Anatomic and Dosimetric Changes During the Treatment Course of Intensity-Modulated Radiotherapy for Locally Advanced Nasopharyngeal Carcinoma
- Department of Radiation Oncology, Cancer Hospital, Shanghai Medical College, Fudan University, Shanghai (China)
Many patients with nasopharyngeal carcinoma (NPC) have marked anatomic change during intensity-modulated radiation therapy (IMRT). In this study, the magnitude of anatomic changes and its dosimetric effects were quantified. Fifteen patients with locally advanced NPC treated with IMRT had repeated computed tomography (CT) after 18 fractions. A hybrid plan was made to the anatomy of the second computed tomography scan. The dose of the original plan, hybrid plan, and new plan were compared. The mean volume of left and right parotid decreased 6.19 mL and 6.44 mL, respectively. The transverse diameters of the upper bound of odontoid process, the center of odontoid process, and the center of C2 vertebral body slices contracted with the mean contraction of 8.2 mm, 9.4 mm, and 7.6 mm. Comparing the hybrid plan with the treatment plan, the coverage of target was maintained while the maximum dose to the brain stem and spinal cord increased by 0.08 to 6.51 Gy and 0.05 to 7.8 Gy. The mean dose to left and right parotid increased by 2.97 Gy and 2.57 Gy, respectively. A new plan reduced the dose of spinal cord, brain stem, and parotids. Measurable anatomic changes occurring during the IMRT for locally advanced NPC maintained the coverage of targets but increased the dose to critical organs. Those patients might benefit from replanning.
- OSTI ID:
- 21333983
- Journal Information:
- Medical Dosimetry, Vol. 35, Issue 2; Other Information: DOI: 10.1016/j.meddos.2009.06.007; PII: S0958-3947(09)00058-2; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0958-3947
- Country of Publication:
- United States
- Language:
- English
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