A retrospective review of SBRT for larger brain metastases or post-resection cavities: preliminary evidence from the Knight Cancer Institute

Objective Radiation for brain metastases is typically delivered by whole brain radiation (WBRT), stereotactic radiosurgery (SRS), or a combination thereof. There are patients with lesions that are not candidates for SRS owing to a maximum target diameter >3 cm, for which avoiding WBRT may provide a quality of life benefit. Here, we report our early experience with stereotactic hypofractionated radiation therapy for brain metastases or resection cavities (SBRT brain) as an alternative to WBRT. Methods We performed a single-institution retrospective review of 44 patients treated with SBRT brain between July 2007 and February 2012. Median lesion diameter was 3.65 cm. The most common fractionation was 30 Gy in five fractions. Treatments were delivered via BrainLAB/Varian NovalisTx linear accelerator with daily stereotactic x-rays for 6D setup correction, and cone-beam CT for validation. Results Mean follow-upwas 5.4months. Seventy-seven percent of patients underwent post-resection radiation. Median overall survival was 10 months. There was a trend for survival advantage in patients who underwent resection compared to the group with intact tumors, 10.8 versus 5.7 months (p=0.18), between systemic burden of disease and overall survival (p=0.06), and number of brain metastases (p=0.08). Twenty-seven percent had tumor recur locally, withmedian local recurrence-free survival of 21months. Local control did not stratify by BED10 (p=0.02), but did correlate with tumor size (p<0.001). Forty-three percent of patients failed elsewhere in the brain, with median recurrencefree survival of 9 months. Acute side effects were mild. Radionecrosis occurred in 14 %, with median onset of 41 months; a single patient was symptomatic requiring bevacuzimab. Conclusions SBRT brain for larger brain metastases and postresection cavities can be administered with a favorable side effect profile. Outcomes compare favorably to the historical data for WBRT. While longer-term survival was observed, inbrain failure and/or systemic disease progression are limiting overall survival.