Explore the scholarly record.

Abstract

Abstract Background Local recurrence after stereotactic radiosurgery (SRS1) for brain metastases remains a therapeutic challenge, and optimal re-irradiation parameters are not well defined. This study evaluated local control (LC) and predictors of radiation necrosis (RN) following repeat stereotactic radiosurgery (SRS2) for previously irradiated brain metastases. Methods This retrospective study included patients treated with SRS2 for locally recurrent brain metastases after prior SRS1. Patients who had received whole-brain radiotherapy were excluded. Follow-up MRI scans were reviewed for LC and RN according to RANO criteria. Kaplan–Meier analysis was used for LC and RN-free survival. Cox regression analysis identified predictive factors. ROC curve analysis determined optimal dosimetric cut-off values. Results Forty patients with 59 locally recurrent brain metastases treated with SRS2 to the same lesion were analyzed. Median follow-up was 11 months (range, 2–83). Median SRS2 prescription dose was 24 Gy (range, 14–35) delivered in a median of 3 fractions (range, 1–5), and median GTV diameter was 2.1 cm (range, 0.3–7.6). One-year local progression-free survival was 57.5% while one-year RN-free survival was 80%. Higher SRS2 EQD 2 (10) (> 33.6 Gy; 63.8% vs 93.1%, p = 0.007), cumulative EQD 2 (10) (> 75 Gy; 63.2% vs 91.4%, p = 0.006), SRS2 BED 10 (> 83.7 Gy; 65.8% vs 90.9%, p = 0.013), and cumulative BED 10 (> 177 Gy; 65.2% vs 91.0%, p = 0.013) were associated with significantly increased RN risk without corresponding LC benefit. Age, sex, histology, location, prior surgery, GTV and PTV diameter and volume, SRS1–SRS2 interval, dosimetric indices, and systemic therapy were not significantly associated with LC or RN. Conclusions Repeat SRS is an effective and well-tolerated salvage treatment for locally recurrent brain metastases. Doses below the identified BED and EQD 2 thresholds were associated with a lower risk of RN without significantly compromising local control. Prospective studies are warranted to validate optimal re-SRS dose constraints and treatment strategies for recurrent brain metastases.