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
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- 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
- 出版时间：Summer, 2012
- 年：2012
- 卷：37
- 期：2
- 页码：225-229
- 全文大小：1021 K
文摘
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 ¡À 4.45 mm, 6.80 ¡À 15.14 mm, 5.70 ¡À 6.26 mL, and 5.04 ¡À 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 ¡À 5.55 Gy, 7.18 ¡À 10.07 % , 4.51 ¡À 8.55 Gy, 6.59 ¡À 17.82 % , 5.33 ¡À 8.55 Gy, 11.68 ¡À 17.11 % and 1.48 ¡À 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.