Clinical outcomes of daily 5-fraction Gamma Knife radiosurgery for large brain metastases: a retrospective cohort study

Purpose The Gamma Knife Icon has enabled hypofractionated Gamma Knife radiosurgery (GKRS) for large brain metastases (LBMs). We assessed the clinical outcomes and complications of daily 5-fraction GKRS for LBMs. Methods We enrolled 100 patients who underwent daily 5-fraction GKRS for LBMs (> 14 cm ³ ). Forty-six patients were male; the median age was 60 years. The median Karnofsky Performance Status (KPS) was 70 (60–100); 47 patients (47%) had pre-GKRS neurological deficits. The most common primary sites were lung (41), breast (24), and kidney (14). Median tumor volume was 22 cm ³ (14─70 cm ³ ) and the marginal dose was 35.2 Gy (50% isodose line) in 5 fractions. Median follow-up was 18 months (3─72 months). Results Local tumor control was observed in 74 cases (74%). The cumulative 1-, 2-, and 3-year control rates were 73%, 65%, and 60%, respectively. Eighty-six tumors achieved their best magnetic resonance imaging response within 1 year; the median volume reduction was 80% (22%─100%). Thirty patients (30%) had a dramatic volume reduction (> 95%). Median progression-free (PFS) and overall survival (OS) were 7.5 and 16.3 months, respectively. PFS was significantly associated with local tumor control ( p  = 0.008). OS was associated with pre-GKRS KPS and neurological deficits ( p  = 0.003 and p  = 0.025, respectively). Radiation necrosis occurred in 16 patients (16%); 9 (9%) were symptomatic and recovered fully with corticosteroids or bevacizumab. Conclusion Daily 5-fraction GKRS for LBMs yielded favorable local control and PFS with acceptable radiation necrosis rates, but OS benefit was uncertain. Prospective multicenter studies are warranted.