A Dosimetric Comparison of Volumetric-modulated Arc Therapy and IMRT for Cochlea-sparing Radiation Therapy in Locally Advanced Nasopharyngeal Cancer

Abstract

Background: Head-and-neck cancer treatment includes radiotherapy as a crucial component. However, radiotherapy, like other treatment modalities, has its own side effects, some of which can be avoided using the latest medical technology and understanding the illness. Despite being a relatively uncommon subtype of head-and-neck cancer, radiation is essential in the treatment of nasopharyngeal carcinoma (NPC). Because of the complex anatomy of the nasopharyngeal region, it is difficult to plan radiotherapy without sparing the cochlea, an important part of the auditory system, and the radiotherapy dosage to it may cause sensorineural hearing loss. In the modern era, volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) have become the gold standard in radiotherapy. With the advancement of these techniques, cochlear sparing is now possible without compromising the tumor dose.

Materials and methods: We reviewed 14 plans for patients with locally advanced NPC who had received radiation in our department. VMAT plans were created for patients who had IMRT radiotherapy and vice versa. Both approaches were evaluated in terms of cochlea sparing while maintaining the coverage of the planned target volume (PTV).

Results: Our study compared the results of two different radiation techniques for locally advanced NPC, IMRT, and VMAT in 14 cases, and we found that VMAT was associated with a lower maximum dose to the cochlea, a lower mean dose to the cochlea, a higher PTV D98% (Gy), a lower PTV D2% (Gy), a higher PTV V95% (%), a lower heterogeneity index, and a higher conformity index. The P value for each comparison was <0.05, which indicates that the difference is statistically significant. These results suggest that VMAT is a better radiation technique than IMRT for locally advanced NPC. VMAT is associated with a lower dose to the cochlea and other organs at risk, which can improve the quality of life and survival of patients.

Conclusion: These results suggest that VMAT is a better radiation technique than IMRT for locally advanced NPC. VMAT is associated with a lower dose to the cochlea and other organs at risk, which can improve the quality of life and survival of patients.

Keywords: Cochlea; intensity-modulated radiotherapy; nasopharyngeal cancer; radiotherapy; volumetric-modulated arc therapy.

Figure 1

Dose distribution on axial computed tomography image: (a) IMRT plan, (b) Volumetric-modulated arc therapy plan. IMRT: Intensity modulated radiotherapy