Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom.
Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom.
Int J Radiat Oncol Biol Phys. 2015 Jul 15;92(4):787-93. doi: 10.1016/j.ijrobp.2015.02.043. Epub 2015 Apr 28.
Focal brachytherapy targeted to an individual lesion(s) within the prostate may reduce side effects experienced with whole-gland brachytherapy. The outcomes of a consensus meeting on focal prostate brachytherapy were used to investigate optimal dosimetry of focal low-dose-rate (LDR) prostate brachytherapy targeted using multiparametric magnetic resonance imaging (mp-MRI) and transperineal template prostate mapping (TPM) biopsy, including the effects of random and systematic seed displacements and interseed attenuation (ISA).
Nine patients were selected according to clinical characteristics and concordance of TPM and mp-MRI. Retrospectively, 3 treatment plans were analyzed for each case: whole-gland (WG), hemi-gland (hemi), and ultra-focal (UF) plans, with 145-Gy prescription dose and identical dose constraints for each plan. Plan robustness to seed displacement and ISA were assessed using Monte Carlo simulations.
WG plans used a mean 28 needles and 81 seeds, hemi plans used 17 needles and 56 seeds, and UF plans used 12 needles and 25 seeds. Mean D90 (minimum dose received by 90% of the target) and V100 (percentage of the target that receives 100% dose) values were 181.3 Gy and 99.8% for the prostate in WG plans, 195.7 Gy and 97.8% for the hemi-prostate in hemi plans, and 218.3 Gy and 99.8% for the focal target in UF plans. Mean urethra D10 was 205.9 Gy, 191.4 Gy, and 92.4 Gy in WG, hemi, and UF plans, respectively. Mean rectum D2 cm(3) was 107.5 Gy, 77.0 Gy, and 42.7 Gy in WG, hemi, and UF plans, respectively. Focal plans were more sensitive to seed displacement errors: random shifts with a standard deviation of 4 mm reduced mean target D90 by 14.0%, 20.5%, and 32.0% for WG, hemi, and UF plans, respectively. ISA has a similar impact on dose-volume histogram parameters for all plan types.
Treatment planning for focal LDR brachytherapy is feasible. Dose constraints are easily met with a notable reduction to organs at risk. Treating smaller targets makes seed positioning more critical.
针对前列腺内单个病变的局灶性近距离放射治疗（Brachytherapy）可能会降低全腺体近距离放射治疗（Brachytherapy）的副作用。使用多参数磁共振成像（mp-MRI）和经会阴模板前列腺图谱（TPM）活检对前列腺局灶性近距离放射治疗共识会议的结果进行了研究，以探讨局灶性低剂量率（LDR）前列腺近距离放射治疗的最佳剂量学，包括随机和系统种子位移以及种子间衰减（ISA）的影响。
根据临床特征和 TPM 与 mp-MRI 的一致性，选择了 9 名患者。回顾性地对每个病例分析了 3 种治疗计划：全腺体（WG）、半腺体（hemi）和超局灶（UF）计划，每个计划的处方剂量为 145Gy，并具有相同的剂量限制。使用蒙特卡罗模拟评估了种子位移和 ISA 对计划的稳健性。
WG 计划使用了平均 28 根针和 81 个种子，hemi 计划使用了 17 根针和 56 个种子，UF 计划使用了 12 根针和 25 个种子。WG 计划中前列腺的平均 D90（目标接受的最小剂量）和 V100（目标接受 100%剂量的百分比）值分别为 181.3Gy 和 99.8%，hemi 计划中半前列腺的分别为 195.7Gy 和 97.8%，UF 计划中局灶靶区的分别为 218.3Gy 和 99.8%。WG、hemi 和 UF 计划中尿道 D10 的平均值分别为 205.9Gy、191.4Gy 和 92.4Gy。WG、hemi 和 UF 计划中直肠 D2cm3 的平均值分别为 107.5Gy、77.0Gy 和 42.7Gy。局灶性计划对种子位移误差更为敏感：标准偏差为 4mm 的随机移位分别减少了 WG、hemi 和 UF 计划中靶区平均 D90 的 14.0%、20.5%和 32.0%。ISA 对所有计划类型的剂量体积直方图参数都有类似的影响。
局灶性 LDR 近距离放射治疗的治疗计划是可行的。通过显著降低危及器官的剂量，很容易满足剂量限制。治疗较小的靶区会使种子定位更加关键。
