Department of Radiation Oncology, RWTH Aachen University, Pauwelsstraße 30, 52072, Aachen, Germany.
Strahlenther Onkol. 2019 May;195(5):383-392. doi: 10.1007/s00066-018-1381-4. Epub 2018 Oct 17.
To assess the reproducibility of the dose-volume distribution of the initial simulation CT, generated using volumetric modulated arc therapy (VMAT) planning, during the radiotherapy of the prostatic bed based on weekly cone beam CTs (CBCT).
Twenty-three patients, after radical prostatectomy were treated with adjuvant or salvage radiotherapy between July and December 2016 and considered for this evaluation. Weekly CBCT scans (n = 138) were imported into the treatment planning system, and the clinical tumor volume (CTV), the rectum and the bladder were contoured. The initially calculated dose distribution and the dose-volume histograms generated from weekly CBCTs were compared. The prostatic fossa dose coverage was assessed by the proportion of the CTV fully encompassed by the 95% and 98% isodose lines. Rectal and bladder volumes receiving 50, 60 and 65 Gy during the treatment were compared to the initial plan, with statistical significance determined using the one-sample t‑test.
Marked variations in the total organ volume of the rectum and the bladder were observed. The correlation between rectum volume and V was not significant (p = 0.487), while the bladder volume and V demonstrated a significant correlation. There was no correlation between urinary bladder volume and CTV. The change in rectal volume correlated significantly with CTV. The dose coverage (D and D) to the prostatic bed could be achieved for all patients due to the ventral shift in the volume differences of the rectum.
Weekly CBCTs can be considered as adequate verification tools to assess the interfractional variability of the CTV and organs at risk. The proven volume changes in the urinary bladder and the rectum do not compromise the final delivered dose in the CTV.
评估容积调强弧形治疗（VMAT）计划初始模拟 CT 剂量-体积分布在前列腺床放射治疗中的可重复性，该治疗基于每周锥形束 CT（CBCT）。
2016 年 7 月至 12 月，23 例接受根治性前列腺切除术的患者接受辅助或挽救性放疗，并考虑进行此项评估。每周的 CBCT 扫描（n=138）被导入治疗计划系统，并对临床肿瘤体积（CTV）、直肠和膀胱进行勾画。比较最初计算的剂量分布和每周 CBCT 生成的剂量-体积直方图。通过 CTV 完全被 95%和 98%等剂量线覆盖的比例来评估前列腺窝的剂量覆盖。比较直肠和膀胱在治疗过程中分别接受 50、60 和 65Gy 的体积与初始计划，使用单样本 t 检验确定统计学意义。
观察到直肠和膀胱的总器官体积有明显变化。直肠体积与 V 之间的相关性不显著（p=0.487），而膀胱体积与 V 之间存在显著相关性。膀胱体积与 CTV 之间无相关性。直肠体积的变化与 CTV 显著相关。由于直肠体积差异的腹侧移位，所有患者的前列腺床剂量覆盖（D 和 D）均可实现。
每周的 CBCT 可被视为评估 CTV 和危及器官的分次间变异性的充分验证工具。膀胱和直肠的体积变化已被证明不会影响 CTV 的最终剂量。
