Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany; Comprehensive Cancer Center Erlangen-EMN (CCC ER-EMN), Erlangen, Bavaria, Germany.
Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany; Comprehensive Cancer Center Erlangen-EMN (CCC ER-EMN), Erlangen, Bavaria, Germany.
Brachytherapy. 2022 Sep-Oct;21(5):635-646. doi: 10.1016/j.brachy.2022.04.007. Epub 2022 May 26.
Seed brachytherapy is a well-established treatment modality for prostate cancer. However, there is still a lack of profound characterizations of seed motions within the prostate. We assessed these dynamics between day 0 and day 30 of brachytherapy.
We considered 45 patients with 2408 implanted seeds, and performed a 1:1 assignment between their positions on post-plan CT (nominal day 30) and intraoperative ultrasound (day 0). Geometric seed arrangement changes were measured for each patient and the entire collective. The impact of seed strand-lengths and implant regions was investigated. Correlations with patient characteristics were evaluated. We determined corresponding dosimetric effects by calculating common dose metrics.
We found a median seed displacement of 4.3 mm [interquartile range: 3.1-6.9 mm], occurring preferentially in superior-inferior direction. Single and double strands moved significantly stronger than strands of higher lengths. Seed dynamics was more pronounced in base (5.6 mm [3.7-10.7 mm]) and apex (6.5 mm [4.1-15.0 mm]) than in the mid-gland (3.8 mm [2.7-5.0 mm]), and less pronounced in peripheral (4.3 mm [3.0-6.7 mm]) than in urethra-near (5.5 mm [3.5-10.7 mm]) regions. Correlations of seed dynamics with prostate volume changes and the number of implanted seeds and needles were found. D (dose that 90% of the prostate receives) varied by a median of 3 Gy [-6 to 15 Gy] between treatment plan and post-plan, but >40 Gy for individual patients.
Reducing seed dynamics is important to ensure a high treatment quality. For this, strands containing ≥3 seeds may be useful, implantations in base-, apex-, and urethra-near zone should be avoided, and the number of needles and seeds may be minimized where possible.
种子近距离放疗是前列腺癌的一种成熟治疗方式。然而，目前对于前列腺内种子的运动仍缺乏深入的研究。本研究评估了近距离放疗第 0 天到第 30 天之间的种子运动情况。
共纳入 45 例患者，共植入 2408 颗种子。我们对这些患者在治疗计划后 CT （名义上的第 30 天）和术中超声（第 0 天）的位置进行 1:1 配对。对每位患者和整个队列的种子位置变化进行了测量。分析了种子链长度和植入区域的影响。评估了与患者特征的相关性。通过计算常见剂量指标，确定了相应的剂量学影响。
我们发现种子的中位数位移为 4.3mm[四分位距：3.1-6.9mm]，主要发生在上下方向。单链和双链种子的移动明显比更长的链强。在底部（5.6mm[3.7-10.7mm]）和顶部（6.5mm[4.1-15.0mm]），种子运动比在中部（3.8mm[2.7-5.0mm]）更为明显，而在周边（4.3mm[3.0-6.7mm]）比在靠近尿道（5.5mm[3.5-10.7mm]）的区域更为不明显。我们发现种子运动与前列腺体积变化以及植入的种子和针的数量存在相关性。与治疗计划相比，D （90%的前列腺接受的剂量）在计划后变化中位数为 3Gy[-6 至 15Gy]，但对于个别患者则超过 40Gy。
减少种子运动对于确保治疗质量非常重要。为此，含有≥3 颗种子的链可能会有所帮助，应避免在底部、顶部和靠近尿道的区域植入，并且应尽可能减少针和种子的数量。
