Locl-13 surgical resection plus stereotactic radiosurgery (srs) versus srs alone for large posterior fossa brain metastases: outcomes and factors guiding the decision of treatment modality

Abstract INTRODUCTION Approximately 20% of brain metastases (BM) occur in the posterior fossa (PF). However, the criteria to treat large PF BM with surgery (S) followed by stereotactic radiosurgery (SRS) or SRS alone are still unclear. We aim to identify parameters that can help in the decision of treating PF BM with S+SRS or SRS and to compare outcomes between the two groups. METHODOLOGY We reviewed a prospective registry database (2009 to 2020) and identified all patients with PF BM (≥4cc in volume) treated with SRS or S+SRS. Clinical and radiological, parameters were analyzed. We examined two endpoints: Overall Survival (OS) and Local Failure (LF). RESULTS 64 patients were identified; 30 were treated with S+ SRS and 34 with SRS. Gait imbalance and Intracranial pressure symptoms were significantly different between the groups; 97% and 80% for S+SRS vs 47% and 35% for SRS, respectively. Radiologically, there were significant differences in the mean volume of the lesions [6.7 cm3 in SRS vs 29.8cm3 in S+SRS cohort] (p<0.001), compression of the IV ventricle (47% in SRS vs 96% in S+SRS cohort, (p<0.001)) and hydrocephalus (0% in SRS vs 29% in S+SRS cohort, (p<0.001)). One surgical patient required salvage SRS and two SRS patients required salvage S. Patients with S+SRS (HR 0.35, p<0.001) and higher GPA scores (HR 0.62, p=0.007) correlated with better OS. There was no significant difference in rates of LF between the 2 groups. CONCLUSIONS Patients treated with S+SRS were more likely to be symptomatic, have larger tumors, and have compression of the IV ventricle with hydrocephalus. Non-symptomatic patients with moderately sized lesions were safely managed with SRS. S+SRS treatment and higher GPA were associated with improved OS.