1337 The Impact of Brain Metastasis Multiplicity on Postoperative Survival and CNS Progression: A Single Center Study

INTRODUCTION: The prognosis of patients with brain metastasis (BM) depends on patient and disease-specific factors. Intracranial disease burden may be associated with postoperative outcomes such as survival and CNS tumor progression, although the extent of this association has not been clearly elucidated. METHODS: This was a retrospective, single-center cohort study including patients who underwent BM resection over a 20-year period. Patients with a single BM and those with multiple BMs at time of craniotomy were grouped separately. Outcomes included overall survival, time to CNS progression, and medical/surgical complications postoperatively. RESULTS: The cohort consisted of 251 and 228 patients with a single BM or multiple BM at the time of surgery, respectively. Patients with single BM were older compared to those with multiple BMs, were more likely to be from breast cancer and non-small cell lung cancer, and were less likely to have undergone prior checkpoint inhibitor therapy or radiation therapy. Patients with multiple BMs had a significantly shorter overall survival from surgery compared to patients with single BM (median 1.2 vs 1.9 years, Log-rank p=0.0005) which was confirmed in a multivariable Cox proportional hazards model (HR=1.5, 95% CI: 1.2-1.9, p=0.0015). Patients with multiple BM had a shorter time to distant CNS progression (median 0.8 vs 2.2 years, Log-rank p<0.0001) and was further confirmed in a multivariable Cox proportional hazards model (HR=1.5, 95% CI: 1.1-2.1 p=0.0142). There were no differences in local progression or complications between the two groups. CONCLUSIONS: Multiplicity of BM at time of craniotomy is a predictor of survival and distant progression but does not impact local progression or complication rates.