Palmqvist Tomas, Dybdahl Wanderås Anne, Langeland Marthinsen Anne Beate, Sundset Marit, Langdal Ingrid, Danielsen Signe, Toma-Dasu Iuliana
Department of Medical Physics, Karolinska University Hospital , Stockholm , Sweden.
Acta Oncol. 2014 Aug;53(8):1012-8. doi: 10.3109/0284186X.2014.928829. Epub 2014 Jun 30.
To compare five inverse treatment planning methods with the conventional manually optimized planning approach for brachytherapy of cervical cancer with respect to dosimetric parameters.
Eighteen cervical cancer patients treated with magnetic resonance imaging (MRI)-guided high dose rate (HDR) brachytherapy were included in this study. Six plans were created for each of the 4 HDR brachytherapy fractions for each patient: 1 manually optimized and 5 inversely planned. Three of these were based on inverse planning simulated annealing (IPSA) with and without extra constraints on maximum doses of the target volume, and different constraints on doses to the organs at risk (OARs). In addition there were two plans based on dose to target surface points. The resulting dose-volume histograms were analyzed and compared from the dosimetric point of view by quantifying specific dosimetric parameters, such as clinical target volume (CTV) D₉₀, CTV D₁₀₀, conformal index (COIN), and D₂cm3 for rectum, bladder and the sigmoid colon.
Manual optimization led to a mean target coverage of 78.3% compared to 87.5%, 91.7% and 82.5% with the three IPSA approaches (p < 0.001). Similar COIN values for manual and inverse optimization were found. The manual optimization led to better results with respect to the dose to the OARs expressed as D₂cm3. Overall, the best results were obtained with manual optimization and IPSA plans with volumetric constraints including maximum doses to the target volume.
Dosimetric evaluation of manual and inverse optimization approaches is indicating the potential of IPSA for brachytherapy of cervical cancer. IPSA with constraints of maximum doses to the target volume is closer related to manual optimization than plans with constraints only to minimum dose to the target volume and maximum doses to OARs. IPSA plans with proper constraints performed better than those based on dose to target surface points and manually optimized plans.
比较五种逆向治疗计划方法与传统手动优化计划方法在宫颈癌近距离治疗剂量学参数方面的差异。
本研究纳入了18例接受磁共振成像（MRI）引导的高剂量率（HDR）近距离治疗的宫颈癌患者。为每位患者的4次HDR近距离治疗分次中的每一次创建6个计划：1个手动优化计划和5个逆向计划。其中3个基于逆向计划模拟退火（IPSA），分别对靶区最大剂量有或无额外约束，对危及器官（OAR）剂量有不同约束。此外，还有2个基于靶区表面点剂量的计划。通过量化特定剂量学参数，如临床靶区体积（CTV）的D₉₀、CTV的D₁₀₀、适形指数（COIN）以及直肠、膀胱和乙状结肠的D₂cm3，从剂量学角度对所得剂量体积直方图进行分析和比较。
手动优化导致平均靶区覆盖率为78.3%，而三种IPSA方法分别为87.5%、91.7%和82.5%（p < 0.001）。手动优化和逆向优化的COIN值相似。在以D₂cm3表示的OAR剂量方面，手动优化取得了更好的结果。总体而言，手动优化以及对靶区体积包括最大剂量有体积约束的IPSA计划取得了最佳结果。
手动优化和逆向优化方法的剂量学评估表明IPSA在宫颈癌近距离治疗中的潜力。对靶区最大剂量有约束的IPSA比仅对靶区最小剂量和OAR最大剂量有约束的计划更接近手动优化。具有适当约束的IPSA计划比基于靶区表面点剂量的计划和手动优化计划表现更好。
