Assessment of delivered dose in prostate cancer patients treated with ultra-hypofractionated radiotherapy on 1.5-Tesla MR-Linac

作者：Linrui Gao, Yuan Tian, Ming-Shuai Wang, Wenlong Xia, Shi-Rui Qin, Yong-Wen Song, Shulian Wang, Yu Tang, Hui Fang, Yuan Tang, Shunan Qi, Ling-Ling Yan, Yue‐Ping Liu, Hao Jing, Bo Chen, Nianzeng Xing, Ye‐Xiong Li, Ningning Lu · 发表于：Frontiers in Oncology · 年份：2023 · DOI：10.3389/fonc.2023.1039901 · 被引用次数：8 · 研究领域：Advanced Radiotherapy Techniques、Prostate Cancer Diagnosis and Treatment、Radiation Therapy and Dosimetry

Objective To quantitatively characterize the dosimetric effects of long on-couch time in prostate cancer patients treated with adaptive ultra-hypofractionated radiotherapy (UHF-RT) on 1.5-Tesla magnetic resonance (MR)-linac. Materials and methods Seventeen patients consecutively treated with UHF-RT on a 1.5-T MR-linac were recruited. A 36.25 Gy dose in five fractions was delivered every other day with a boost of 40 Gy to the whole prostate. We collected data for the following stages: pre-MR, position verification-MR (PV-MR) in the Adapt-To-Shape (ATS) workflow, and 3D-MR during the beam-on phase (Bn-MR) and at the end of RT (post-MR). The target and organ-at-risk contours in the PV-MR, Bn-MR, and post-MR stages were projected from the pre-MR data by deformable image registration and manually adapted by the physician, followed by dose recalculation for the ATS plan. Results Overall, 290 MR scans were collected (85 pre-MR, 85 PV-MR, 49 Bn-MR and 71 post-MR scans). With a median on-couch time of 49 minutes, the mean planning target volume (PTV)-V 95% of all scans was 97.83 ± 0.13%. The corresponding mean clinical target volume (CTV)-V 100% was 99.93 ± 0.30%, 99.32 ± 1.20%, 98.59 ± 1.84%, and 98.69 ± 1.85%. With excellent prostate-V 100% dose coverage, the main reason for lower CTV-V 100% was slight underdosing of seminal vesicles (SVs). The median V 29 Gy change in the rectal wall was -1% (-20%–17%). The V 29 Gy of the rectal wall increased by >15% was observed in one sca...