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

Journal Article · Sun Jul 01 04:00:00 EDT 2012 · Medical Dosimetry

DOI:https://doi.org/10.1016/J.MEDDOS.2011.08.003· OSTI ID:22130409

Haihua, Yang ^[1]; Weijun, Ding; Guoping, Shan; Wei, Wang; Changhui, Yu; Biyun, Wang; Minghai, Shao; Jianhua, Wang; Weifang, Yang ^[1]

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1. Department of Radiation Oncology, Taizhou Hospital, Wenzhou Medical College, Taizhou, Zhejiang (China)

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.

• OSTI ID: 22130409
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 2 Vol. 37; ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
BRAIN
CARCINOMAS
CAT SCANNING
DOSIMETRY
GLANDS
NECK
PATIENTS
PHANTOMS
RADIATION DOSES
RADIOTHERAPY
SIMULATION
SPINAL CORD