Three-Phase Adaptive Radiation Therapy for Patients With Nasopharyngeal Carcinoma Undergoing Intensity-Modulated Radiation Therapy: Dosimetric Analysis

Abstract

Patients with nasopharyngeal carcinoma undergoing intensity-modulated radiation therapy may experience significant anatomic changes throughout the entire treatment course, and adaptive radiation therapy may be necessary to maintain optimal dose delivered both to the targets and to the critical structures. The timing of adaptive radiation therapy, however, is largely unknown. This study was to evaluate the dosimetric benefits of a 3-phase adaptive radiation therapy technique for nasopharyngeal carcinoma. Twenty patients with nasopharyngeal carcinoma treated with intensity-modulated radiation therapy were recruited prospectively. After fractions 5 and 15, each patient had repeat computed tomography scans, and adaptive replans with recontouring the targets and organs at risk on the new computed tomography images were generated and used for subsequent treatment (replan 1 and replan 2). Two hybrid intensity-modulated radiation therapy plans (plan 1 and plan 2) were generated by superimposing the initial plan (plan 0) to each repeated new computed tomography image, reflecting the actual dose delivered to the targets and organs at risk if no changes were made to the original plan. Dosimetric comparisons were made between the adaptive replans (adaptive radiation therapy plans: plan 0 + replan 1 + replan 2) and their corresponding nonadaptive radiation therapy plans (plan 0 + plan 1 + plan 2). Comparing with the nonadaptive radiation therapy plans, the adaptive radiation therapy plans resulted in a significant improvement in conformity index for planning target volumes for primary disease, involved lymph node, high-risk clinical target volume, and low-risk clinical target volume (PTVnx, PTVnd, PTV1, and PTV2, respectively). Median V95 for PTVnx; D95, D99, V100, V95, and V93 for PTVnd; D99 and V100 for PTV1; and D95, D99, V100, V95, and V93 for PTV2 were increased significantly. There were significant dose–volume reductions, including maximum doses to the brainstem and temporal lobes, mean doses to the glottis, V50 for the supraglottis, Dmean and V30 for the left parotid, median dose to the right optic nerve, and V55 for the skin. The 3-phase adaptive intensity-modulated radiation therapy for patients with nasopharyngeal carcinoma results in improvements in target coverage and conformity index and decreased doses to some organs at risk.

Study of the dose-volume parameters variation in tumor target volumes and organs at risk during nasopharyngeal carcinoma radiotherapy applying deformation registration

“…In the process of IMRT, although IMRT is more effective than conventional radiotherapy in increasing the target dose, the radiation exposure of normal tissues and OARs is relatively low ( 9 , 10 ). However, for NPC, factors such as changes in the patient weight, volume of tumors and OARs may have a certain impact on dose assessment.…”

Multi-Organ Omics-Based Prediction for Adaptive Radiation Therapy Eligibility in Nasopharyngeal Carcinoma Patients Undergoing Concurrent Chemoradiotherapy

“…Confronted with this, Adaptive Radiotherapy (ART), a modification of the original treatment plan, has been introduced to compensate for these patient-specific variations. The dosimetric and clinical benefits of ART for NPC patients have been well-documented in the literature (1)(2)(3)(4)(5)(6)(7).…”

A Multi-Center Study of CT-Based Neck Nodal Radiomics for Predicting an Adaptive Radiotherapy Trigger of Ill-Fitted Thermoplastic Masks in Patients with Nasopharyngeal Carcinoma

“…However, anatomic variations and body weight loss of NPC patients are not uncommon [7][8][9][10][11][12][13], posing a risk of TM unfit. In cases of ill-fitted TMs (IfTMs), an ad hoc adaptive radiotherapy (ART) may be triggered to ensure accuracy and safe radiation delivery and to maintain treatment efficacy [14][15][16][17]. Presently, clinical ART practice is still in its infant stage.…”