How safe and effective is radiosurgical treatment for patients with 10 or more BM?

Background We evaluated the outcome of radiosurgically treated patients with ≥10 brain metastases (BM), compared to patients <10 BM. Methods Patients, who underwent at least one Gamma Knife radiosurgical (GKRS) treatment for at least one BM without previous CNS treatments, were retrospectively divided into two groups: 1) <10 or 2) ≥10 BM. Results At GKRS1, 1293 patients had <10 BM and 126 patients had ≥10 BM. The estimated median survival after GKRS1 was significantly longer in patients with <10 BM (9.9 months), compared to patients with ≥10 BM at GKRS1 (5.3 months; p < 0.001). Age >65 years (p < 0.001), male sex (p = 0.001), Karnofsky Performance Status Scale <80 (p < 0.001), presence of extracranial metastases (p = 0.008), presence of neurological symptoms (p = 0.019), a cumulative BM volume of all BM treated at GKRS1 ≥10 cm3 (p = 0.017), no concomitant immunotherapy or targeted therapy at GKRS1 (p < 0.001), and the number of ≥ 10 BM at GKRS1 (p < 0.001), were identified as independent prognostic factors for an increased risk of death. In patients with ≥10 BM, poor clinical condition, a cumulative BM volume of all BM treated ≥25 cm3, and no concomitant immunotherapy or targeted therapy at GKRS1 were identified as significant independent prognostic factors. The occurrence of post-radiosurgical complications and local tumor control did not differ between the groups. Conclusions In addition to BM count, multiple factors may influence survival and should be considered during the pre-radiosurgery assessment. GKRS represents a safe and effective first-line treatment method even for patients with ≥10 BM, particularly in the era of modern systemic therapies.