Comparative Analysis of Dynamic Conformal Arc Therapy and Volumetric-modulated Arc Therapy in Lung Stereotactic Body Radiation Therapy: Evaluating Dosimetric Performance, Treatment Delivery Efficiency, and Plan Robustness

Abstract

Background/aim: This study evaluated and compared dynamic conformal arc therapy (DCAT) and volumetric-modulated arc therapy (VMAT) in stereotactic body radiation therapy (SBRT) for peripheral lung tumors, focusing on dosimetric outcomes, treatment delivery efficiency, and plan robustness against multileaf collimator (MLC) positional errors.

Patients and methods: Thirty patients with peripheral lung tumors who underwent SBRT during the study period were included. All treatment plans were generated using the Monaco treatment planning system and delivered via a Versa HD linear accelerator. Dosimetric parameters - including target coverage, organ-at-risk (OAR) sparing, and plan complexity - were evaluated based on Radiation Therapy Oncology Group (RTOG) guidelines. The effect of MLC leaf positional errors on the dose distribution was systematically simulated and analyzed using a generalized equivalent uniform dose (gEUD).

Results: DCAT demonstrated significantly lower D98%, D50%, Dmax, and homogeneity index, along with a higher conformity index than VMAT; however, all were within clinically acceptable ranges. The DCAT plans exhibited significantly lower plan complexity, fewer monitor units, and shorter delivery times compared to VMAT. Additionally, DCAT showed superior robustness to systematic MLC leaf opening and closing errors, with smaller dose deviations in both the planning target volume and OARs. No significant differences were observed between DCAT and VMAT in shift and random MLC errors.

Conclusion: DCAT demonstrated clinically acceptable dosimetric results comparable to those of VMAT for lung tumor SBRT, while offering superior treatment efficiency and robustness to MLC positional errors. These findings suggested that DCAT is an effective alternative to VMAT in clinical practice.

Keywords: MLC positional error; Stereotactic body radiation therapy (SBRT); dynamic conformal arc therapy (DCAT); lung cancer; plan robustness; volumetric modulated arc therapy (VMAT).