Repeat Stereotactic Radiosurgery for Locally Recurrent Brain Metastases

PURPOSE/OBJECTIVES: The outcomes of repeat stereotactic radiosurgery (SRS) after failure of previous SRS are not well established. We report our overall experience using SRS for the retreatment of locally recurrent brain metastases. METHODS: Patients with brain metastases diagnosed between 2003 and 2015 who underwent repeat SRS for local tumor progression following prior SRS were identified. Rates of local control, radiation necrosis, and overall survival were analyzed. Factors affecting local failure and radiation necrosis were assessed by chi-square test. RESULTS: Twenty-four lesions in 22 patients underwent repeat SRS in a single fraction. Median age was 59 years. The median SRS-1 dose was 18 Gy, and the median SRS-2 dose was 15.5 Gy. The median SRS-1 target volume was 2.25 cm3, and the median SRS-2 target volume was 3.30 cm3. The median follow-up from SRS-2 was 8.8 months. The actuarial local controls for SRS-2 were 94.1% and 61.1% at 6 and 12 months, respectively. The incidences of actuarial radiation necrosis were 9.2% and 9.2% at 6 and 12 months, respectively. Volume of tumor > 4 cm3 correlated with increased risk of local failure (P = 0.006) with no local failures recorded with volumes similar to 4 cm(3). SRS-2 dose, cumulative SRS dose, receipt of whole brain radiotherapy, and use of SRS-2 as boost after surgery did not correlate with local failure or radiation necrosis. Median overall survival after SRS-2 was 8.78 months. CONCLUSION: Repeat SRS is feasible for select patients, particularly for those with tumor volume similar to 4 cm(3). Further evaluation is needed to establish the most appropriate treatment doses and volumes for this approach.