title: Volume and dosimetric variations during two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal carcinoma.
abstract: The aims of this study were to evaluate the volume and dosimetric variations during IMRT for locally advanced NPC and to identify the benefits of a two-phase adaptive IMRT method. Twenty patients with locally advanced NPC having received IMRT treatment were included. Each patient had both an initial planning CT (CT-1) and a repeated CT scan (CT-2) after treatment at a dose of 40 Gy. Three IMRT planning scenarios were compared: (1) the initial plan on the CT-1 (plan-1); (2) the hybrid plan recalculated the initial plan on the CT-2 (plan-2); (3) the replan generated on the CT-2 being used to complete the course of IMRT (plan-3). The mean gross target volume and mean volumes of the positive neck lymph nodes, high-risk clinical target volume, and the left and right parotid glands significantly decreased by 30.2%, 45.1%, 21.1%, 14.7% and 18.2%, respectively on the CT-2. Comparing plan-2 with plan-1, the dose coverage of the targets remained unchanged, whereas the dose delivered to the parotid glands and spinal cord increased significantly. These patients with locally advanced NPC might benefit from replanning because of the sparing of the parotid glands and spinal cord.
authors.affiliation: Radiotherapy Center, Affiliated Tumor Hospital of Guangzhou Medical University, Guangzhou, China.
authors.forename: Rui-hao
authors.initials: RH
authors.lastname: Wang
authors.forename: Shu-xu
authors.initials: SX
authors.lastname: Zhang
authors.forename: Ling-hong
authors.initials: LH
authors.lastname: Zhou
authors.forename: Guo-qian
authors.initials: GQ
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Yu
authors.forename: Xiao-dan
authors.initials: XD
authors.lastname: Lin
authors.forename: Shengqu
authors.initials: S
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D013116:Spinal Cord / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Nasopharyngeal carcinoma; adaptive replanning; anatomic changes; intensity-modulated radiotherapy