Multicenter evaluation of planning quality in intracranial stereotactic radiotherapy for brain metastases

Stereotactic radiotherapy (SRT) is a standard approach for treating multiple brain metastases. However, variation in planning practices may impact treatment quality. This study assessed planning consistency and dose-volume-based outcomes across radiation oncology centers.

A Computed Tomography (CT) scan of an anthropomorphic phantom with structure set was distributed to participating centers. Each center created SRT plans as for a clinical case. Dose distributions were evaluated based on Planning Target Volume (PTV) coverage (V₁₀₀% (PTV)), dose to 95% of Gross Target Volume (GTV) volume (D₉₅% (GTV)), maximal PTV dose (D_max), conformity index (CI), gradient index (GI), brain volume receiving different percentages of the prescribed dose, and doses delivered to 0.035 cm³ and 0.5 cm³ of the brainstem.

Twenty-four centers, using 30 treatment units, submitted plans. The V₁₀₀% (PTV) ranged from 95% to 100%, with D_max between 110% and 150% of the prescribed dose. Mean GTV dose ranged from 110% to 135%, and 81% of GTVs had D₉₅% between 110% and 120%. High conformity was achieved in 74% of plans (CI < 1.1), while 67% had a GI between 3.4 and 5. All plans met clinical dose constraints for the brainstem and uninvolved brain.

This interinstitutional comparison demonstrated high plan quality and adherence to critical organ constraints, despite variability in planning strategies. These findings support nationwide planning and quality assurance standards to ensure consistently high-quality SRT.