放射線外科技術（SRS）と全脳照射（WBRT）による脳体積減少のAIベース評価

Radiotherapy is a cornerstone in the treatment of brain metastases, but its mid- and long-term impact on brain parenchyma remains poorly understood. This study aimed to assess the differential volumetric alterations in the brain following two different modalities of Radiotherapy-Stereotactic Radiosurgery (SRS) and Whole-Brain Radiotherapy (WBRT).

Patients treated with SRS were drawn from the prospective dataset of the STEREOBRAIN study (DRKS00014694) that recruited patients with 4-10 brain metastases from 2017 to 2020. Patients that had received WBRT for the treatment of 4-10 brain metastases from 2012 to 2017 were included retrospectively. Patients with clinical and radiographic signs of hydrocephalus were excluded. Volumetric analysis of CSF space was implemented as a measure of brain volume decrease. Images were registered to MNI305 space and segmented by a pretrained UNesT artificial network.

Overall, 59 patients were included. 29 patients received SRS and 30 WBRT respectively. The ventricular system volume increased significantly in both SRS (p-value 0.014) and WBRT (p-value < 0.0001) groups. In the WBRT group, ventricular enlargement was more pronounced, both in absolute and ventricle-brain-ratio terms (p-value < 0.0001). WBRT was associated with significantly larger increases in ventricular volume than SRS, both in absolute (p = 0.0127) and relative (p = 0.0017) terms.

Radiotherapy is associated with a decrease in brain volume, which seems be less pronounced in patients treated with SRS as compared to WBRT. The clinical implication of this finding, e.g., the impact of brain volume decrease on overall-survival and neuro-cognitive function, is yet to be determined.