MMAP-09 CHARACTERISTICS CORRELATING WITH SURVIVAL IN PATIENTS TREATED FOR LARGE BRAIN METASTASES

BACKGROUND: We aimed to identify factors predicting survival following treatment to large (>4cc) BrM. METHODS: From a prospective registry database, we identified 364 adult patients treated for brain metastases (BrM) or surgical cavities larger than >4 cc: 127 and 237 treated with surgery plus stereotactic radiosurgery (S+SRS) and SRS alone, respectively. We compared the 2 treatment arms using propensity score-matched (PSMA) and multivariate analyses (MVA). P values <0.05 were considered statistically significant. RESULTS: Median target volume was 6.6cc (4-36.9cc) for intact BrM and 15cc (4-54) for cavities. Median OS was 19 and 12 months for the S+SRS and SRS groups, respectively [HR 1.73 (1.35-2.22) (P<0.001)]. On UVA, number of BrM [HR 1.13 (1.06-1.22) (P<0.001)], ECOG 3-4 [HR 2.78 (1.73-4.46) (P<0.001)], and extracranial disease (ECD) at BrM treatment [HR 1.82 (1.37,2.40) (P<0.001)], correlated inversely with OS. GPA [HR 0.61 (0.52,0.70) (P<0.001)] and receipt of systemic therapy after BrM treatment[HR 0.58 (0.45-0.75) (P<0.001)] correlated to improved OS. On MVA, S+SRS [HR 1.81 (1.19,2.74) (P<0.0054)], reduced target volume [HR 1.03 (1.01,1.06) (P<0.0042)], and receipt of immune/targeted therapy [HR 0.68 (0.50,0.93) (P<0.015)] correlated with OS. PSMA comparing the treatment arms matched by ECD, number of BrM, ECOG, and SRS target volume, demonstrated that treatment arm remained correlated to OS [HR 1.62 (1.20-2.19) (P=0.0015)]. The cumulative incidence (CI) of LF requiring surgical resection at 12 months was 3% versus 7% for S+SRS and SRS groups, respectively [(HR 2.04 (0.89-4.69) (P =0.091)]. CI of PMD at 12 months was 16% versus 0% for S+SRS and SRS groups, respectively. CONCLUSION: Reduced SRS target volume, treatment with systemic therapy following BrM treatment, and surgical resection prior to SRS correlate with survival in patients with large BrM. PMSA supports the hypothesis that surgery prior to SRS improves survival in patients with large BrM.