School of Medical and Health Sciences, Tung Wah College, Hong Kong, China.
Department of Oncology, Kiang Wu Hospital, Macau, China.
Med Dosim. 2022;47(3):288-294. doi: 10.1016/j.meddos.2022.04.005. Epub 2022 May 28.
To evaluate the dosimetric advantages of incorporating the deep inspiration breath hold (DIBH) technique into left breast cancer volumetric modulated arc therapy (VMAT) treatment under Halcyon Linac and to investigate the correlation between mean heart dose (MHD) and distance from the heart to target volumes in left breast cancer VMAT treatment. Fifteen Post-lumpectomy, left-sided breast patients treated between January 2017 and October 2020 were selected. Two plans were generated for each patient using Eclipse treatment planning system (TPS) with the prescription of 50.4 Gy to planning target volume (PTV) breast and 58.8 Gy to PTV boost in 28 fractions. For each patient, DIBH and free breathing (FB) VMAT treatment plans under Halcyon Linac were generated. Dosimetric parameters, monitor unit and beam-on time of both DIBH and FB groups were compared. Three-dimensional distances from heart surface to each target volume were measured on computed tomography images using the TPS contouring tool and their correlation with MHD was evaluated by Pearson's correlation coefficient (r). Comparable target coverage was shown in both groups. Mean dose to heart, left anterior descending artery, and left ventricle in Halcyon-DIBH-VMAT group were significantly reduced by 0.49 Gy, 1.19 Gy, and 0.57 Gy, respectively, compared to Halcyon-FB-VMAT (p < 0.001). A significant lung dose reduction was also achieved in Halcyon-DIBH-VMAT group. There was also a strong negative correlation between MHD and distance from heart surface to PTV boost in both FB and DIBH group (r = -0.741, p < 0.001), but not observed for distance from heart surface to PTV breast. Incorporating DIBH into left breast cancer VMAT treatment under Halcyon Linac demonstrated significant cardiac and lung dose reduction. It was also demonstrated that MHD had a strong negative correlation with distance from heart surface to PTV boost but relatively independent of distance from heart surface to PTV breast. Recognizing the distance from the heart surface to PTV boost as the main factor in affecting MHD could potentially facilitate clinical treatment planning workflow and decision.
评估在 Halcyon 直线加速器下将深吸气屏气（DIBH）技术纳入左侧乳腺癌容积调强弧形治疗（VMAT）中的剂量学优势，并研究左乳腺癌 VMAT 治疗中平均心脏剂量（MHD）与心脏到靶区距离之间的相关性。选择了 2017 年 1 月至 2020 年 10 月期间接受保乳手术后的 15 例左侧乳腺癌患者。使用 Eclipse 治疗计划系统（TPS）为每位患者生成两个计划，处方为 50.4Gy 至计划靶区（PTV）乳房和 58.8Gy 至 PTV 推量 28 分次。为每位患者生成 DIBH 和自由呼吸（FB）Halcyon 直线加速器下的 VMAT 治疗计划。比较了 DIBH 和 FB 两组的剂量学参数、监测单位和射束开启时间。使用 TPS 轮廓工具在 CT 图像上测量心脏表面到每个靶区的三维距离，并通过 Pearson 相关系数（r）评估它们与 MHD 的相关性。两组均显示出可比的靶区覆盖。与 Halcyon-FB-VMAT 相比， Halcyon-DIBH-VMAT 组心脏、左前降支和左心室的平均剂量分别显著降低了 0.49Gy、1.19Gy 和 0.57Gy（p<0.001）。Halcyon-DIBH-VMAT 组还实现了显著的肺剂量降低。在 FB 和 DIBH 组中，MHD 与心脏表面到 PTV 推量的距离之间均存在强烈的负相关（r=−0.741，p<0.001），但在心脏表面到 PTV 乳房的距离上没有观察到这种相关性。在 Halcyon 直线加速器下将 DIBH 纳入左侧乳腺癌 VMAT 治疗中，显示出显著的心脏和肺剂量降低。还表明，MHD 与心脏表面到 PTV 推量的距离之间存在强烈的负相关，但与心脏表面到 PTV 乳房的距离相对独立。将心脏表面到 PTV 推量的距离视为影响 MHD 的主要因素，可能有助于简化临床治疗计划工作流程和决策。
