WBRT Plus SIB in Patients with Brain Metastases: Association with Longer Overall Survival and Safety Outcomes in a Single-Center Retrospective Analysis

Objective: To compare the efficacy, survival benefits, and safety of whole-brain radiotherapy (WBRT) alone versus WBRT combined with simultaneous integrated boost (WBRT+SIB) for patients with brain metastases. Methods: A total of 100 patients treated from 2017 to 2022 were retrospectively analyzed. Tumor response was assessed per RECIST 1.1. Survival differences were compared using the Kaplan–Meier method and log-rank test. Multivariate Cox regression and subgroup analyses were performed to evaluate the prognostic value and stability of WBRT+SIB. Results: The WBRT+SIB group exhibited numerically higher objective response and disease control rates without statistical significance. With a median follow-up of 31.0 months, WBRT+SIB significantly prolonged median overall survival (11.0 vs. 8.0 months, p = 0.011) and improved 1-, 2-, and 3-year survival rates. After adjusting for multiple confounders, WBRT+SIB independently reduced mortality risk (HR = 0.51, 95% CI: 0.27–0.97, p = 0.039). Subgroup analyses were exploratory; therefore, consistent survival advantages across strata cannot be confirmed. No significant differences in acute, subacute, or late neurotoxicity, including radiation-induced brain necrosis, were found between the two groups. Conclusions: WBRT+SIB was associated with longer overall survival compared with WBRT alone, without a significant increase in the incidence of radiotherapy-related adverse events. Although ORR and DCR were numerically higher in the WBRT+SIB group, these differences were not statistically significant. Given the limitations of this exploratory study, these findings should be considered hypothesis-generating and require validation in prospective randomized trials.