Portelance Lorraine, Asher David, Llorente Ricardo, Mellon Eric, Wolfson Aaron, Simpson Garrett, Baikovitz Jacqueline, Dogan Nesrin, Padgett Kyle R
Department of Radiation Oncology, University of Miami School of Medicine, Miami, FL, USA.
Department of Radiation Oncology, University of Pittsburgh, Medical Center Altoona, USA.
Phys Med. 2025 Jan;129:104869. doi: 10.1016/j.ejmp.2024.104869. Epub 2024 Dec 12.
Consensus contouring guidelines for intensity-modulated-radiation-therapy (IMRT) of patients with locally advanced cervix cancer (LACC) advise including the whole uterus in the target volume and adding generous planning-target-volumes (PTVs) to account for motion uncertainties of the gross-tumor-volume (GTV). The primary objective of this analysis was to assess the interfractional GTV motions using a magnetic-resonance-image (MRI) guided-Radiation-Therapy (MRgRT) system to investigate the margins required for MRgRT treatments.
125 daily set-up MRIs from five patients with LACC who received MRgRT were analyzed. The GTV, bladder, uterus, and rectum were contoured on all 125 MRIs. Tumor volume changes were calculated in cubic-centimeters (cc). The positional and volume changes of organs-at-risk (OARs) were calculated to assess their effect on GTV interfractional motion, these data were used to calculate adequate PTV margins.
The tumor volume decreased in size during the course of MRgRT for all patients, from 34.0 % to 85.2 %. The interfractional average GTV displacement ranged from 0.46 cm to 0.94 cm. The PTV margins required were: 0.78 cm Left-Right, 1.31 cm Anterior-Posterior and 1.38 cm for the Superior-Inferior directions. The proposed PTV margins, compared to those recommended by consensus guidelines, reduce the PTV by 38 % sparing both the sigmoid and bowel OARs.
By utilizing daily onboard MRI guidance, the GTV becomes readily visualized, allowing for margin reduction and potentially excluding a portion of the uterine fundus from the PTV. The amount of interfractional motion demonstrated in this study is considerable and clinically significant with the goal of decreasing treatment toxicity while maintaining tumor control.
Daily pretreatment magnetic resonance images (MRIs) from patients with locally advanced cervix cancer (LACC) treated with on-board MR-guided radiation therapy (MRgRT) were analyzed to quantify the range of interfractional motion and develop target volume guidelines for adaptive MRgRT. MRI-guidance leads to better tumor visualization in comparison to cone beam computed tomography (CBCT), and online adaptive planning can account for the interfraction motion of the tumor and surrounding tissue. MRI's ability to better visualize the disease and pelvic anatomy along with adaptive on-board MRgRT could allow for a reduction in the required setup margins as well as potentially excluding non-diseased portions of the uterus from the target volumes. These changes will lead to reduced treatment volumes and may lead to decreased treatment toxicities and allow for dose escalation in certain circumstances.
局部晚期宫颈癌（LACC）患者调强放射治疗（IMRT）的共识轮廓指南建议将整个子宫纳入靶区体积，并增加足够的计划靶区体积（PTV）以考虑大体肿瘤体积（GTV）的运动不确定性。本分析的主要目的是使用磁共振成像（MRI）引导放射治疗（MRgRT）系统评估分次间GTV的运动，以研究MRgRT治疗所需的边界。
分析了5例接受MRgRT的LACC患者的125次每日定位MRI。在所有125幅MRI上勾勒出GTV、膀胱、子宫和直肠的轮廓。以立方厘米（cc）计算肿瘤体积变化。计算危及器官（OAR）的位置和体积变化，以评估其对GTV分次间运动的影响，这些数据用于计算合适的PTV边界。
所有患者在MRgRT过程中肿瘤体积均减小，减小幅度为34.0%至85.2%。分次间平均GTV位移范围为0.46 cm至0.94 cm。所需的PTV边界为：左右方向0.78 cm，前后方向1.31 cm，上下方向1.38 cm。与共识指南推荐的边界相比，所建议的PTV边界使PTV减少了38%，从而使乙状结肠和肠等OAR得到了保护。
通过利用每日机载MRI引导，GTV易于可视化，从而可减少边界，并有可能将子宫底部的一部分排除在PTV之外。本研究中显示的分次间运动量相当可观且具有临床意义，其目标是在维持肿瘤控制的同时降低治疗毒性。
分析了接受机载MR引导放射治疗（MRgRT）的局部晚期宫颈癌（LACC）患者的每日治疗前磁共振图像（MRI），以量化分次间运动范围并制定适形MRgRT的靶区体积指南。与锥形束计算机断层扫描（CBCT）相比，MRI引导可使肿瘤可视化更好，并且在线适形计划可考虑肿瘤和周围组织的分次间运动。MRI能够更好地显示疾病和盆腔解剖结构，以及机载适形MRgRT，这可能会减少所需的摆位边界，并有可能将子宫的非病变部分排除在靶区体积之外。这些变化将导致治疗体积减小，并可能降低治疗毒性，并在某些情况下允许增加剂量。
