Yang Haihua, Hu Wei, Ding Weijun, Shan Guoping, Wang Wei, Yu Changhui, Wang Biyun, Shao Minghai, Wang Jianhua, Yang Weifang
Department of Radiation Oncology, Taizhou Hospital, Wenzhou Medical College, Taizhou, Zhejiang, China.
Med Dosim. 2012 Summer;37(2):225-9. doi: 10.1016/j.meddos.2011.08.003. Epub 2011 Dec 19.
To quantify changes of the transverse diameter and volume and dosimetry, and to illustrate the inferiority of non-replanning during intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) patients. Fifty-three NPC patients who received IMRT in 33 fractions were enrolled in this prospective trial. Before the 25th fraction, a new simulation computed tomography (CT) scan was acquired for all patients. The dose-volume histograms of the phantom plan were compared with the initial plan. Significant reduction of the transverse diameter of the nasopharyngeal, the neck, and 2 parotid glands volume was observed on second CT compared with the first CT (mean reduction 7.48 ± 4.45 mm, 6.80 ± 15.14 mm, 5.70 ± 6.26 mL, and 5.04 ± 5.85 mL, respectively; p < 0.01). The maximum dose and V-40 of the spinal cord, mean dose, and V30 of the left and right parotid, and V-50 of the brain stem were increased significantly in the phantom plan compared with the initial plan (mean increase 4.75 ± 5.55 Gy, 7.18 ± 10.07%, 4.51 ± 8.55 Gy, 6.59 ± 17.82%, 5.33 ± 8.55 Gy, 11.68 ± 17.11% and 1.48 ± 3.67%, respectively; p < 0.01). On the basis of dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 52.83% (28/53) of the phantom plans were out of limit compared with 1.89% (1/53) of the initial plans (p < 0.0001). Because of the significant change in anatomy and dose before the 25th fraction during IMRT, replanning should be necessary during IMRT with NPC.
为了量化鼻咽癌（NPC）患者在调强放射治疗（IMRT）过程中横径、体积和剂量测定的变化，并说明不重新计划的劣势。53例接受33次分割IMRT的NPC患者纳入了这项前瞻性试验。在第25次分割前，为所有患者进行了一次新的模拟计算机断层扫描（CT）。将体模计划的剂量体积直方图与初始计划进行比较。与第一次CT相比，第二次CT显示鼻咽、颈部和双侧腮腺体积的横径显著减小（平均减小分别为7.48±4.45mm、6.80±15.14mm、5.70±6.26mL和5.04±5.85mL；p<0.01）。与初始计划相比，体模计划中脊髓的最大剂量和V-40、左侧和右侧腮腺的平均剂量和V30以及脑干的V-50显著增加（平均增加分别为4.75±5.55Gy、7.18±10.07%、4.51±8.55Gy、6.59±17.82%、5.33±8.55Gy、11.68±17.11%和1.48±3.67%；p<0.01）。根据RTOG0225方案中的剂量约束标准，与初始计划的1.89%（1/53）相比，52.83%（28/53）的体模计划中正常关键结构的剂量超出了限值（p<0.0001）。由于IMRT过程中第25次分割前解剖结构和剂量的显著变化，NPC患者在IMRT期间进行重新计划是必要的。
