Stereotactic Radiosurgery of the Postoperative Resection Cavity for Brain Metastases

Purpose The purpose of this study was to analyze results of adjuvant stereotactic radiosurgery (SRS) targeted at resection cavities of brain metastases without whole-brain irradiation (WBI). Methods and Materials Patients who underwent SRS to the tumor bed, deferring WBI after resection of a brain metastasis, were retrospectively identified. Results Seventy-two patients with 76 cavities treated from 1998 to 2006 met inclusion criteria. The SRS was delivered to a median marginal dose of 18.6 Gy (range, 15–30 Gy) targeting an average tumor volume of 9.8 cm3 (range, 0.1–66.8 cm3 ). With a median follow-up of 8.1 months (range, 0.1–80.5 months), 65 patients had follow-up imaging assessable for control analyses. Actuarial local control rates at 6 and 12 months were 88% and 79%, respectively. On univariate analysis, increasing values of conformality indices were the only treatment variables that correlated significantly with improved local control; local control was 100% for the least conformal quartile compared with 63% for the remaining quartiles. Target volume, dose, and number of sessions were not statistically significant. Conclusions In this retrospective series, SRS administered to the resection cavity of brain metastases resulted in a 79% local control rate at 12 months. This value compares favorably with historic results with observation alone (54%) and postoperative WBI (80–90%). Given the improved local control seen with less conformal plans, we recommend inclusion of a 2-mm margin around the resection cavity when using this technique.