Harmonization of dose prescription for lung stereotactic radiotherapy.

Background And Purpose: Pulmonary stereotactic treatments can be performed using dedicated linear accelerators as well as robotic-assisted units, and different strategies can be used for dose prescription. This study aimed to compare the doses received by the tumor with a gross tumor volume (GTV)-based prescription on D using a robotic-assisted unit () and planning target volume (PTV)-based prescription on D using a dedicated linac ().

Material & Methods: Plans of 32 patients were collected for , and a dose of 3 × 18 Gy was prescribed using type A algorithm and recalculated using a Monte-Carlo (MC) algorithm. The plans were normalized to match D with the mean of the cohort. The plans of 23 patients were collected for , and a dose of 3 × 18 Gy was prescribed to D using a MC algorithm. A 4D-sum method was developed to estimate doses for PTV and GTV. For validation, all plans were recalculated using an independent MC double-check software. A dose harmonization on D was determined for both methods.

Results: For , mean doses were D = 59.9 ± 2.1 Gy, D = 55.6 ± 1.2 Gy, D = 49.5 ± 0.0 Gy. For , the reported doses were D = 64.6 ± 2.1 Gy, D = 62.8 ± 1.7 Gy, and D = 60.0 ± 1.7 Gy. The dose trade-off of D = 55 Gy was obtained for both methods. For , it corresponded to a dose prescription of 3 × 20 Gy using type A algorithm, followed by rescaling to obtain D = 55 Gy. For , it corresponded to a dose prescription of D = 3 × 16.5 Gy using the MC algorithm.

Conclusions: This study determined similar near-minimum doses D of approximately 3 × 18.3 Gy (55 Gy) using a GTV-based prescription on a robotic-assisted unit () and a PTV-based prescription on a dedicated linac ().