Proton therapy presents a promising modality for treating left-sided breast cancer due to its unique dose distribution. Helium ions provide increased conformality thanks to a reduced lateral scattering. Consequently, the potential clinical benefit of both techniques was explored. An explorative treatment planning study involving ten patients, previously treated with VMAT (Volumetric Modulated Arc Therapy) for 50 Gy in 25 fractions for locally advanced, node-positive breast cancer, was carried out using proton pencil beam therapy with a fixed relative biological effectiveness (RBE) of 1.1 and helium therapy with a variable RBE described by the mMKM (modified microdosimetric kinetic model). Results indicated that target coverage was improved with particle therapy for both the clinical target volume and especially the internal mammary lymph nodes compared to VMAT. Median dose value analysis revealed that proton and helium plans provided lower dose on the left anterior descending artery (LAD), heart, lungs and right breast than VMAT. Notably, helium therapy exhibited improved ipsilateral lung sparing over protons. Employing NTCP models as available in the literature, helium therapy showed a lower probability of grade ≤ 2 radiation pneumonitis (22% for photons, 5% for protons and 2% for helium ions), while both proton and helium ions reduce the probability of major coronary events with respect to VMAT.
质子治疗因其独特的剂量分布特性，为左侧乳腺癌治疗提供了一种前景广阔的治疗方式。氦离子束凭借其更低的侧向散射效应，能够实现更高的剂量适形度。本研究旨在探索这两种技术的潜在临床优势。我们开展了一项探索性治疗计划研究，纳入了十例既往接受容积旋转调强放疗（VMAT）的局部晚期淋巴结阳性乳腺癌患者（处方剂量为50 Gy/25次）。研究采用固定相对生物效能（RBE=1.1）的质子笔形束治疗，以及基于改良微剂量学动力学模型（mMKM）计算可变RBE的氦离子治疗进行计划设计。结果显示，与VMAT相比，粒子治疗在临床靶区（特别是内乳淋巴结）的靶区覆盖度方面表现更优。中位剂量分析表明，质子与氦离子计划对左前降支动脉、心脏、双肺及右侧乳腺的照射剂量均低于VMAT。值得注意的是，氦离子治疗在保护同侧肺组织方面优于质子治疗。通过应用文献中现有的正常组织并发症概率模型分析，氦离子治疗发生≤2级放射性肺炎的概率更低（光子治疗为22%，质子治疗为5%，氦离子治疗为2%），同时质子与氦离子治疗均能降低主要冠状动脉事件的发生概率，效果优于VMAT。
Exploring Helium Ions’ Potential for Post-Mastectomy Left-Sided Breast Cancer Radiotherapy
肿瘤(癌症)患者之家