Gamma Knife Radiosurgery Results for Patients With 10-19 Versus ≥20 Brain Metastases: Retrospective Studies of 1482 Cohort and 936 Matched Patients (JLGK2107 Study)

Abstract Background and purpose The role of stereotactic radiosurgery (SRS) for patients with ≥20 brain metastases (BMs) is not fully understood as yet. We compared SRS treatment results for ≥20 versus 10-19 BMs. Materials and methods This IRB-approved, retrospective cohort study used our prospectively accumulated database including 1482 patients (906 with 10-19 BMs, 576 with ≥20 BMs) treated with gamma knife SRS during a 20-year period (1998-2018). Results Because there was considerable bias in pre-SRS clinical factors between the two groups, a case-matched study was conducted and 936 (468 in each of the two groups) patients were selected for this study. The post-SRS median survival time in patients with ≥20 BMs, 5.9 (95% CI; 5.1-6.8) months, was the same as that in patients with 10-19 BMs, 5.9 (95% CI; 5.2-7.2) months. Crude and cumulative incidences of neurological death, neurological deterioration, local recurrence, repeat SRS, salvage whole brain radiotherapy and SRS-related complications, as determined by competing risk analyses, did not differ significantly between the two tumor number groups. Univariable analyses of these 1482 patients demonstrated female gender, Karnofsky Performance Status ≥80%, neurologically asymptomatic, synchronous presentation, controlled primary cancer and no extra-cerebral metastases to be factors significantly favoring longer survival in both the 10-19 and the ≥20 BM groups. To minimize the complication risk, either cumulative or the largest BM volume ≤10 mL and minimum dose ≤20.00 Gy should be taken in consideration when planning treatment. Conclusions We conclude that carefully-selected patients with ≥20 tumors are not unfavorable candidates for SRS alone.