Efficacy of 3D-TSE Sequence-based Radiosurgery in Prolonging Time to Distant Intracranial Failure: A Session-wise Analysis in a Histology-Diverse Patient Cohort

Stereotactic radiosurgery (SRS) for patients with brain metastases (BM) is associated with a risk of distant intracranial failure (DIF). This study evaluates the impact of integrating dedicated 3D-TSE sequences to MPRAGE in BM detection and DIF prolongation in a histology-agnostic patient cohort. The study population included adults treated with SRS from February 2019 to January 2024 who underwent MPRAGE alone or dual-sequence with the addition of 3D-TSE starting from February 2020. Median times to DIF were estimated using the Kaplan-Meier method. The 216 study patients who underwent 332 SRS courses for 1456 BM imaged with MPRAGE and 3D-TSE (primary cohort) were compared to a control cohort (92 patients, 135 SRS courses, 462 BM). In the session-wise analysis, the median time to DIF between the cohorts was significantly prolonged in the primary vs. control cohorts (11.4 vs. 6.8 months, p=0.029), more pronounced in the subgroups with 1-4 metastases (14.7 vs. 8.1 months, p=0.008) and with solitary BM (36.4 vs. 10.9 months, p=0.001). While patients relapsing on immunotherapy or targeted therapy did not significantly benefit from 3D-FSE (7.2 vs. 5.7 months, p=0.280), those who relapsed on chemotherapy or who were off systemic therapy (including synchronous metastases) exhibited a trend towards longer time to DIF with 3D-TSE integration (14.7 vs. 7.9 months, p=0.057). Implementing 3D-TSE sequences into SRS practice increases BM detection across all patients and translates into clinical relevance by prolonging time to DIF, particularly in those with limited intracranial disease and those not receiving CNS-active agents.