Abstract 6503: Comparison of single-fraction stereotactic radiosurgery and surgical resection for brain metastases at least 4 cc in volume
Authors: Rahman Ahmad Ridwanur , Daugherty Emily , Hazama Ali , Ropri Ayesha , Formica Margaret , Shapiro Anna , Lacombe Michael , Chin Lawrence , Hahn Seung 
Published: September 2020

Abstract
Introduction:
Brain metastases are the most common intracranial malignancies and are typically treated with surgical resection, radiation therapy, or both. Small lesions can be treated safely and effectively with stereotactic radiosurgery (SRS) or surgery. However, this is not as well-defined for larger lesions still amenable to SRS or surgery. This study was conducted to retrospectively analyze SRS and surgery for brain metastases at least 4 cubic centimeters (cc) in volume.Methods:
We reviewed 177 patients with brain lesions ≥ 4 cc treated between March 2008 and July 2016 with either SRS (n = 123) or surgery (n = 54) for at least one malignant intracranial lesion. Patients were excluded if they had no follow-up records, had post-operative radiation, or had primary CNS malignancy on final pathology. Results:
Median follow-up time for all patients was 3.7 months. The SRS group had a greater proportion of non-small cell lung cancer (NSCLC) patients (p = 0.001), better ECOG performance status (PS) (p &lt; 0.001), and longer follow-up (4.7 vs 1.0 months respectively, p &lt; 0.001). Mean lesion volume was 8.5 ± 5.5 cc for SRS patients and 13.9 ± 11.0 cc for surgery patients (p = 0.05). Local recurrence rate (LR) was lower in patients treated with SRS compared to surgery (median time to LR not reached SRS v 5.8 months surgery; 1-year LR 25.5% v 76.8% respectively; p = 0.01). There was no significant survival difference between modalities (median survival 9.3 months SRS v 5.5 months surgery; 1-year overall survival (OS) 38.0% v 25.6% respectively; p = 0.22). Adverse events were comparable between the groups (21.2% SRS v 26.3% surgery, p = 0.76). Among patients with NSCLC, those treated with SRS had better PS (p = 0.003) and longer follow-up (5.0 v 0.7 months respectively, p = 0.001). LR was lower in NSCLC patients treated with SRS compared to surgery (median time to LR not reached SRS v 5.1 months surgery; 1-year LR 29.1% v 100.0% respectively; p = 0.03). Median and 1-year survival were higher for NSCLC patients treated with SRS (9.3 months SRS v 3.2 months surgery; 1-year OS 36.1% vs 0.0% respectively; p = 0.001). Similarly, for patients with PS 0-2, the SRS group had a greater proportion of NSCLC patients (p = 0.004) and a longer follow-up (4.6 v 0.6 months, p = 0.01); there were no significant differences in LR or OS for this subgroup. There were no significant differences in adverse events in either subgroup.Conclusions:
For brain metastases ≥ 4 cc in volume amenable to SRS or surgery, this study reports better LR with SRS compared to surgery alone. On subgroup analysis, patients with primary NSCLC histology experienced improved median and 1-year survival with SRS compared to surgery. However, differences in outcomes could be due to selection bias and warrants further investigation with better control of baseline characteristics.
Citation Format: Ahmad Ridwanur Rahman, Emily Daugherty, Ali Hazama, Ayesha Ropri, Margaret Formica, Anna Shapiro, Michael Lacombe, Lawrence Chin, Seung Hahn. Comparison of single-fraction stereotactic radiosurgery and surgical resection for brain metastases at least 4 cc in volume [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6503.