Frameless high dose rate stereotactic lung radiotherapy: Intrafraction tumor position and delivery time

Intrafraction change in tumor position (Δ) was evaluated for stereotactic lung radiotherapy delivered with flattening filter free volumetric modulated arc therapy. In 140 fractions from 32 patients mean Δ (±SD) was −0.7 ± 1.4 mm (vertical), −0.7 ± 1.3 mm (longitudinal) and +0.2 ± 1.2 mm (lateral) with mean vector 2.1 ± 1.2 mm. Mean delivery time was 4.4 ± 3.4 min (mean beam-on 1.9 ± 0.4 min).