Performance of Brain Metastasis Velocity and Initial Brain Metastasis Velocity in a Latin American LINAC-Based Stereotactic Radiosurgery Cohort

Purpose: Brain metastasis velocity (BMV) and initial brain metastasis velocity (iBMV) have been proposed as dynamic metrics to describe intracranial metastatic behavior in patients treated with stereotactic radiosurgery (SRS). However, their prognostic relevance in linear accelerator (LINAC)-based practice and Latin American populations remains incompletely characterized. Methods: We performed a retrospective cohort study of adult patients with brain metastases (BMs) treated with LINAC-based SRS between 2020 and 2025. iBMV was defined as the number of brain metastases at first SRS divided by the time from primary cancer diagnosis to intracranial metastasis detection. BMV was calculated in patients who developed distant brain failure (DBF) as the rate of new metastases from initial SRS to first DBF. Overall survival was analyzed using Kaplan–Meier estimates and Cox proportional hazards modeling. Results: The iBMV cohort included 127 patients, of whom 62 developed DBF and were evaluable for BMV analysis. iBMV did not significantly stratify overall survival. In contrast, BMV demonstrated a strong association with survival following DBF. Patients with low BMV experienced significantly prolonged survival compared with intermediate and high BMV groups. BMV remained independently associated with survival after adjustment for relevant clinical covariates. Conclusions: Within this contemporary LINAC-based Latin American cohort, BMV provided clinically meaningful prognostic information after intracranial progression, whereas iBMV did not confer prognostic value at initial presentation. Incorporation of BMV may improve post-progression risk stratification and inform salvage treatment strategies.