The Incidence of Brain Metastases in Correlation to Dominant Hemisphere and Different Brain Lobes

about the routine recommendation for this treatment without a proven survival benefit. One alternative approach to combined modality therapy is adjuvant SRS (A-SRS) to the post-surgical resection site. Studies of this approach, however, have failed to distinguish between true A-SRS and salvage SRS (S-SRS) to a surgical site that showed evidence of local recurrence prior to treatment. The goal of this retrospective study was to determine the effect of A-SRS to the tumor bed of completely resected BM. Our hypothesis was that A-SRS improves local control (LC) of BM compared to surgery alone or salvage SRS. Materials/Methods: From an institutional-review board approved database of patients receiving SRS at our institution, we identified patients who first underwent surgery for BM. Patients were stratified into two groups on a per lesion basis according to adjuvant treatment received: adjuvant SRS (A-SRS) or no-adjuvant SRS (NA-SRS). Patients with radiographic evidence of residual disease prior to A-SRS were excluded. LC was assessed using follow-up MRI studies and failure was defined as those surgical beds showing new enhancement consistent with tumor recurrence. Progression free survival was calculated from the date of surgery to the date of radiologic failure. LC and PFS were assessed using the Kaplan-Meier method. A subset of lesions in the NA-SRS cohort that developed local failure (LF) was treated with salvage SRS (S-SRS). LC in this subgroup was assessed using RECIST. Results: Between January 2009 and April 2014, 34 patients who underwent surgical resection of BM showed no evidence of residual disease after surgery. In these patients, there were a total of 39 lesions, classified as NASRS for 27 lesions or A-SRS for 12 lesions. The 6-month local control rate for tumors treated by NA-SRS was 43.5% and 90.9% for tumors treated with A-SRS (pZ0.024). Median progression free survival between NASRS and A-SRS was 129 days and 509 days, respectively (pZ0.025). Thirteen NA-SRS lesions developed LF on follow-up MRI and were treated with subsequent S-SRS. Analysis showed no significant difference in overall 6-month LC between the A-SRS group and the S-SRS group (90.9% vs. 100%, respectively, pZ0.112). Conclusion: A-SRS improves LC and PFS after surgical resection of BM even in the absence of radiographic evidence of residual disease. There was no significant benefit in overall LC when comparing pure adjuvant treatment to salvage SRS. Author Disclosure: A. Yaeh: None. T. Nanda: None. A. Jani: None. S. Saad: None. Y.H. Qureshi: None. K. Cauley: None. S.R. Isaacson: None. M.B. Sisti: None. J.N. Bruce: None. G.M. McKhann: None. A.B. Lassman: None. T.J. Wang: None.