Comparison of Survival Outcomes and Toxicities Between Volumetric-modulated Arc Therapy and Conventional Radiotherapy in Early Glottic Cancer.

BACKGROUND/AIM: To compare survival outcomes and radiation-related toxicities between conventional radiotherapy (CvT) and volumetric-modulated arc therapy (VMAT) in patients with early glottic cancer.

PATIENTS AND METHODS: We reviewed 81 patients with Tis-T2N0 glottic cancer who underwent definitive radiotherapy between 2010 and 2018. CvT (N=47) was delivered using two opposing lateral beams (70 Gy in 35 fractions), while VMAT (N=34) utilized two arcs (65.25 Gy in 29 fractions). Hypothyroidism was defined as an elevated thyroid-stimulating hormone level with or without a decrease in free T4 or T3 levels.

RESULTS: The overall median follow-up time was 80.0 months and was longer in the CvT group (116.0 months) than in the VMAT group (45.3 months). Five-year local failure-free survival (95.4% vs. 84.5%, p=0.088), regional failure-free survival (93.0% vs. 94.1%, p=0.481), locoregional failure-free survival (90.9% vs. 84.7%, p=0.319), and overall survival (89.4% vs. 90.7%, p=0.575) were comparable between the CvT and VMAT groups, respectively. No increase in regional failure was observed in the VMAT group despite exclusion of the anterior level III neck. Most local failures in the VMAT group occurred near the original tumor site and were associated with T2 disease (p=0.015). Hypothyroidism occurred more frequently in the CvT group (53.5%) than in the VMAT group (25.9%, p=0.043). Carotid artery events were noted in three patients treated with CvT (6.4%), with none in the VMAT group.

CONCLUSION: VMAT demonstrated comparable survival outcomes to CvT while significantly reducing the incidence of hypothyroidism and potentially lowering carotid artery events. VMAT may be considered a preferred modality to improve quality of life in patients with early glottic cancer.