Abstract
Previous studies on advanced radiotherapy (RT) techniques for early stage glottic cancer have focused on sparing the carotid artery. However, the aim of the present study was to evaluate the dosimetric advantages of volumetric modulated arc therapy (VMAT) in terms of sparing the thyroid gland in early-stage glottic cancer patients. In total, 15 cT1N0M0 glottic cancer patients treated with definitive RT using VMAT were selected, and for dosimetric comparison, a conventional RT plan comprising opposed-lateral wedged fields was generated for each patient. The carotid artery, thyroid gland and spinal cord were considered organs at risk. The prescription dose was 63 Gy at 2.25 Gy per fraction. For the thyroid gland and carotid artery, all compared parameters were significantly lower with VMAT compared with conventional RT. For the thyroid gland, the median reduction rates of the mean dose (Dmean), the volume receiving ≥30% of the prescription dose (V30) and the V50 were 32.6, 40.9 and 46.0%, respectively. The Dmean was 14.7±2.6 Gy when using VMAT compared with 22.2±3.9 Gy when using conventional RT. The differences between the techniques in terms of planning target volume coverage and dose homogeneity were not significant. When considering a recent normal tissue complication probability model, which indicated the mean thyroid gland dose as the most significant predictor of radiation-induced hypothyroidism, the dosimetric advantage shown in this study may be valuable in reducing hypothyroidism following RT for early stage glottic cancer patients.
Highlights
For early‐stage (T1‐2N0M0) glottic cancer, radiotherapy (RT) and surgery have been demonstrated to yield significant localKey words: carotid artery, early stage, glottic cancer, thyroid gland, volumetric modulated arc therapy disease control; >90% for T1 and 80% for T2
The partial volume effects between the thyroid gland and hypothyroidism were unclear in the study by Emami et al [18], which was based on a simple consensus of clinical experience or opinions, with little high‐quality clinical data
A normal tissue complication probability (NTCP) model of radiation‐induced hypothyroidism has been developed based on a prospective multivariate analysis [20]
Summary
For early‐stage (T1‐2N0M0) glottic cancer, radiotherapy (RT) and surgery have been demonstrated to yield significant local. Such favorable outcomes of RT have been achieved using simple RT techniques of parallel‐opposed lateral beams with wedges or tissue compensators [2]. Advanced RT techniques, including intensity‐modulated RT (IMRT) and volumetric modulated arc therapy (VMAT), have been adopted rapidly for various head and neck cancers. RT techniques used for early‐stage glottic cancer have not changed considerably, possibly since the target volume is relatively small and involves no elective nodal irradiation, with low rates of severe toxicity [2,3]. One previous study questioned the role of IMRT in early‐stage glottic cancer [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
