Introduction: To determine predictive parameters of radiation induced imaging changes suggestive of radiation necrosis and the incidence of neurologic complications in patients with metastatic brain lesions treated with stereotactic radiosurgery (SRS).
Methods: 127 patients with metastatic brain lesions underwent CRW framed LINAC based SRS between 2007-2010. 62 patients who had no retreats and 2 months or greater follow up including neurologic assessment and repeat imaging were included in this study. Follow up MR imaging was fused with the original treatment planning scans and area of radiation necrosis was contoured. Volumes of normal brain receiving 8, 10 and 12 Gy (V8, V10, V12); V100, D100, Conformality Index (CI) and tumor volumes were looked at as predictive factors for necrosis.
Results: 16 patients (23 lesions) had radiographic evidence of necrosis on follow up imaging. Of the 16 patients with radiation necrosis, 5 patients (31%) had neurologic sequelae including hemiparesis, dysphonia, writing difficulties and gait disturbances. In patients showing radiographic evidence of necrosis, mean V8, V10 and V12 were: 17.1±18.1, 12.2cm3±12.5, and 8.9 cm3±9.1, respectively as compared to 8.4 cm3 ± 5.8, 6.0cm3 ± 4.2, and 4.4 cm3 ± 3.0, respectively in patients without necrosis. This difference was statistically significant (p=0.04). Higher D100 was significantly correlated with symptomatic radiation necrosis (p=0.04).
Conclusions: In our patients higher V12, V10, and V8 correlated with greater risk of radiographic radiation necrosis. D100 correlated with higher likelihood of developing symptomatic radiation necrosis. Since we included patients with multiple lesions and no retreatment, confounding variables such as co-morbid conditions, histology and concomitant therapies have less likelihood of affecting the analysis. Inclusion of these parameters in SRS planning is strongly suggested.
Patient Care: This research hopes to provide a set of predictive parameters for the development of radiation necrosis as well as the development of symptomatic radiation necrosis, which may be deleterious to the patient. This will allow the physician to tailor their treatment plan accordingly and decrease toxicity.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) understand the importance of the volume and dose parameters in an SRS plan and how it relates to the development of radiation necrosis, 2) understand radiation necrosis may be symptomatic or asymptomatic, 3) recognize that large V12, V10, and V8 correlate with the risk of developing radiation necrosis and SRS plans with large D100 correlate with symptomatic radiation necrosis.