Whole brain radiotherapy and simultaneous integrated boost: is it still a viable treatment for multiple brain metastases in the era of SRS?

Background: The objective of this study was to determine the outcomes of whole brain radiotherapy (WBRT) + simultaneous integrated boost (SIB) treatment in patients with multiple brain metastases. Materials and methods: 34 patients who were treated for multiple brain metastases with WBRT + SIB in two radiation oncology departments between 2014 and 2020 were evaluated retrospectively. Intracranial control and overall survival after radiotherapy (RT) were calculated with the Kaplan-Meier test. The prognostic factors of survival after RT were determined with Cox regression analysis. Results: The median age was 62 [interquartile range (IQR): 57–69] years. Median survival after cranial RT was 10 [95% confidence interval (CI): 7–13] months. One-year intracranial control probability after RT was 83%. Acute and late RT toxicity were observed in 2 patients. After 3 months of follow-up, 23 (68%) patients had complete/near complete response, 9 (26%) had partial response, and 2 (6%) had stable disease. In univariate analysis, the factors affecting survival after cranial RT were the presence of neurological symptoms (p = 0.003) and Karnofsky performance score (KPS, p = 0.001). The median survival of patients with and without neurological symptoms was 5 (95% CI: 4–6) months and 16 (95% CI: 5–27) months. Median survival of patients with KPS 60, 70, 80, and 90 were 1, 5, 10 and 13 months, respectively. In multivariate analysis, the only statistically significant prognostic factor was KPS [hazard ratio (HR): 0.94 95% CI: (0.89–0.99), p = 0.031]. Conclusions: WBRT + SIB is a well-tolerated technique with a promising 1-year intracranial control rate of 83% for patients with multiple brain metastases who were not amenable to surgery and/or SRS, particularly in good performance status (KPS > 70) and without neurologic impairments.