Objective • Stereotactic radiotherapy (SRt) has been increasingly used for treatment of brain metastases in recent years. the goal of this study was to evaluate the clinical outcomes in patients with brain metastases treated with LINAC-based SRt.

Methods • Patients who underwent SRt at our institution between 2013 and 2017 were retrospectively analyzed. treatment plans were generated using either iPlan stereotactic treatment planning system (Brainlab Ag, Feldkirchen, Germany) or Eclipse v11.0.47 (varian Medical Systems, Palo Alto, CA, USA) and patients were treated on a trueBeam machine equipped with a robotic couch. the treatment response was assessed using RANOBM criteria. the primary endpoint was local control. Secondary endpoints were distant brain control, overall survival and treatment toxicity. Results • Fifty-six patients (28 males and 28 females) with 100 lesions were identified for this study from July 2013 to November 2017. the median age at the time of SRt was 65 years (range 16-86). the most common histologies were lung (66%) and breast (26%). Seventeen lesions (17%) were treated postoperatively. Median GPA score (graded prognostic assessment) was 2.5. treatment regimens consisted of: 1 fraction (median dose = 20 Gy), 3 fractions (median dose = 27 Gy), 5 fractions (median dose = 30 Gy) and 6 fractions (median dose = 30 Gy) in 27%, 18%, 41% and 14% of the lesions respectively. the median Gtv size was 2.44cc (range 0.1-119.67cc) and the median Ptv size was 5.03cc (range 0.32-197.22cc). At a median follow-up of 9.4 months, 7 patients recurred locally. the 1-year local control rate was 88% and the mean local control was 33 months. the 1-year and mean distant brain control were 45% and 16.8 months respectively and the 1-year and mean overall survival were 70% and 29.5 months respectively. A GPA score > 2 was significantly associated with better overall survival than a GPA score ≤ 2 (p = 0.013). Brain radionecrosis occurred in 4 patients (7%), being symptomatic in 2 patients.

Conclusion • Our institution experience showed that LINAC-based SRt is an effective local ablative treatment for brain metastases with an excellent toxicity profile.

Keywords: stereotactic radiotherapy; brain metastases; toxicity; overall survival

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