(SS#I) Rosenblum-Mahaley Clinical Research award (2023 Award Winner): GRASP Dynamic Contrast-enhanced MRI Can Assist in Distinguishing Brain Metastasis Progression from Radiation Effects After Stereotactic Radiosurgery

Introduction: Differentiating brain-metastasis (BM) progression from radiation effects or necrosis (RN) remains challenging. Golden-angle radial sparse parallel (GRASP) dynamic contrast-enhanced MRI provides high spatial and temporal resolution to analyze tissue enhancement, which may differ between tumor progression (TP) and RN. We investigated the utility of longitudinal GRASP MRI in distinguishing TP from RN following gamma-knife stereotactic radiosurgery (SRS).

Methods: We retrospectively evaluated 48 patients with BM managed with SRS at our institution from 2013-2020 who had GRASP MRI before and at least once after SRS. TP (n=16) was pathologically confirmed. RN (n=16) was diagnosed on either resected tissue without evidence of tumor or on lesion resolution on follow-up. As a reference, we included a separate group of non-small lung cancer patients that showed favorable response with tumor control and without RN on subsequent imaging (n=16). Mean contrast wash-in and wash-out slopes normalized to the superior sagittal sinus were compared between groups. Receiver-operating characteristic analysis was performed to determine diagnostic performance.

Results: After SRS, progression showed a significantly steeper wash-in slope than RN on all three follow-up scans (scan 1: 0.29±0.16 vs. 0.18±0.08, p=.021; scan 2: 0.35±0.19 vs. 0.18±0.09, p=.004; scan 3: 0.32±0.12 vs. 0.17±0.07, p=.002). No significant differences were found in the post-SRS wash-out slope. Post-SRS wash-in slope differentiated progression and RN with AUC 0.74, sensitivity 75%, specificity 69% on scan 1; AUC 0.85, sensitivity 92%, specificity 69% on scan 2; and AUC 0.87, sensitivity 63%, specificity 100% on scan 3.

Conclusion : Longitudinal GRASP MRI may help to differentiate metastasis progression from RN.