Institut Curie, Department of Radiation Oncology, Paris, France.
Acta Oncol. 2021 Aug;60(8):1038-1044. doi: 10.1080/0284186X.2021.1907860. Epub 2021 Mar 31.
Proton therapy for breast cancer treatment reduces cardiac radiation exposure. Left-sided breast cancer patients with indication for internal mammary chain (IMC) irradiation are most at risk of radiation-induced cardiotoxicity. This study aims to evaluate in this situation the potential dosimetric benefit of intensity modulated proton therapy (IMPT) over volumetric modulated arc therapy (VMAT) at the cardiac substructure level.
Cardiac substructures were retrospectively delineated according to ESTRO guidelines on the simulation CT scans of fourteen left-sided breast cancer patients having undergone conserving surgery and adjuvant locoregional free-breathing (FB-) or deep inspiration breath-hold (DIBH-) VMAT with internal mammary chain irradiation. IMPT treatment was re-planned on the simulation CT scans. Mean doses to cardiac substructures were retrieved and compared between VMAT treatment plans and IMPT simulation plans. Pearson correlation coefficients were calculated between mean doses delivered to cardiac substructures using these two techniques.
Mean doses to all cardiac substructures were significantly lower with IMPT than with VMAT. Regardless of the irradiation technique, the most exposed cardiac substructure was the mid segment of the left anterior descending coronary artery (LADCA). Pearson correlation coefficients between mean doses to cardiac substructures were usually weak and statistically non-significant for IMPT; mean heart dose (MHD) only correlated with mean doses delivered to the right ventricle, to the mid segment of the right coronary artery (RCA) and, to a lesser extent, to the LADCA.
The dosimetric benefit of IMPT over conformal photon therapy was consistently observed for all cardiac substructures. MHD may not be a reliable dosimetric parameter for precise cardiac exposure evaluation when planning IMPT.
质子治疗乳腺癌可降低心脏的辐射暴露。有内乳链（IMC）照射指征的左侧乳腺癌患者最容易发生放射性心脏毒性。本研究旨在评估在这种情况下，强度调制质子治疗（IMPT）相对于容积调制弧形治疗（VMAT）在心腔亚结构水平上的潜在剂量学优势。
根据 ESTRO 指南，在 14 例接受保乳手术和辅助局部自由呼吸（FB-）或深吸气屏气（DIBH-）VMAT 联合内乳链照射的左侧乳腺癌患者的模拟 CT 扫描上，回顾性地勾画了心脏亚结构。在模拟 CT 扫描上重新规划了 IMPT 治疗计划。比较了 VMAT 治疗计划和 IMPT 模拟计划中心脏亚结构的平均剂量。使用这两种技术，计算了心脏亚结构平均剂量之间的 Pearson 相关系数。
与 VMAT 相比，IMPT 可显著降低所有心脏亚结构的平均剂量。无论照射技术如何，暴露最多的心脏亚结构是左前降支冠状动脉（LADCA）的中段。使用 IMPT 时，心脏亚结构的平均剂量之间的 Pearson 相关系数通常较弱且无统计学意义；仅平均心脏剂量（MHD）与右心室、右冠状动脉（RCA）中段和 LADCA 的平均剂量相关，相关性较弱。
对于所有心脏亚结构，IMPT 相对于常规光子治疗的剂量学优势是一致的。在规划 IMPT 时，MHD 可能不是精确评估心脏暴露的可靠剂量学参数。
