Introduction: Stereotactic radiosurgery to a surgical cavity(SRS-cav) to improve local control(LC) after resection of brain metastases(BM) is an alternative to adjuvant whole brain radiotherapy(WBRT). There is limited prospective data regarding efficacy of SRS-cav for LC.
Methods: Patients with 1-3 BMs with complete resection of at least one were randomized to SRS-cav or observation(OBS) of the cavity(ies). We stratified by number of BMs, histology, and volume. Unresected BMs were treated with SRS. The primary endpoint was failure of LC. Secondary endpoints included overall survival(OS), distant BM(DBM), complications and WBRT. The study was designed with 80% power to detect a HR of 0.6 assuming a two-sided 5% alpha and 50% LC at 6 mo in the OBS arm.
Results: From 10/2009 to 10/2015, 131 patients with 140 resected BMs were randomized to SRS-cav(n=64) or OBS(n=67). 34 and 28 additional BMs were treated in the SRS-cav and OBS arms, respectively. Median follow-up was 12.6 mo(range 0.3-70.6 mo). LC rates were superior in the SRS-cav group(HR 0.46: 95%CI 0.25, 0.85, p=0.011). LC rates for SRS-cav and OBS were 83% vs 57% at 6mo and 72 % vs 45% at 12mo, respectively. No significant SRS-cav complications were noted. DBM rate at 12mo was 43% vs 33% in the SRS-cav vs OBS groups, respectively,(HR 0.79,95%CI 0.50,1.24,p=0.29). 24 SRS-cav and 30 OBS patients required WBRT(median time to WBRT of 16.1 and 15.2mo, respectively, HR 0.8,95%CI 0.5,1.4, p=0.42). Median OS was 17mo in both arms(HR 1.22,95% CI 0.79,1.87,p=0.37). On multivariate analysis, histology, lesion number, systemic disease status or GPA did not affect LC. Use of SRS-cav(HR 0.4,95% CI 0.2,0.8) was associated with better LC and pre-operative tumor>3 cm(HR 2.4,95% CI 1.2,4.9) was associated with worse LC.
Conclusions: SRS to a surgical cavity improves LC compared to observation alone for BM. OS and DBM were not affected by the use of SRS.
Patient Care: We expect that our results from a prospective randomized trial will alter the current standard of care for the treatment of brain metastasis. Specifically, the routine use of whole brain radiation may be abandoned for the treatment of oligometastatic brain disease. Further, complete surgical resection of smaller brain tumors may be followed with close observation rather than adjuvant radiation.
Learning Objectives: 1. Understand the utility of SRS in improving LC after resection of a brain metastasis
2. Understand the importance that size plays in predicting local recurrence after resection of brain metastases.
3. Appreciate the value of SRS as an alternative to WBRT for the treatment of metastatic brain tumors after surgical resection.