Background: Surgical resection remains the standard treatment for large brain metastases (LBMs), but many patients are not surgical candidates due to poor performance status or uncontrolled systemic disease. Gamma Knife-based hypofractionated stereotactic radiotherapy (GKRS) has emerged as a potential alternative; however, its clinical role in this population remains insufficiently defined. We evaluated whether a uniform daily 5-fraction GKRS provides effective and safe local treatment for surgery-ineligible LBMs.
Methods: We retrospectively analyzed 100 patients with LBMs (>14 cm3) who underwent primary hypofractionated GKRS using a uniform daily 5-fraction schedule. Forty-six patients were male; the median age was 60 years. The median Karnofsky Performance Status (KPS) was 70 (60-100); a total of 47 patients (47%) had pre-GKRS neurological deficits. The most common primary sites were lung (41), breast (24), and kidney (14). The median tumor volume was 22.0 cm3 (14-70 cm3), and the marginal dose was 35.2 Gy (50% isodose line) in 5 fractions. The primary endpoints included local tumor control (LTC), intracranial progression-free survival (PFS), and overall survival (OS). Radiation necrosis (RN) was assessed as a key safety outcome.
Results: At a median follow-up of 18 months, the overall LTC rate was 74%, with 1-, 2-, and 3-year rates of 73%, 65%, and 60%, respectively. Median PFS and OS were 7.5 and 16.3 months. Higher pre-treatment KPS and absence of neurological deficits were independently associated with improved OS (p = 0.003 and 0.025, respectively). RN occurred in 16% of patients, with 9% developing symptoms; all symptomatic cases were effectively managed with corticosteroids or bevacizumab. Most tumors demonstrated substantial volumetric reduction, with a median decrease of 80% and 30% achieving near-complete response (>95%).
Conclusions: A uniform daily 5-fraction hypofractionated GKRS provides effective local control with acceptable toxicity in patients with LBMs. These findings support its role as a feasible local treatment option in selected patients who are not candidates for surgery. Integration with systemic therapies and prospective validation are warranted to refine patient selection and optimize outcomes.
Keywords: Gamma Knife; brain metastases; hypofractionated radiosurgery; radiation necrosis; stereotactic radiotherapy; surgery-ineligible.