶区。本研究旨在评估广泛乳腺癌病例中，心脏亚结构的辐射暴露情况，这些病例在乳腺癌侧、分割方案和深吸气屏气的应用上存在差异。
为了评估 44 例接受保乳手术和辅助调强放疗的乳腺癌患者的心脏亚结构，我们遵循了欧洲放射肿瘤学会（European Society for Radiotherapy and Oncology，ESTRO）的指南进行了心脏亚结构的勾画。靶区包括全乳、腋窝和内乳淋巴结。患者接受左侧或右侧、常规分割或适形调强放疗（helical tomotherapy）或容积调强弧形治疗（volumetric modulated arc therapy，VMAT）的自由呼吸技术治疗，或接受左侧常规分割 VMAT 的深吸气屏气技术治疗。我们检索了心脏亚结构的平均剂量和最大剂量。我们对心脏亚结构的平均剂量和最大剂量之间进行了相关性分析。
尽管心脏平均剂量相似（左侧常规分割 7.21Gy，右侧常规分割 6.28Gy），但左侧和右侧照射与不同的心脏亚结构暴露模式相关。深吸气屏气降低了左侧照射时几乎所有心脏亚结构的平均剂量，但对冠状动脉的最大剂量没有降低。心脏亚结构的平均剂量和最大剂量之间的相关性通常是中度的，但右侧照射时更强。
尽管心脏平均剂量相似，但旋转调强放疗的心脏亚结构辐射暴露模式强烈依赖于乳房侧，这可能引发临床上不同的长期心脏毒性事件。深吸气屏气可改善心脏亚结构的剂量学。心脏平均剂量和最大剂量可能不能作为精确的心脏亚结构评估的替代标志物。在不久的将来，临床实践和心脏毒性研究可能会受益于更系统地考虑心脏亚结构，可能依赖于心脏自动分割算法。
