Assessment of the therapeutic accuracy of cone beam computed tomography‑guided nasopharyngeal carcinoma radiotherapy

Abstract

The aim of the present study was to determine the ability of cone beam computed tomography (CBCT) to improve the accuracy of nasopharyngeal carcinoma (NPC) radiotherapy by analyzing the setup and inter-fraction errors at different levels and directions of the target volumes. A total of 113 patients with NPC who were undergoing intensity-modulated radiotherapy were recruited for the present study. Each patient had at least three CBCT exams prior to the start of radiation therapy. Three anatomic bony landmarks, including the upper neck, lower neck and head, were used to represent the different levels of assessment. The positioning errors were registered in three planes throughout the course of radiotherapy: The right-left (RL), superior-inferior (SI) and anterior-posterior (AP) directions. The planning CT images were matched with the CBCT images to determine the naso-pharynx shifts. A receiver operating characteristic curve was plotted to establish the specificity and sensitivity of CBCT. The planning target volume margin (MPTV) for the head was 0.9 mm, 1.4 mm for the upper neck and 2.0 mm for the lower neck. MPTVs of 1.5, 0.6 and 2.2 mm in the RL, SI and AP directions, respectively, were detected. In addition, there was evidence of setup errors in the three planes (RL, SI and AP) with the greatest error observed in the AP direction. Furthermore, the setup uncertainties in the neck region were greater than those of the head. In conclusion, CBCT could greatly improve the accuracy of radiotherapy by minimizing the setup errors and MPTV.

Effect of Body Size Change on Off-Center Cervical Point and Face Doses in Patients Undergoing Nasopharyngeal Carcinoma Radiotherapy

“…However, IMRT still has some limitations such as its precise dose distribution of target region sketch has strict requirements. Moreover, several local and international studies have pointed out that in the process of radiation therapy, the weight loss in patients with NPC allows lymph nodes to disappear, and the initial tumor shrinkage factors may lead to a target area and endanger the organs (especially the spinal cord, brain stem, parotid gland), resulting in a change in anatomical position and actual exposure dose [ 16 , 17 ].…”

Chemotherapy in Combination With Radiotherapy for Definitive-Intent Treatment of Stage II-IVA Nasopharyngeal Carcinoma: CSCO and ASCO Guideline

“…Daily image guidance may also enable customized margin for planning target volumes (PTV) and monitoring of geometric and dosimetric changes during the planned course of RT. [114][115][116][117][118] IMRT can be delivered using either sequential boost or simultaneous integrated boost technique. A phase III RCT 57 of 209 patients has shown similar efficacy and toxicities with these two approaches.…”

Two-dimensional and Three-dimensional Image-guided Evaluation of Patient Positioning for Intensity-modulated Radiation Therapy of Head and Neck Cancer

“…The result showed that the mean couch displacement was small in both image-guided techniques and similar to other studies (Table 4). One study by Djordjevic et al [10] evaluated the set-up error in 80 HNC patients using daily OBI and reported that the mean couch displacement was -0.05 cm A-P, -0.06 cm S-I, and -0.06 cm L-R. Another study by Liu et al [19] evaluated the daily set-up error in 120 HNC patients (NPC) using CBCT and reported that the mean couch displacement in A-P, S-I, and L-R directions was 0.19 cm, 0.13 cm, and 0.15 cm, respectively. However, other studies have reported a more significant mean couch displacement with CBCT.…”