Department of Radiation Oncology, Jeju National University Hospital, Jeju National University College of Medicine, Jeju, Republic of Korea.
Medical Course, Jeju National University College of Medicine, Jeju, Republic of Korea.
In Vivo. 2024 Mar-Apr;38(2):849-854. doi: 10.21873/invivo.13510.
BACKGROUND/AIM: This study aimed to analyze the dosimetric effects of jaw tracking during Volumetric Modulated Arc Therapy (VMAT) planning for facial non-melanoma skin cancer (NMSC).
This study included 50 patients with facial NMSC who underwent VMAT planning with or without jaw tracking. The target volume (TV) included the primary skin lesion with a 1-cm margin around the surface and a depth of 4 mm. A total of 55 Gy in 20 fractions was prescribed, and the plans were considered acceptable if the TV was covered by 95-105% of the isodose curve. A dosimetric comparison was performed for the volumes of the low-dose regions, which were defined as <50% of the prescription dose (V10-50%). Target coverage was evaluated using the homogeneity index (HI) and conformity index (CI).
The patients' mean TV was 5.137 cc (range=1.03-15.89 cc). Jaw tracking resulted in mean volume reduction rates of 3.9%, 6.6% 10.6% and 13.8% for V40%, V30%, V20%, and V10%, respectively (all p<0.001). The volume change in V50% between the two groups was 2.7% (p=0.006). No significant differences were observed in HI (p=0.449) or CI (p=0.127).
The application of jaw tracking during VMAT for facial NMSC is associated with a significant reduction in the volume of low dose delivered in the radiation field (V10-50%), while maintaining target coverage. Future analyses should assess whether this volume difference affects treatment-related cosmetic outcomes.
背景/目的：本研究旨在分析面部非黑色素瘤皮肤癌（NMSC）容积调强弧形治疗（VMAT）计划中使用下颌跟踪的剂量学影响。
本研究纳入了 50 例面部 NMSC 患者，他们接受了有或没有下颌跟踪的 VMAT 计划。靶区（TV）包括原发性皮肤病变，周围表面有 1cm 边界，深度为 4mm。总剂量为 55Gy，分为 20 个分次，当 TV 被 95-105%的等剂量曲线覆盖时，认为计划是可接受的。对低剂量区域的体积进行了剂量比较，低剂量区域定义为<50%的处方剂量（V10-50%）。使用均匀性指数（HI）和适形性指数（CI）评估靶区覆盖情况。
患者的 TV 平均为 5.137cc（范围为 1.03-15.89cc）。下颌跟踪导致 V40%、V30%、V20%和 V10%的平均体积减少率分别为 3.9%、6.6%、10.6%和 13.8%（均 p<0.001）。两组之间 V50%的体积变化为 2.7%（p=0.006）。HI（p=0.449）或 CI（p=0.127）无显著差异。
在面部 NMSC 的 VMAT 中应用下颌跟踪与辐射野中低剂量（V10-50%）的体积显著减少相关，同时保持靶区覆盖。未来的分析应评估这种体积差异是否会影响与治疗相关的美容结果。
