Pedicini Piernicola, Strigari Lidia, Benassi Marcello, Caivano Rocchina, Fiorentino Alba, Nappi Antonio, Salvatore Marco, Storto Giovanni
Service of Medical Physics, I.R.C.C.S. Regional Cancer Hospital C.R.O.B, Rionero in Vulture, Italy.
Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy.
Med Dosim. 2014 Spring;39(1):23-30. doi: 10.1016/j.meddos.2013.08.009. Epub 2013 Nov 13.
To increase the efficacy of radiotherapy for non-small cell lung cancer (NSCLC), many schemes of dose fractionation were assessed by a new "toxicity index" (I), which allows one to choose the fractionation schedules that produce less toxic treatments. Thirty-two patients affected by non resectable NSCLC were treated by standard 3-dimensional conformal radiotherapy (3DCRT) with a strategy of limited treated volume. Computed tomography datasets were employed to re plan by simultaneous integrated boost intensity-modulated radiotherapy (IMRT). The dose distributions from plans were used to test various schemes of dose fractionation, in 3DCRT as well as in IMRT, by transforming the dose-volume histogram (DVH) into a biological equivalent DVH (BDVH) and by varying the overall treatment time. The BDVHs were obtained through the toxicity index, which was defined for each of the organs at risk (OAR) by a linear quadratic model keeping an equivalent radiobiological effect on the target volume. The less toxic fractionation consisted in a severe/moderate hyper fractionation for the volume including the primary tumor and lymph nodes, followed by a hypofractionation for the reduced volume of the primary tumor. The 3DCRT and IMRT resulted, respectively, in 4.7% and 4.3% of dose sparing for the spinal cord, without significant changes for the combined-lungs toxicity (p < 0.001). Schedules with reduced overall treatment time (accelerated fractionations) led to a 12.5% dose sparing for the spinal cord (7.5% in IMRT), 8.3% dose sparing for V20 in the combined lungs (5.5% in IMRT), and also significant dose sparing for all the other OARs (p < 0.001). The toxicity index allows to choose fractionation schedules with reduced toxicity for all the OARs and equivalent radiobiological effect for the tumor in 3DCRT, as well as in IMRT, treatments of NSCLC.
为提高非小细胞肺癌（NSCLC）放疗的疗效，通过一种新的“毒性指数”（I）评估了多种剂量分割方案，该指数能让人选择产生毒性较小治疗效果的分割方案。32例不可切除的NSCLC患者采用标准三维适形放疗（3DCRT）治疗，采用限制治疗体积的策略。利用计算机断层扫描数据集通过同步整合加量调强放疗（IMRT）重新计划。通过将剂量体积直方图（DVH）转换为生物等效DVH（BDVH）并改变总治疗时间，使用计划中的剂量分布来测试3DCRT以及IMRT中的各种剂量分割方案。通过毒性指数获得BDVH，该指数通过线性二次模型为每个危及器官（OAR）定义，对靶体积保持等效的放射生物学效应。毒性较小的分割方案包括对包括原发肿瘤和淋巴结的体积进行重度/中度超分割，随后对缩小的原发肿瘤体积进行低分割。3DCRT和IMRT分别使脊髓的剂量节省了4.7%和4.3%，联合肺毒性无显著变化（p<0.001）。总治疗时间缩短的方案（加速分割）使脊髓的剂量节省了12.5%（IMRT中为7.5%），联合肺中V20的剂量节省了8.3%（IMRT中为5.5%），并且对所有其他OAR也有显著的剂量节省（p<0.001）。毒性指数允许在NSCLC的3DCRT以及IMRT治疗中选择对所有OAR毒性降低且对肿瘤具有等效放射生物学效应的分割方案。
