Knocke T H, Pokrajac B, Fellner C, Pötter R
Universitätsklinik für Strahlentherapie und -biologie, Allgemeines Krankenhaus der Stadt Wien. strahlentherapie@univie_ac_at
Strahlenther Onkol. 1999 Feb;175(2):68-73. doi: 10.1007/BF02753845.
Using standardized simulator planning guided by bony landmarks for pelvic irradiation of primary cervical carcinoma with some patients a geographical miss regarding tumor or potential tumor spread can happen because of insufficient knowledge of the individual anatomical situation. The question arises whether for patients with this indication the higher effort in terms of time and personnel for 3D treatment planning is justified.
In a prospective study on 20 subsequent patients with primary cervical carcinoma in Stages I to III simulator planning of a 4-field box-technique was performed. After defining the planning target volume (PTV) in the 3D planning system the field configuration of the simulator planning was transmitted. The resulting plan was compared to a second one based on the defined PTV and evaluated regarding a possible geographical miss and encompassment of the PTV by the treated volume (ICRU). Volumes of open and shaped portals were calculated for both techniques.
Planning by simulation resulted in 1 geographical miss and in 10 more cases the encompassment of the PTV by the treated volume was inadequate. For a PTV of mean 1,729 cm3 the mean volume defined by simulation was 3,120 cm3 for the open portals and 2,702 cm3 for the shaped portals (Figure 1). The volume reduction by blocks was 13.4% (mean). With CT-based 3D treatment planning the volume of the open portals was 3.3% (mean) enlarged to 3,224 cm3 (Figure 2). The resulting mean volume of the shaped portals was 2,458 ccm. The reduction compared to the open portals was 23.8% (mean). The treated volumes were 244 cm3 or 9% (mean) smaller compared to simulator planning. The "treated volume/planning target volume ratio" was decreased from 1.59 to 1.42.
The introduction of 3D treatment planning for pelvic irradiation of cervical carcinoma is to be recommended for reasons of quality assurance. Reduction of the treated volume is possible but further research has to be done to determine whether the rate of complications can be decreased as well.
在以骨性标志为引导的标准化模拟定位计划用于原发性宫颈癌盆腔放疗时，由于对个体解剖情况了解不足，部分患者可能出现肿瘤或潜在肿瘤播散的摆位误差。对于有此适应证的患者，三维治疗计划在时间和人力方面付出更高的努力是否合理，这一问题由此产生。
对20例I至III期原发性宫颈癌患者进行前瞻性研究，采用四野盒式技术进行模拟定位计划。在三维计划系统中定义计划靶体积（PTV）后，传输模拟定位计划的射野配置。将所得计划与基于定义的PTV的第二个计划进行比较，并评估是否可能存在摆位误差以及治疗体积对PTV的包绕情况（国际辐射单位与测量委员会）。计算两种技术的开放野和成形野体积。
模拟定位计划导致1例摆位误差，另外10例中治疗体积对PTV的包绕不足。对于平均体积为1729 cm³的PTV，模拟定位计划定义的开放野平均体积为3120 cm³，成形野为2702 cm³（图1）。用铅挡块减少的体积平均为13.4%。基于CT的三维治疗计划中，开放野体积平均增大3.3%至3224 cm³（图2）。所得成形野平均体积为2458 ccm。与开放野相比减少了23.8%（平均）。与模拟定位计划相比，治疗体积小244 cm³或9%（平均）。“治疗体积/计划靶体积比”从1.59降至1.42。
出于质量保证的原因，推荐在宫颈癌盆腔放疗中引入三维治疗计划。治疗体积有可能减小，但还需进一步研究以确定并发症发生率是否也能降低。
