Dedicated Isotropic 3-D T1 SPACE Sequence Imaging for Radiosurgery Planning Improves Brain Metastases Detection and Reduces the Risk of Intracranial Relapse

Abstract

<h3>Purpose/Objective(s)</h3> Stereotactic radiosurgery (SRS) is increasingly used for patients with brain metastasis, yet the risk of distant intracranial failure (DIF) continues to be the principal disadvantage of this focal approach. The objective of this study was to determine if advanced dedicated treatment planning images at SRS would improve lesion detection and consequentially reduce DIF. <h3>Materials/Methods</h3> Patients treated with SRS at a single tertiary care institution underwent dedicated treatment planning MRIs including a standard three-dimensional (3D) magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequence as well as an optimized 3D sampling perfection with application-optimized contrasts using different flip angle evolutions (SPACE) sequence from 02/2020-01/2021. DIF was calculated using the Kaplan-Meier method and comparisons were made to a historical consecutive cohort of patients treated using MPRAGE alone (02/2019-01/2020). <h3>Results</h3> 134 patients underwent 170 SRS courses for 821 brain metastases imaged with both MPRAGE and SPACE (primary cohort). MPRAGE sequence evaluation alone detected 679 (82.7%) lesions. With neuroradiologists evaluating SPACE and MPRAGE, an additional 108 lesions were identified (p<0.001). Upon multidisciplinary review, 34 (4.1%) additional lesions were identified. Compared to the historical cohort (103 patients, 133 SRS courses, 479 brain metastases) treated using MPRAGE alone, patients treated using MPRAGE and SPACE had improved median time to DIF (13.5 vs. 5.1 months, <i>p</i>=0.004). The benefit was even more pronounced for patients treated for their first SRS course (18.4 vs. 6.3 months, <i>p</i>=0.001). On multivariate analysis, factors associated with improved DIF included stable extracranial disease, better performance status, using MPRAGE and SPACE images, and being treated for first course SRS (all <i>p</i><0.05). SRS using MPRAGE and SPACE was associated with a 60% reduction in risk of DIF compared with a historical cohort using MPRAGE alone (HR: 0.40; 95%CI: 0.28, 0.57, <i>p</i><0.001). <h3>Conclusion</h3> Among patients with brain metastasis treated with SRS, the addition of a dedicated treatment planning SPACE sequence to MPRAGE substantially improved detection of brain metastasis compared to MPRAGE alone. This approach was associated with a statistically significant and clinically meaningful prolongation in time to DIF, especially for patients undergoing their first course of SRS.