Abstract
PURPOSE
To examine outcomes in patients undergoing linear accelerator (LINAC) based fractionated stereotactic radiosurgery (fSRS) to 30 Gy in 5 fractions.
METHODS
We completed a retrospective review of patients with brain metastases treated with 5-fraction LINAC fSRS at Phelps Health. All patients with CNS metastatic disease treated with fSRS were included in the study. Incidence of symptomatic radionecrosis (sRN), local brain failure (LBF), time to death, target volume and dose, prior whole brain radiotherapy (WBRT), prior surgical resection, and concurrent immunotherapy were assessed. sRN was defined as grade 2 or higher per CTCAE v4.0.
RESULTS
From 2016–2019, 28 patients and 60 lesions were treated. The most common metastasis histology was non-small cell lung cancer (n = 22), renal cell carcinoma (n = 12), and melanoma (n = 11). Median follow-up time was 6.49 months (range 0.33 – 23.96). Of 60 lesions, three lesions developed sRN and one asymptomatic patient developed radiographic evidence of radiation necrosis. Mean GTV was 1.03cm3 in patients with sRN. Of 57 lesions without sRN, median GTV was 1.45cm3 (range 0.11 - 20.1). Mean time to sRN was 3.17 months. Two symptomatic patients received prior WBRT. One symptomatic patient received concurrent immunotherapy. No symptomatic patients had surgical resection prior to fSRS. Among 24 lesions without prior radiation, 1 (4.2%) developed sRN. 10 lesions underwent surgical resection prior to fSRS with none developing sRN. 34 lesions were treated with concurrent immunotherapy and one developed sRN (2.9%). Local failure occurred in 9 lesions (15%). Median time to death for all patients was 4.50 months (range 1.02 - 19.40).
CONCLUSIONS
fSRS to 30 Gy in 5 fractions has promising efficacy with low incidence of sRN in treatment of CNS metastatic disease. Further investigation is required to determine predictors in patient outcome.