Polgár C, Major T, Somogyi A, Takácsi-Nagy Z, Mangel L C, Forrai G, Sulyok Z, Fodor J, Németh G
National Institute of Oncology, Department of Radiotherapy, Budapest, Hungary.
Strahlenther Onkol. 2000 Mar;176(3):118-24. doi: 10.1007/pl00002336.
To compare the conventional 2-D, the simulator-guided semi-3-D and the recently developed CT-guided 3-D brachytherapy treatment planning in the interstitial radiotherapy of breast cancer.
In 103 patients with T1-2, N0-1 breast cancer the tumor bed was clipped during breast conserving surgery. Fifty-two of them received boost brachytherapy after 46 to 50 Gy teletherapy and 51 patients were treated with brachytherapy alone via flexible implant tubes. Single, double and triple plane implant was used in 6, 89 and 8 cases, respectively. The dose of boost brachytherapy and sole brachytherapy prescribed to dose reference points was 3 times 4.75 Gy and 7 times 5.2 Gy, respectively. The positions of dose reference points varied according to the level (2-D, semi-3-D and 3-D) of treatment planning performed. The treatment planning was based on the 3-D reconstruction of the surgical clips, implant tubes and skin points. In all cases the implantations were planned with a semi-3-D technique aided by simulator. In 10 cases a recently developed CT-guided 3-D planning system was used. The semi-3-D and 3-D treatment plans were compared to hypothetical 2-D plans using dose-volume histograms and dose non-uniformity ratios. The values of mean central dose, mean skin dose, minimal clip dose, proportion of underdosaged clips and mean target surface dose were evaluated. The accuracy of tumor bed localization and the conformity of planning target volume and treated volume were also analyzed in each technique.
With the help of conformal semi-3-D and 3-D brachytherapy planning we could define reference dose points, active source positions and dwell times individually. This technique decreased the mean skin dose with 22.2% and reduced the possibility of geographical miss. We could achieve the best conformity between the planning target volume and the treated volume with the CT-image based 3-D treatment planning, at the cost of worse dose homogeneity. The mean treated volume was reduced by 25.1% with semi-3-D planning, however, it was increased by 16.2% with 3-D planning, compared to the 2-D planning.
The application of clips into the tumor bed and the conformal (semi-3-D and 3-D) planning help to avoid geographical miss. CT is suitable for 3-D brachytherapy planning. Better local control with less side effects might be achieved with these new techniques. Conformal 3-D brachytherapy calls for new treatment planning concepts, taking the irregular 3-D shape of the target volume into account. The routine clinical application of image-based 3-D brachytherapy is a real aim in the very close future.
比较传统二维、模拟机引导的半三维和最近开发的CT引导的三维近距离放射治疗计划在乳腺癌间质放疗中的应用。
103例T1-2、N0-1期乳腺癌患者在保乳手术期间对瘤床进行了标记。其中52例在接受46至50 Gy远距离放疗后接受了补充近距离放疗，51例患者通过可弯曲植入管单独接受近距离放疗。分别有6例、89例和8例采用单平面、双平面和三平面植入。补充近距离放疗和单纯近距离放疗规定的剂量参考点剂量分别为3次4.75 Gy和7次5.2 Gy。剂量参考点的位置根据所进行的治疗计划水平（二维、半三维和三维）而有所不同。治疗计划基于手术标记、植入管和皮肤点的三维重建。所有病例均采用模拟机辅助的半三维技术进行植入计划。10例采用了最近开发的CT引导三维计划系统。使用剂量体积直方图和剂量不均匀率将半三维和三维治疗计划与假设的二维计划进行比较。评估平均中心剂量、平均皮肤剂量、最小标记剂量、标记剂量不足的比例和平均靶表面剂量的值。还分析了每种技术中瘤床定位的准确性以及计划靶体积与治疗体积的适形性。
借助适形的半三维和三维近距离放疗计划，我们可以分别定义参考剂量点、放射源活性位置和驻留时间。该技术使平均皮肤剂量降低了22.2%，并降低了遗漏照射的可能性。基于CT图像的三维治疗计划能够实现计划靶体积与治疗体积之间的最佳适形性，但代价是剂量均匀性较差。与二维计划相比，半三维计划使平均治疗体积减少了25.1%，而三维计划使其增加了16.2%。
在瘤床中使用标记和适形（半三维和三维）计划有助于避免遗漏照射。CT适用于三维近距离放疗计划。这些新技术可能实现更好的局部控制且副作用更少。适形三维近距离放疗需要新的治疗计划概念，要考虑靶体积的不规则三维形状。基于图像的三维近距离放疗在不久的将来成为常规临床应用是一个切实的目标。
