Perivascular spaces as MRI markers associated with radiation necrosis in brain metastases patients: an exploratory...

Radiation necrosis (RN) is a significant complication of stereotactic radiotherapy (SRT) for brain metastases. We investigated whether pre-treatment cerebral small vessel disease (cSVD) burden, particularly perivascular spaces (PVSs), is associated with RN risk.

This single-center retrospective study included 71 patients treated with fractionated SRT for brain metastases. RN was diagnosed by consensus using multiparametric MRI including DSC perfusion. Pre-treatment cSVD markers were evaluated according to STRIVE criteria, with PVSs graded using Potter's criteria in the basal ganglia (BG), centrum semiovale (CS), and midbrain (MB). Associations with RN were assessed using Firth's penalized logistic regression adjusted for age and sex.

RN developed in 33 patients (46.5%). Higher PVS grades in the CS were significantly associated with increased RN risk (grade 1: OR 6.35, 95% CI 1.86-21.72, p = 0.003; grade 2: OR 26.26, 95% CI 3.64-189.61, p = 0.001). Associations were also observed for higher PVS burden in the BG and MB, although these rested on small subsets with wide confidence intervals. Other cSVD markers showed no significant associations. Confidence intervals were wide due to sparse data in higher PVS grades.

This exploratory study suggests a potential association between pre-treatment PVS burden and RN risk. However, sparse data, wide confidence intervals, and the absence of lesion-level dosimetric adjustment limit conclusions. These preliminary findings warrant validation in larger, prospective cohorts with comprehensive dosimetric analysis.