Polders Daniel L, Steggerda Marcel, van Herk Marcel, Nichol Kiri, Witteveen Thelma, Moonen Luc, Nijkamp Jasper, van der Heide Uulke A
Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital , Amsterdam , The Netherlands.
Acta Oncol. 2015 Jun;54(6):839-46. doi: 10.3109/0284186X.2014.995312. Epub 2015 Jan 16.
The efficacy of focal continuous low dose-rate brachytherapy (CLDR-BT) for prostate cancer requires that appropriate margins are applied to ensure robust target coverage. In this study we propose a method to establish such margins by emulating a focal treatment in patients treated with CLDR-BT to the entire gland.
In 15 patients with localized prostate cancer, prostate volumes and dominant intra-prostatic lesions were delineated on pre-treatment magnetic resonance imaging (MRI). Delineations and MRI were registered to trans-rectal ultrasound images in the operating theater. The patients received CLDR-BT treatment to the total prostate volume. The implantation consisted of two parts: an experimental focal plan covering the dominant intra-prostatic lesion (F-GTV), followed by a plan containing additional seeds to achieve entire prostate coverage. Isodose surfaces were reconstructed using follow-up computed tomography (CT). The focal dose was emulated by reconstructing seeds from the focal plan only. The distance to agreement between planned and delivered isodose surfaces and F-GTV coverage was determined to calculate the margin required for robust treatment.
If patients had been treated only focally, the target volume would have been reduced from an average of 40.9 cm3 for the entire prostate to 5.8 cm3 for the focal plan. The D90 for the F-GTV in the focal plan was 195±60 Gy, the V100 was 94% [range 71-100%]. The maximum distance (cd95) between the planned and delivered isodose contours was 0.48 cm.
This study provides an estimate of 0.5 cm for the margin required for robust coverage of a focal target volume prior to actually implementing a focal treatment protocol.
聚焦连续低剂量率近距离放射治疗（CLDR-BT）对前列腺癌的疗效要求应用适当的边界以确保对靶区的可靠覆盖。在本研究中，我们提出一种方法，通过模拟对整个腺体进行CLDR-BT治疗的患者的聚焦治疗来确定此类边界。
在15例局限性前列腺癌患者中，在治疗前的磁共振成像（MRI）上勾勒出前列腺体积和前列腺内主要病变。在手术室中，将勾勒结果和MRI与经直肠超声图像进行配准。患者接受了对整个前列腺体积的CLDR-BT治疗。植入分为两部分：一个实验性聚焦计划，覆盖前列腺内主要病变（F-GTV），随后是一个包含额外籽源以实现整个前列腺覆盖的计划。使用随访计算机断层扫描（CT）重建等剂量面。仅从聚焦计划中重建籽源来模拟聚焦剂量。确定计划等剂量面与实际 delivered等剂量面之间的一致性距离以及F-GTV覆盖情况，以计算可靠治疗所需的边界。
如果仅对患者进行聚焦治疗，靶体积将从整个前列腺的平均40.9 cm³减少到聚焦计划的5.8 cm³。聚焦计划中F-GTV的D90为195±60 Gy，V100为94%[范围71 - 100%]。计划等剂量轮廓与实际 delivered等剂量轮廓之间的最大距离（cd95）为0.48 cm。
本研究在实际实施聚焦治疗方案之前，对聚焦靶体积可靠覆盖所需的边界估计为0.5 cm。
