Changes of the transverse diameter and volume and dosimetry before the 25th fraction during the course of intensity-modulated radiation therapy (IMRT) for patients with nasopharyngeal carcinoma
- 作者：Haihua Yang ; M.D. ; Wei Hu ; M.D. ; huw@tzhospital.com ; Weijun Ding ; M.D. ; Guoping Shan ; B.S. ; Wei Wang ; B.S. ; Changhui Yu ; B.S. ; Biyun Wang ; M.D. ; Minghai Shao ; M.D. ; Jianhua Wang ; M.D. ; Weifang Yang ; M.D.
- 关键词：Nasopharyngeal carcinoma ; Intensity-modulated radiotherapy ; Transverse diameter change ; Volume change ; Dosimetric change
- 刊名：Medical Dosimetry
- 出版年：2012
- 期刊代码：195_09583947
- 类别：med
- 出版时间：Summer, 2012
- 卷：37
- 期：2
- 页码：225-229
- 文件大小：1021 K
摘要
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 卤 4.45 mm, 6.80 卤 15.14 mm, 5.70 卤 6.26 mL, and 5.04 卤 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 卤 5.55 Gy, 7.18 卤 10.07%, 4.51 卤 8.55 Gy, 6.59 卤 17.82%, 5.33 卤 8.55 Gy, 11.68 卤 17.11%and 1.48 卤 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.