Abstract:
Objective This study compares volumetric-modulated arc therapy(RapidArc) and fixed field intensity-modulated radiation therapy(IMRT) for advanced nasopharyngeal carcinoma.
Methods Ten advanced nasopharyngeal carcinoma patients were randomly selected for this study.Two treatment plans were completed for each patient, i.e., the RapidArc and IMRT schemes.Dosimetric verification was conducted for each scheme.The doses for the planning target volumes(PTVs), organs at risk(OARs), and normal tissues were compared.The technical delivery parameters, including monitor units(MUs), time of therapy, and results of dosimetric verification, were analyzed.
Results No significant differences were found in dose distribution between the two schemes.Both techniques delivered adequate doses for the PTVs.For RapidArc planning, the minimal dose of PTVnx, mean dose of PTVnd, PTV60, larynx, and parotid were lower compared with those of IMRT schemes, whereas the homogeneity index of PTV60 was higher.Compared with IMRT plans, the MUs and treatment time in RapidArc plans were reduced by approximately 58% and 70%, respectively.Gamma analysis produced an average pass rate of 98.75%± 0.50% and 98.86%±0.67% at the 3%/3 mm levels for RapidArc and IMRT, respectively.
Conclusion Both RapidArc and IMRT plans satisfied the requirements for advanced nasopharyngeal carcinoma therapy.The dose measurements showed good agreement with the computed doses.The RapidArc technique has much more superiority compared with the IMRT technique.The former decreases not only the MUs and treatment time, but also the dose to the larynx and parotid glands.