Program Information
Dosimetric Changes of Brainstem Caused by Weight Loss During Intensity-Modulated Radiation Therapy for Nasopharyngeal Carcinoma
W Hu*, C Yu , Y Cai , X Zhou , W Wang , H Yang , Affiliated Taizhou hospital of Wenzhou Medical University, Taizhou, Zhejiang
Presentations
SU-F-P-25 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:To explore dosimetric effects of brainstem (BS) caused by weight loss during the course of intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC).
Methods:Seventy-seven patients who were diagnosed with NPC by pathology biopsy have been enrolled. Every patients should receive weight measurement weekly and three times of computed tomography (CT) scans and replanning, at the 15th and 25th fraction during the treatment, respectively. The vertical diameter at the level of odontoid process (d1) and cervical vertebra 3 (d2) be measured from CT images(Supporting document Figure 1). All IMRT plans were designed by inverse planning with commercial treatment planning systems (Corvus 6.2 version, NOMOS Corporation). The dose differences between plan and actual delivery were generated to compare.
Results:The weight loss was more in week 4-5 (3.21±2.19kg) than in week 1-3 (1.79±1.83kg)(Supporting document Figure 2). The d1 and d2 decreased was more significantly in week 4-5 than week 1-3, 2.83±1.75mm vs. 0.55±0.75mm and 2.98±2.96mm vs. 1.23±2.09mm, respectively. The maximum dose to the brainstem (BS Dmax) and the percentage of brainstem volume receiving ≥50Gy (BS V50) increased more significantly in week 4-5 than week 1-3, -3.02±5.49Gy vs. -1.85 ±4.88Gy and -1.85±4.88% vs. -0.77±3.32%, respectively. The changes of d1 and d2 and the BS-V50 and BS-Dmax were closely related to weight loss (p≤0.001)(Supporting document Table 1).
Conclusion:The study results indicate that weight loss leads to the vertical diameter reduction, which results has a close relationship with dose of the brainstem during IMRT of NPC.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by Zhejiang Provincial Medicine and Health Foundation (2013KYB290) and Research Foundation of Science and Technology Department of Zhejiang Province 2015C33257
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