Abstract
The optimal treatment strategy following local recurrence after stereotactic radiosurgery (SRS) remains unclear. While upfront SRS has been extensively studied, few reports focus on outcomes after retreatment. Here, we report the results following a second course of SRS for local recurrence of brain metastases previously treated with SRS. Using institutional database, patients who received salvage SRS (SRS2) following in-field failure of initial SRS (SRS1) for brain metastases were identified. Radionecrosis and local failure were defined radiographically by MRI following SRS2. The primary endpoint was defined as the time from SRS2 to the date of all-cause death or last follow-up [overall survival (OS)]. The secondary endpoints included local failure-free survival (LFFS) and radionecrosis-free survival, defined as the time from SRS2 to the date of local failure or radionecrosis, or last follow-up, respectively. Twenty-eight patients with 32 brain metastases were evaluated between years 2004 and 2015. The median interval between SRS1 and SRS2 was 9.7 months. Median OS was 22.0 months. Median LFFS time after SRS2 was 13.6 months. The overall local control rate following SRS2 was 84.4%. The 1- and 2-year local control rates are 88.3% (95% CI, 76.7-100%) and 80.3% (95% CI, 63.5-100%), respectively. The overall rate of radionecrosis following SRS2 was 18.8%. On univariate analysis, higher prescribed isodose line (p = 0.033) and higher gross tumor volume (p = 0.015) at SRS1 were associated with radionecrosis. Although not statistically significant, there was a trend toward lower risk of radionecrosis with interval surgical resection, fractionated SRS, lower total EQD2 (<50 Gy), and lack of concurrent systemic therapy at SRS2. In select patients, repeat LINAC-based SRS following recurrence remains a reasonable option leading to long-term survival and local control. Radionecrosis approaches 20% for high risk individuals and parallels historic values.
Highlights
Brain metastases account for over half of brain tumors in adults [1,2,3]
Between 2004 and 2015, 11 females and 17 males received a second course of stereotactic radiosurgery (SRS) to 32 brain metastases initially treated with SRS
The optimal treatment strategy for recurrent brain metastases previously treated with SRS remains uncertain
Summary
Brain metastases account for over half of brain tumors in adults [1,2,3]. With increasing utilization of magnetic resonance imaging and improved systemic therapies, the incidence of brain metastases is increasing [2, 3]. The median survival for patients with brain metastasis has improved over time due to earlier detection, better brain-directed therapies, and more effective systemic therapies [4, 5]. Recent data suggest that stereotactic radiosurgery (SRS) alone is the preferred modality for individuals with one to three brain metastases [7], with some studies demonstrating favorable outcomes in individuals with greater than four brain metastases, especially younger individuals with limited extracranial disease [8, 9]. Stereotactic radiosurgery is an effective modality for treating brain metastases, delivered as either singular treatment or as adjuvant treatment after surgical resection, with 1-year local control rates approaching 90% [10, 11] and minimal toxicity [6, 12]. Data regarding the optimal treatment approach for these individuals are incredibly sparse
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