Ding Shouliang, Piao Zun, Chen Meining, Li Fanghua, Li Yongbao, Liu Biaoshui, Liu Hongdong, Huang Xiaoyan, Li Junyun
State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou 510060, PR China.
United Laboratory of Frontier Radiotherapy Technology of Sun Yat-sen University & Chinese Academy of Sciences Ion Medical Technology Co., Ltd, Guangzhou 510060, PR China.
Clin Transl Radiat Oncol. 2024 Oct 29;50:100881. doi: 10.1016/j.ctro.2024.100881. eCollection 2025 Jan.
The aim of this study was to evaluate the inter- and intrafractional organs motions and dosimetric advantages of MRI guided online adaptive radiotherapy for cervical cancer.
A total of 150 fractions treated on the 1.5 T Unity MR-Linac were included in this study. Each fraction, pre-treatment, position validation and post-treatment MRI scans were obtained. Structures including CTV, rectum and bladder were delineated by the same radiation oncologists on each MRI. The inter- and intrafractional changes of contours were assessed by Hausdorff distance (HD), dice similarity coefficient (DSC), relative volume difference (ΔV) and the relative positions of the geometric center. The non-ART plans and online adaptive plans were obtained by recalculating or re-optimizing from reference plans on daily MRI, respectively. CTV coverage and OARs constraints were evaluated between ART and non-ART plans.
For each fraction, the interfractional changes of HD, ΔV and DSC for CTV, bladder and rectum were significant. Our study also examined the relationship of bladder and rectum filling on CTV position. For 150 non-ART plans, CTV coverage constraints (D ≥ 45 Gy) were not met by 45 %, while 15 % were not covered by more than 5 % of the prescribed dose. Compared to the non-ART plans, the ART plans had higher CTV coverage and lower dose to the bladder and rectum (P < 0.05). During the treatment, the intrafractional changes of bladder, rectum and CTV may affect actual dose delivery. And we observed an intrafractional time trend in the motion of the CTV. There were 15 % fractions failing the CTV coverage constraints in post-MRI due to intrafractional motion. The adaptive plans optimized with 3 mm margin could cover CTV of post-MRI in 98 % fractions.
Considerable inter- and intrafractional CTV and OARs changes were observed in cervical cancer patients treated on MR-Linac. MRI guided online ART has significant dosimetric advantages in cervical cancer and is an ideal approach for achieving individualized and precise radiotherapy.
本研究旨在评估MRI引导的宫颈癌在线自适应放疗中分次间和分次内器官运动情况及剂量学优势。
本研究纳入了在1.5T Unity MR直线加速器上治疗的150个分次。每次分次均获取治疗前、位置验证和治疗后MRI扫描图像。相同的放射肿瘤学家在每次MRI图像上勾画出包括临床靶区（CTV）、直肠和膀胱在内的结构。通过豪斯多夫距离（HD）、骰子相似系数（DSC）、相对体积差异（ΔV）以及几何中心的相对位置来评估轮廓的分次间和分次内变化。非自适应放疗计划和在线自适应计划分别通过在每日MRI图像上从参考计划重新计算或重新优化得到。在自适应放疗计划和非自适应放疗计划之间评估CTV覆盖情况和危及器官（OARs）的剂量限制。
对于每个分次，CTV、膀胱和直肠的HD、ΔV和DSC在分次间的变化均具有显著性。我们的研究还探讨了膀胱和直肠充盈对CTV位置的影响。对于150个非自适应放疗计划，45%未满足CTV覆盖剂量限制（D≥45 Gy），而15%未被超过处方剂量的5%覆盖。与非自适应放疗计划相比，自适应放疗计划具有更高的CTV覆盖率，且膀胱和直肠所受剂量更低（P<0.05）。在治疗过程中，膀胱、直肠和CTV的分次内变化可能会影响实际剂量传递。并且我们观察到CTV运动存在分次内时间趋势。由于分次内运动，有15%的分次在MRI后未满足CTV覆盖剂量限制。采用3mm边界优化的自适应计划能够在98%的分次中覆盖MRI后的CTV。
在MR直线加速器上治疗的宫颈癌患者中观察到了显著的分次间和分次内CTV及OARs变化。MRI引导的在线自适应放疗在宫颈癌中具有显著的剂量学优势，是实现个体化精确放疗的理想方法。
