Chasseray M, Dissaux G, Lucia F, Boussion N, Goasduff G, Pradier O, Bourbonne V, Schick U
Radiation Oncology Department, CHU de Brest, Brest, France.
Radiation Oncology Department, CHU de Brest, Brest, France; LaTIM, INSERM, UMR 1101, CHRU de Brest, Brest, France.
Cancer Radiother. 2020 Apr;24(2):99-105. doi: 10.1016/j.canrad.2019.11.001. Epub 2020 Mar 19.
During radiotherapy (RT) for prostate cancer (PCa), interfraction and intrafraction movements can lead to decreased target dose coverage and unnecessary over-exposure of organs at risk. New image-guided RT techniques accuracy allows planning target volume (PTV) margins reduction. We aim to assess the feasibility of a kilovoltage intrafraction monitoring (KIM) to track the prostate during RT.
Between November 2017 and April 2018, 44 consecutive patients with PCa were included in an intrafraction prostate motion study using the Truebeam Auto Beam Hold® tracking system (Varian Medical Systems, United State) triggered by gold fiducials localization on kilovoltage (kV) imaging. A 5-mm PTV was considered. A significant gating event (SGE) was defined as the occurrence of an automatic beam interruption requiring patient repositioning following the detection of one fiducial outside a 5-mm target area around the marker during more than 45seconds.
Six patients could not benefit from the KIM because of technical issues (loss of one fiducial marker=1, hip prosthesis=4, morbid obesity causing table movements=1). The mean rate of SGE per patient was 14±19%, and the fraction average delivery time was increased by 146±86seconds. For a plan of 39 fractions of 2Gy, the additional radiation dose increased by 0.13±0.09Gy. The mean rates of SGE were 2% and 18% (P=0.002) in patients with planned fraction<90 and>90seconds respectively, showing that duration of the session strongly interfered with prostate intrafraction movements. No other significant clinical and technical parameter was correlated with the occurrence of SGE.
Automated intrafraction kV imaging can effectively perform autobeam holds due to intrafraction movement of the prostate in the large majority of patients. The additional radiation dose and delivery time are acceptable. This technique may be a cost-effective alternative to electromagnetic transponder guidance.
在前列腺癌（PCa）的放射治疗（RT）期间，分次间和分次内的运动可导致靶区剂量覆盖降低以及危及器官不必要的过度照射。新的图像引导放射治疗技术的准确性允许减少计划靶体积（PTV）边界。我们旨在评估千伏分次内监测（KIM）在放疗期间跟踪前列腺的可行性。
在2017年11月至2018年4月期间，连续44例PCa患者被纳入一项分次内前列腺运动研究，该研究使用Truebeam Auto Beam Hold®跟踪系统（美国瓦里安医疗系统公司），通过千伏（kV）成像上的金标记定位触发。考虑设置5毫米的PTV。重大门控事件（SGE）定义为在超过45秒的时间内检测到一个标记物在标记周围5毫米靶区之外时，发生需要患者重新定位的自动束中断。
6例患者由于技术问题（一个标记物丢失=1例，髋关节假体=4例，病态肥胖导致治疗床移动=1例）无法从KIM中获益。每位患者的SGE平均发生率为14±19%，分次平均照射时间增加了146±86秒。对于一个39次、每次2Gy的计划，额外的辐射剂量增加了0.13±0.09Gy。计划分次时间<90秒和>90秒的患者中，SGE的平均发生率分别为2%和18%（P=0.002），表明治疗时间强烈干扰了前列腺的分次内运动。没有其他显著的临床和技术参数与SGE的发生相关。
在大多数患者中，由于前列腺的分次内运动，自动分次内kV成像可以有效地执行自动束保持。额外的辐射剂量和照射时间是可以接受的。该技术可能是电磁应答器引导的一种经济有效的替代方法。
