Toward optimal radiotherapy in tongue cancer: a comparative study of IMRT and VMAT.

Abstract

This retrospective study compared the dosimetric performance of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in patients with T3N2 stage squamous cell carcinoma of the tongue treated in a post-operative setting. Thirty patients received 60 Gy in 30 fractions. IMRT plans were developed and corresponding VMAT plans were generated in the Monaco treatment planning system with identical target coverage and organ-at-risk (OAR) constraints using the Monte Carlo algorithm (3 mm grid, 2% statistical uncertainty). Dose-volume parameters for the planning target volume (PTV) and plan quality indices including conformity index (CI), homogeneity index (HI), and uniformity index (UI) were evaluated alongside OAR doses. Both IMRT and VMAT achieved clinically acceptable and comparable target coverage. The small numerical differences observed in PTV dosimetric parameters and plan quality indices between the two techniques should be interpreted with caution, as they fall within the range of the 2% Monte Carlo statistical uncertainty used in dose calculation. OAR doses were broadly similar between techniques, with IMRT demonstrating marginally lower doses to certain serial structures including the spinal cord and brainstem, though all values remained well within established tolerance limits for both techniques. The primary clinically meaningful advantage of VMAT was improved delivery efficiency, demonstrated by reduced monitor units (1033.9 vs. 1212.89) and shorter treatment time (approximately 5 min vs. 8 min). For T3N2 post-operative tongue carcinoma, both IMRT and VMAT provide clinically equivalent dosimetric plan quality, with VMAT offering a significant advantage in treatment delivery efficiency.