Surgical bed stereotactic radiotherapy of brain metastases: Clinical outcome and predictors of local and distant brain failure

Abstract

PurposeTo retrospectively analyze the outcomes of stereotactic radiotherapy (SRT) targeted at surgical bed of brain metastases (BM) and identify patterns of local/distant brain relapses (LR/DBR). Patients/methodsSeventy patients were treated with SRT between 2008–2017. Marginal dose prescription on the 70% isodose line depended on the maximal diameter of the target volume and range between 15–18Gy for single fraction radiosurgery and 23.1–26Gy in 3–5 fractions for fractionated SRT. ResultsAt 12 months, the overall survival (OS) was 69% [CI 95%=59%–81%]. At 6 and 12 months, the cumulative incidence functions (CIF) of local relapse were 4% [1%–13%] and 15% [8%–26%], respectively. According to univariate analysis, factors associated with LR were an initial volume larger than 7cc (hazard ratio: 4.6 [1.0–20.8], P=0.046) and a positive resection margin [hazard ratio: 3.6 [1.1–12.0], P=0.037. DBR occurred in 54.3% of patients with a median time of 8 months. None of the variables tested (histology, location or number of lesions) were found correlated with the DBR. Leptomeningeal disease occurred in 12.9% of cases. Salvage whole brain radiotherapy (WBRT) was required in 45.7% of patients and delayed by a median time of 9.6 months. Symptomatic radionecrosis (RN) occurred in 7.1%. ConclusionsAdjuvant SRT was an effective and well-tolerated treatment to control the postoperative risk of recurrence of BM without compromising OS. Positive resection margins and large volumes were predictors factor of local relapse.