Background: Radiotherapy for thymoma is delivered post-operatively in selected cases. Given the particular location of the thymic bed and the excellent prognosis, late cardiac toxicities may be an issue. The purpose of this retrospective dosimetric study is to investigate whether intensity-modulated proton beam therapy (IMPT) compared to photon therapy could better spare cardiac substructures, given prespecified dose constraints. Methods: We retrospectively selected patients treated with adjuvant radiotherapy for thymoma in our institution. We manually contoured fourteen cardiac substructures (CSs), with the supervision of a team of cardioradiologists. The photon-based plans were re-optimized in adherence to the volumetric modulated arc therapy (VMAT) technique with specific dose constraints for the new contoured structures. The proton-based plans were optimized in adherence to intensity-modulated proton therapy (IMPT) using the beam spot scanning technique. Results: Twenty-nine patients treated with adjuvant radiotherapy with a prescribed dose of 50 Gy in 25 daily fractions for radically resected thymoma were selected. IMPT demonstrated better sparing of most cardiac substructures in terms of Dmax, Dmeanand V5Gy. Finally, IMPT plans more easily achieved the proposed dose constraints. Conclusions: Cardiac substructures can be successfully spared with IMPT. Clinical studies are needed to establish a relationship between dose parameters and the development of cardiac events.
背景：胸腺瘤放疗通常在特定病例术后进行。考虑到胸腺床的特殊解剖位置及患者良好的预后，远期心脏毒性可能成为潜在问题。本回顾性剂量学研究旨在探讨，在预设剂量限制条件下，与光子放疗相比，调强质子束治疗（IMPT）是否能更好地保护心脏亚结构。 方法：我们回顾性选取在本机构接受辅助放疗的胸腺瘤患者。在心脏放射学专家团队的指导下，我们手动勾画了十四个心脏亚结构。基于光子治疗的计划按照容积旋转调强放疗（VMAT）技术重新优化，并对新勾画结构设定了特定剂量限制。质子治疗计划则采用点扫描技术，按照调强质子治疗（IMPT）标准进行优化。 结果：共纳入29例接受根治性切除术后辅助放疗的胸腺瘤患者，处方剂量为50 Gy/25次。在Dmax、Dmean和V5Gy等剂量参数方面，IMPT对大多数心脏亚结构显示出更好的保护效果。最终，IMPT计划更易达到预设的剂量限制标准。 结论：IMPT能有效保护心脏亚结构。未来需要通过临床研究建立剂量参数与心脏事件发生之间的关联性。
肿瘤(癌症)患者之家